The ratio of the mass of water vapor to
the volume occupied by a mixture of
water vapor and dry air.
material that extracts one or more
substances from a fluid (gas or liquid)
medium on contact, and which changes
physically and/or chemically in the
process. The less volatile of the two
working fluids in an absorption cooling
component of a solar thermal collector
that absorbs solar radiation and
converts it to heat, or, as in a solar
photovoltaic device, the material that
readily absorbs photons to generate
charge carriers (free electrons or
passing of a substance or force into the
body of another substance.
A type of air cooling device that uses
absorption cooling to cool interior
Coefficient In reference to a solar
energy conversion devices, the degree to
which a substance will absorb solar
energy. In a solar photovoltaic device,
the factor by which photons are absorbed
as they travel a unit distance through a
A process in which cooling of an
interior space is accomplished by the
evaporation of a volatile fluid, which
is then absorbed in a strong solution,
then desorbed under pressure by a heat
source, and then recondensed at a
temperature high enough that the heat of
condensation can be rejected to a
Refrigeration A system in which a
secondary fluid absorbs the refrigerant,
releasing heat, then releases the
refrigerant and reabsorbs the heat.
Ammonia or water is used as the vapor in
commercial absorption cycle systems, and
water or lithium bromide is the
Absorptivity In a
solar thermal system, the ratio of solar
energy striking the absorber that is
absorbed by the absorber to that of
solar energy striking a black body
(perfect absorber) at the same
temperature. The absorptivity of a
material is numerically equal to its
Access Charge A fee
levied for access to a utilitys
transmission or distribution system. It
is a charge for the right to send
electricity over anothers wires and is
not typically tied to the actual amount
of power shipped.
component of a heat pump that stores
liquid and keeps it from flooding the
compressor. The accumulator takes the
strain off the compressor and improves
the reliability of the system.
Acid Rain A term
used to describe precipitation that has
become acidic (low pH) due to the
emission of sulfur oxides from fossil
fuel burning power plants.
Activation energy of a reaction is the
amount of energy needed to start the
Active Cooling The
use of mechanical heat pipes or pumps to
transport heat by circulating heat
Active Heating System
A solar water or spaceheating system
that moves heated air or water using
pumps or fans.
Active Power The
power (in Watts) used by a device to
produce useful work. Also called input
Active Solar Heater
A solar water or space-heating system
that use pumps or fans to circulate the
fluid (water or heat-transfer fluid like
diluted antifreeze) from the solar
collectors to a storage tank subsystem.
loss or gain of heat to a system. An
adiabatic change is a change in volume
and pressure of a parcel of gas without
an exchange of heat between the parcel
and its surroundings. In reference to a
steam turbine, the adiabatic efficiency
is the ratio of the work done per pound
of steam, to the heat energy released
and theoretically capable of
transformation into mechanical work
during the adiabatic expansion of a unit
weight of steam.
Drive An electronic device that
controls the rotational speed of
motor-driven equipment such as fans,
pumps, and compressors. Speed control is
achieved by adjusting the frequency of
the voltage applied to the motor.
Adobe A building
material made from clay, straw, and
water, formed into blocks, and dried;
used traditionally in the southwestern
Microorganisms that require free oxygen,
or air, to live, and that which
contribute to the decomposition of
organic material in soil or composting
entity that brings together customers
into a buying group for the purchase of
a commodity or service. The vertically
integrated investor owned utility,
public utility districts, municipal
utilities, and rural electric
cooperatives perform this function in
todays power markets. Other entities
such as buyer cooperatives or brokers
could perform this function in a
restructured power market. This is not
to be confused with a marketer, which is
an entity that represents different
Air The mixture of
gases that surrounds the earth and forms
its atmosphere, composed of, by volume,
21 percent oxygen, 78 percent nitrogen.
Air Change A
measure of the rate at which the air in
an interior space is replace by outside
(or conditioned) air by ventilation and
infiltration; usually measured in cubic
feet per time interval (hour), divided
by the volume of air in the room.
Air Collector In
solar heating systems, a type of solar
collector in which air is heated in the
Air Conditioner A
device for conditioning air in an
interior space. A Room Air Conditioner
is a unit designed for installation in
the wall or window of a room to deliver
conditioned air without ducts. A Unitary
Air Conditioner is composed of one or
more assemblies that usually include an
evaporator or cooling coil, a compressor
and condenser combination, and possibly
a heating apparatus. A Central Air
Conditioner is designed to provide
conditioned air from a central unit to a
whole house with fans and ducts.
The control of the quality, quantity,
and temperature-humidity of the air in
an interior space.
Air Diffuser An air
distribution outlet, typically located
in the ceiling, which mixes conditioned
air with room air.
Measurement A building energy auditing
technique used to determine and/or
locate air leaks in a building shell or
Air Pollution The
presence of contaminants in the air in
concentrations that prevent the normal
dispersive ability of the air, and that
interfere with biological processes and
Air Pollution Control
The use of devices to limit or prevent
the release of pollution into the
Air Quality Standards
The prescribed level of pollutants
allowed in outside or indoor air as
established by legislation.
Air Register The
component of a combustion device that
regulates the amount of air entering the
A material or structural element that
inhibits air flow into and out of a
building's envelope or shell. This is a
continuous sheet composed of
polyethylene, polypropylene, or extruded
polystyrene. The sheet is wrapped around
the outside of a house during
construction to reduce air in-and
exfiltration, yet allow water to easily
diffuse through it.
Air Space The area
between the layers of glazing (panes) of
Cooling and dehumidifying the air in a
building by a refrigeration unit by a
refrigeration unit powered by
electricity or natural gas. This
definition excludes fans, blowers, or
evaporative cooling systems (swamp
coolers) that are not connected to a
Equipment Either a central system,
window or wall units that cool the air
in a housing unit by a refrigeration
unit powered by electricity or natural
gas. This definition excludes fans,
blowers, or evaporative cooling systems
(swamp coolers) that are not connected
to a refrigeration unit.
Airlock Entry A
building architectural element
(vestibule) with two airtight doors that
reduces the amount of air infiltration
and exfiltration when the exterior most
door is opened.
Air-Source Heat Pump
A type of heat pump that transfers
heat from outdoor air to indoor air
during the heating season, and works in
reverse during the cooling season.
Approach (ADA) A building construction
technique used to create a continuous
air retarder that uses the drywall,
gaskets, and caulking. Gaskets are used
rather than caulking to seal the drywall
at the top and bottom. Although it is an
effective energy-saving technique, it
was designed to keep airborne moisture
from damaging insulation and building
materials within the wall cavity.
Air-to-Air Heat Pump
see Air-Source Heat Pump.
Pump A type of heat pump that
transfers heat in outdoor air to water
for space or water heating.
Alaska North Slope (ANS)
A crude oil and natural gas producing
region, located on the northern coastal
plain in Alaska and offshore in the
Albedo The ratio of
light reflected by a surface to the
light falling on it.Alcohol A group of
organic compounds composed of carbon,
hydrogen, and oxygen; a series of
molecules composed of a hydrocarbon plus
a hydroxyl group; includes methanol,
ethanol, isopropyl alcohol and others.
plants, usually aquatic, capable of
synthesizing their own food by
A type of electrical current, the
direction of which is reversed at
regular intervals or cycles; in the U.S.
the standard is 120 reversals or 60
cycles per second; typically abbreviated
Alternative Fuel A
popular term for "nonconventional"
transportation fuels made from natural
gas (propane, compressed natural gas,
methanol, etc.) or biomass materials
Vehicle (AFV) A vehicle designed to
operate on an alternative fuel (e.g.,
compressed natural gas, methane blend,
electricity). The vehicle could be
either a vehicle designed to operate
exclusively on alternative fuel or a
vehicle designed to operate on
alternative fuel and/or a traditional
generator producing alternating current
by the rotation of its rotor, and which
is powered by a primary mover.
Ambient Air The air
external to a building or device.
The temperature of a medium, such as gas
or liquid, which comes into contact with
or surrounds an apparatus or building
colorless, pungent, gas (NH3) that is
extremely soluble in water, may be used
as a refrigerant; a fixed nitrogen form
suitable as fertilizer.
Semiconductor A non-crystalline
semiconductor material that has no
Ampere A unit of
measure for an electrical current; the
amount of current that flows in a
circuit at an electromotive force of one
Volt and at a resistance of one Ohm.
Abbreviated as amp.
Amp-Hours A measure
of the flow of current (in amperes) over
Microorganisms that live in oxygen
A device for optimizing the anaerobic
digestion of biomass and/or animal
manure, and possibly to recover biogas
for energy production. Digester types
include batch, complete mix, continuous
flow (horizontal or plug-flow,
multiple-tank, and vertical tank), and
The complex process by which organic
matter is decomposed by anaerobic
bacteria. The decomposition process
produces a gaseous byproduct often
called "biogas" primarily composed of
methane, carbon dioxide, and hydrogen
Anaerobic Lagoon A
holding pond for livestock manure that
is designed to anaerobically stabilize
manure, and may be designed to capture
biogas, with the use of an impermeable,
For electric power, includes the
provision of reactive power, frequency
control, and load following.
instrument for measuring the force or
velocity of wind; a wind gauge.
Angle of Incidence
In reference to solar energy systems,
the angle at which direct sunlight
strikes a surface; the angle between the
direction of the sun and the
perpendicular to the surface. Sunlight
with an incident angle of 90 degrees
tends to be absorbed, while lower angles
tend to be reflected.
Angstrom Unit A
unit of length named for A.J. Angstome,
a Swedish spectroscopist, used in
measuring electromagnetic radiation
equal to 0.000,000,01 centimeters.
One hundred percent alcohol; neat
Utilization Efficiency (AFUE) The
measure of seasonal or annual efficiency
of a residential heating furnace or
boiler. It takes into account the cyclic
on/off operation and associated energy
losses of the heating unit as it
responds to changes in the load, which
in turn is affected by changes in
weather and occupant controls.
Annual Load Fraction
That fraction of annual energy demand
supplied by a solar system.
Annual Solar Savings
The annual solar savings of a solar
building is the energy savings
attributable to a solar feature relative
to the energy requirements of a
Anode The positive
pole or electrode of an electrolytic
cell, vacuum tube, etc. (see also
Anthracite (coal) A
hard, dense type of coal, that is hard
to break, clean to handle, difficult to
ignite, and that burns with an intense
flame and with the virtual absence of
smoke because it contains a high
percentage of fixed carbon and a low
percentage of volatile matter.
or generated by a human or caused by
human activity. The term is used in the
context of global climate change to
refer to gaseous emissions that are the
result of human activities, as well as
other potentially climatealtering
activities, such as deforestation.
A fluid, such as methanol or ethylene
glycol, added to vehicle engine coolant,
or used in solar heating system heat
transfer fluids, to protect the systems
Coating A thin coating of a material
applied to a photovoltaic cell surface
that reduces the light reflection and
increases light transmission.
opening; in solar collectors, the area
through which solar radiation is
admitted and directed to the absorber.
Apparent Day A
solar day; an interval between
successive transits of the sun's center
across an observer's meridian; the time
thus measured is not equal to clock
Apparent Power (kVA)
This is the voltage-ampere requirement
of a device designed to convert electric
energy to a non-electrical form.
Appliance A piece
of equipment, commonly powered by
electricity, used to perform a
particular energydriven function.
Examples of common appliances are
refrigerators, clothes washers and
dishwashers, conventional ranges/ovens
and microwave ovens, humidifiers and
dehumidifiers, toasters, radios, and
Efficiency Ratings The ratings under
which specified appliances convert
energy sources into useful energy, as
determined by procedures established by
the U.S. Department of Energy.
Standards established by the U.S.
Congress for energy consuming appliances
in the National Appliance Energy
Conservation Act (NAECA) of 1987, and as
amended in the National Appliance Energy
Conservation Amendments of 1988, and the
Energy Policy Act of 1992 (EPAct). NAECA
established minimum standards of energy
efficiency for refrigerators,
refrigerator-freezers, freezers, room
air conditioners, fluorescent lamp
ballasts, incandescent reflector lamps,
clothes dryers, clothes washers,
dishwashers, kitchen ranges and ovens,
pool heaters, television sets (withdrawn
in 1995), and water heaters. The EPAct
added standards for some fluorescent and
incandescent reflector lamps, plumbing
products, electric motors, and
commercial water heaters and Heating,
Ventilation, and Air Conditioning (HVAC)
systems. It also allowed for the future
development of standards for many other
products. The U.S. Department of Energy
(DOE) is responsible establishing the
standards and the procedures that
manufacturers must use to test their
models. These procedures are published
in the Code of Federal Regulations (10
CFR, Ch. II, Part 430), January 1, 1994
Wildlife refuge (ANWR) A National
Wildlife Refuge located adjacent to the
ANS producing region, thought to contain
large crude oil reserves.
Argon A colorless,
odorless inert gas sometimes used in the
spaces between the panes in energy
efficient windows. This gas is used
because it will transfer less heat than
air. Therefore, it provides additional
protection against conduction and
convection of heat over conventional
double -pane windows.
Array (Solar) Any
number of solar photovoltaic modules or
solar thermal collectors or reflectors
connected together to provide electrical
or thermal energy.
non-combustible residue of a combusted
substance composed primarily of alkali
and metal oxides.
for the American Society of Heating,
Refrigeration, and Air-Conditioning
for the American Society for Testing and
Materials, which is responsible for the
issue of many standard methods used in
the energy industry.
Generator A type of electric generator
that produces alternating current that
matches an existing power source.
The pressure of the air at sea level;
one standard atmosphere at zero degrees
centigrade is equal to 14.695 pounds per
square inch (1.033 kilograms per square
The conceptualized concept of an atom,
regarded as consisting of a central
positively charged nucleus (protons and
neutrons) and a number of negatively
charged electrons revolving about in
Atrium An interior
court to which rooms open.
Attic The usually
unfinished space above a ceiling and
below a roof.
Attic Fan A fan
mounted on an attic wall used to exhaust
warm attic air to the outside.
Attic Vent A
passive or mechanical device used to
ventilate an attic space, primarily to
reduce heat buildup and moisture
Audit (Energy) The
process of determining energy
consumption, by various techniques, of a
building or facility.
Automatic (or Remote)
Meter Reading System A system that
records the consumption of electricity,
gas, water, etc, and sends the data to a
central data accumulation device.
Automatic Damper A
device that cuts off the flow of hot or
cold air to or from a room as controlled
by a thermostat.
Auxiliary Energy or
System Energy required to operate
mechanical components of an energy
system, or a source of energy or energy
supply system to back-up another.
Describes the reliability of power
plants. It refers to the number of hours
that a power plant is available to
produce power divided by the total hours
in a set time period, usually a year.
Available Heat The
amount of heat energy that may be
converted into useful energy from a
Average The simple
arithmetic average for a population;
that is, the sum of all the values in a
population divided by the size of the
population. Population means are
estimated by computing the weighted sum
of the sample values, then dividing by
the sum of the sample weights.
Average Cost The
revenue requirement of a utility divided
by the utilitys sales. Average cost
typically includes the costs of existing
power plants, transmission, and
distribution lines, and other facilities
used by a utility to serve its
customers. It also includes operating
and maintenance, tax and fuel expenses.
Average Demand The
demand on, or the power output of, an
electrical system or any of its parts
over an interval of time, as determined
by the total number of kilowatt-hours
divided by the units of time in the
Average Megawatt (aMW)
Equivalent to the energy produced by the
continuous operation of one megawatt of
capacity over a period of one year
(8,760 megawatt hours).
Average Wind Speed
(or Velocity) The mean wind speed over
a specified period of time.
Avoided Cost The
incremental cost to an electric power
producer to generate or purchase a unit
of electricity or capacity or both.
abbreviation for American Wire Gauge;
the standard for gauging the size of
wires (electrical conductors).
architectural element for shading
windows and wall surfaces placed on the
exterior of a building; can be fixed or
Axial Fans Fans in
which the direction of the flow of the
air from inlet to outlet remains
unchanged; includes propeller, tubaxial,
and vaneaxial type fans.
Axial Flow Compressor
A type of air compressor in which air
is compressed in a series of stages as
it flows axially through a decreasing
Axial Flow Turbine
A turbine in which the flow of a steam
or gas is essentially parallel to the
Azimuth (Solar) The
angle between true south and the point
on the horizon directly below the sun.
flow of air down a flue/chimney and into
a house caused by low indoor air
pressure that can occur when using
several fans or fireplaces and/or if the
house is very tight.
Backup Energy System
A reserve appliance; for example, a
stand-by generator for a home or
Single-celled organisms, free-living or
parasitic, that break down the wastes
and bodies of dead organisms, making
their components available for reuse by
Baffle A device,
such as a steel plate, used to check,
retard, or divert a flow of a material.
Bagasse The fibrous
material remaining after the extraction
of juice from sugarcane; often burned by
sugar mills as a source of energy.
Baghouse An air
pollution control device used to filter
particulates from waste combustion
gases; a chamber containing a bag
Balance Point An
outdoor temperature, usually 20 to 45
degrees Fahrenheit, at which a heat
pump's output equals the heating demand.
Below the balance point, supplementary
heat is needed.
In a renewable energy system, refers to
all components other than the mechanism
used to harvest the resource (such as
photovoltaic panels or a wind turbine).
Balance-of-system costs can include
design, land, site preparation, system
installation, support structures, power
conditioning, operation and maintenance,
Baling A means of
reducing the volume of a material by
compaction into a bale.
Ballast A device
used to control the voltage in a
Factor The measure of the efficiency
of fluorescent lamp ballasts. It is the
relative light output divided by the
Ballast Factor The
ratio of light output of a fluorescent
lamp operated on a ballast to the light
output of a lamp operated on a standard
or reference ballast.
Band Gap In a
semiconductor, the energy difference
between the highest valence band and the
lowest conduction band.
Band Gap Energy The
amount of energy (in electron volts)
required to free an outer shell electron
from its orbit about the nucleus to a
free state, and thus promote it from the
valence to the conduction level.
Barrel (petroleum) A
unit of volume equal to 42 U.S. gallons.
One barrel weights 306 pounds or 5.80
million Btu of crude oil. Barrel is
abbreviated as bbl.
The amount of heat given off by a person
at rest in a comfortable environment;
approximately 50 Btu per hour (Btu/h).
Base Power Power
generated by a power generator that
operates at a very high capacity factor.
A type of radiant heating system where
the radiator is located along an
exterior wall where the wall meets the
The power output of a power plant that
can be continuously produced.
Baseload Demand The
minimum demand experienced by a power
Baseload Power Plant
A power plant that is normally
operated to generate a base load, and
that usually operates at a constant
load; examples include coal fired and
nuclear fueled power plants.
conditioned or unconditioned space below
the main living area or primary floor of
Batch Heater This
simple passive solar hot water system
consists of one or more storage tanks
placed in an insulated box that has a
glazed side facing the sun. A batch
heater is mounted on the ground or on
the roof (make sure your roof structure
is strong enough to support it). Some
batch heaters use "selective" surfaces
on the tank(s). These surfaces absorb
sun well but inhibit radiative loss.
Also known as bread box systems or
integral collector storage systems.
Batch Process A
process for carrying out a reaction in
which the reactants are fed in discrete
and successive charges.
flexible roll or strip of insulating
material in widths suited to standard
spacings of building structural members
(studs and joists). They are made from
glass or rock wool fibers. Blankets are
continuous rolls. Batts are pre-cut to
four or eight foot lengths.
Battery An energy
storage device composed of one or more
Storage Energy storage using
electrochemical batteries. The three
main applications for battery energy
storage systems include spinning reserve
at generating stations, load leveling at
substations, and peak shaving on the
customer side of the meter.
Bcf One billion
cubic feet of gas.
Beadwall A form
of movable insulation that uses tiny
polystyrene beads blown into the space
between two window panes.
Solar radiation that is not scattered by
dust or water droplets.
Bearing Wall A wall
that carries ceiling rafters or roof
Benefits Charge -The
addition of a per unit tax on sales of
electricity, with the revenue generated
used for or to encourage investments in
energy efficiency measures and/or
renewable energy projects.
Bimetal Two metals
of different coefficients of expansion
welded together so that the piece will
bend in one direction when heated, and
in the other when cooled, and can be
used to open or close electrical
circuits, as in thermostats.
Bin Method A method
of predicting heating and/or cooling
loads using instantaneous load
calculation at different outdoor
dry-bulb temperatures, and multiplying
the result by the number of hours of
occurrence of each temperature.
Combination of two power plant turbine
cycles utilizing two different working
fluids for power production. The waste
heat from the first turbine cycle
provides the heat energy for the
operation of the second turbine, thus
providing higher overall system
Geothermal Plants Binary cycle systems
can be used with liquids at temperatures
less than 350 F (177 C). In these
systems, the hot geothermal liquid
vaporizes a secondary working fluid,
which then drives a turbine.
Demand The weight of oxygen taken up
mainly as a result of the oxidation of
the constituents of a sample of water by
biological action; expressed as the
number of parts per million of oxygen
taken up by the sample from water
originally saturated with air, usually
over a period of five days at 20 degrees
centigrade. A standard means of
estimating the degree of contamination
conversion of one form of energy into
another by the action of plants or
microorganisms. The conversion of
biomass to ethanol, methanol, or
alternative fuel that can be made from
any fat or vegetable oil. It can be used
in any diesel engine with few or no
modifications. Although biodiesel does
not contain petroleum, it can be blended
with diesel at any level or used in its
conversion of the complex carbohydrates
in organic material into energy.
fuels and blending components produced
from biomass (plant) feedstocks, used
primarily for transportation.
combustible gas created by anaerobic
decomposition of organic material,
composed primarily of methane, carbon
dioxide, and hydrogen sulfide.
biomethanization The process of
decomposing biomass with anaerobic
bacteria to produce biogas.
Biomass Any organic
(plant or animal) material which is
available on a renewable basis,
including agricultural crops and
agricultural wastes and residues, wood
and wood wastes and residues, animal
wastes, municipal wastes, and aquatic
plants. The total biological matter, or
stored energy content of living or dead
organisms, existing in a given specified
volume or area.
Energy produced by the conversion of
biomass directly to heat or to a liquid
or gas that can be converted to energy.
Biomass converted directly to energy or
converted to liquid or gaseous fuels
such as ethanol, methanol, methane, and
The conversion of biomass into a gas,
by biogasification (see above) or
thermal gasification, in which hydrogen
is produced from high-temperature
gasifying and low-temperature pyrolysis
action of light on a biological system
that results in the dissociation of a
substrate, usually water, to produce
landfill where the waste actively
decomposes rather being simply buried in
a "dry tomb."
Blackbody An ideal
substance that absorbs all radiation
falling on it, and reflecting nothing.
Blower The device
in an air conditioner that distributes
the filtered air from the return duct
over the cooling coil/heat exchanger.
This circulated air is cooled/heated and
then sent through the supply duct, past
dampers, and through supply diffusers to
the living/working space.
Blower Door A
device used by energy auditors to
pressurize a building to locate places
of air leakage and energy loss.
Blown In Insulation
(see also Loose Fill) An insulation
product composed of loose fibers or
fiber pellets that are blown into
building cavities or attics using
special pneumatic equipment.
Boiler a tank in
which water is heated to produce either
hot water or steam that is circulated
for the purpose of heating and power.
The water that is forced into a boiler
to take the place of that which is
evaporated in the generation of steam.
Boiler Horsepower A
unit of rate of water evaporation equal
to the evaporation per hour of 34.5
pounds of water at a temperature of 212
degrees Fahrenheit into steam at 212
Boiler Pressure The
pressure of the steam or water in a
boiler as measured; usually expressed in
pounds per square inch gauge (psig).
Boiler Rating The
heating capacity of a steam boiler;
expressed in Btu per hour (Btu/h), or
horsepower, or pounds of steam per hour.
Boiling Water Reactor
A nuclear reactor in which water is
allowed to boil in the core. The
resulting steam is used to drive a
turbine generating electric power.
Bone (Oven) Dry In
reference to solid biomass fuels, such
as wood, having zero moisture content.
Bone Dry Unit A
quantity of (solid) biomass fuel equal
to 2,400 pounds bone dry.
Booster Pump A pump
for circulating the heat transfer fluid
in a hydronic heating system.
Boot In heating and
cooling system distribution ductwork,
the transformation pieces connecting
horizontal round leaders to vertical
Boron The chemical
element commonly used as the dopant in
solar photovoltaic device or cell
Bottled Gas A
generic term for liquefied and
pressurized gas, ordinarily butane,
propane, or a mixture of the two,
contained in a cylinder for domestic
means to increase the thermal efficiency
of a steam electric generating system by
converting some waste heat from the
condenser into electricity. The heat
engine in a bottoming cycle would be a
condensing turbine similar in principle
to a steam turbine but operating with a
different working fluid at a much lower
temperature and pressure.
Brayton Cycle A
thermodynamic cycle using constant
pressure, heat addition and rejection,
representing the idealized behavior of
the working fluid in a gas turbine type
Bread Box System
This simple passive solar hot water
system consists of one or more storage
tanks placed in an insulated box that
has a glazed side facing the sun. A
bread box system is mounted on the
ground or on the roof (make sure your
roof structure is strong enough to
support it). Some systems use
"selective" surfaces on the tank(s).
These surfaces absorb sun well but
inhibit radiative loss. Also known as
batch heaters or integral collector
saturated or strongly impregnated with
British Thermal Unit
(Btu) The amount of heat required to
raise the temperature of one pound of
water one degree Fahrenheit; equal to
252 calories. British thermal unit is
abbreviated as Btu.
Btu British thermal
unit of energy The amount of energy
needed to heat one pound of water one
Building Energy Ratio
The space-conditioning load of a
The structural elements (walls, roof,
floor, foundation) of a building that
encloses conditioned space; the building
Factor A measure of the heating
requirements of a building expressed in
Btu per degree-day.
The relationship of a building to true
south, as specified by the direction of
its longest axis.
Energy Loss Coefficient-Area Product
The factor, when multiplied by the
monthly degree-days, that yields the
monthly space heating load.
Building Overall Heat
Loss Rate The overall rate of heat
loss from a building by means of
transmission plus infiltration,
expressed in Btu per hour, per degree
temperature difference between the
inside and outside.
transparent or opaque sphere in an
electric light that the electric light
Bulb Turbine A type
of hydro turbine in which the entire
generator is mounted inside the water
passageway as an integral unit with the
turbine. These installations can offer
significant reductions in the size of
Bulk Density The
weight of a material per unit of volume
compared to the weight of the same
volume of water.
Burner Capacity The
maximum heat output (in Btu per hour)
released by a burner with a stable flame
and satisfactory combustion.
Burning Point The
temperature at which a material ignites.
Bus (electrical) An
electrical conductor that serves as a
common connection for two or more
electrical circuits; may be in the form
of rigid bars or stranded conductors or
Busbar The power
conduit of an electric power plant; the
starting point of the electric
Busbar Cost The
cost of producing electricity up to the
point of the power plant busbar.
alternative path. In a heating duct or
pipe, an alternative path for the flow
of the heat transfer fluid from one
point to another, as determined by the
opening or closing of control valves
both in the primary line and the bypass
average fuel efficiency (federal law)
Cage The component
of an electric motor composed of solid
bars (of usually copper or aluminum)
arranged in a circle and connected to
continuous rings at each end. This cage
fits inside the stator in an induction
motor in channels between laminations,
thin flat discs of steel in a ring
Calorie A unit for
measuring heat energy. This unit is
equal to 4.184 joules. Often used
instead of joules when dealing with the
energy released from food. The amount of
heat required to raise the temperature
of a unit of water, at or near the
temperature of maximum density, one
degree Celsius (or Centigrade [C]);
expressed as a "small calorie" (the
amount of heat required to raise the
temperature of 1 gram of water one
degree C), or as a "large calorie" or
"kilogram calorie" (the amount of heat
required to raise one kilogram [1,000
grams] of water one degree C);
capitalization of the word calorie
indicates a kilogram-calorie.
Calorific Value The
heat liberated by the combustion of a
unit quantity of a fuel under specific
conditions; measured in calories.
luminous intensity, in a given
direction, of a source that emits
monochromatic radiation of frequency 540
Χ 1012 hertz and that has a radiant
intensity in that direction of 1/683
watt per steradian.
Candle Power The
illuminating power of a standard candle
employed as a unit for determining the
illuminating quality of an illuminant.
maximum load that a generating unit,
power plant, or other electrical
apparatus can carry under specified
conditions for a given period of time,
without exceeding its approved limits of
temperature and stress.
The difference between net electrical
system capability and system maximum
load requirements (peak load); the
margin of capability available to
provide for scheduled maintenance,
emergency outages, system operating
requirements and unforeseen loads.
measure of the electrical charge of a
capacitor consisting of two plates
separated by an insulating material.
electrical device that adjusts the
leading current of an applied
alternating current to balance the lag
of the circuit to provide a high power
maximum power that a machine or system
can produce or carry under specified
conditions. The capacity of generating
equipment is generally expressed in
kilowatts or megawatts. In terms of
transmission lines, capacity refers to
the maximum load a line is capable of
carrying under specified conditions. The
load that a power generation unit or
other electrical apparatus or heating
unit is rated by the manufacture to be
able to meet or supply.
Unit) The refrigerating effect in
Btu/h produced by the difference in
total enthalpy between a refrigerant
liquid leaving the unit and the total
enthalpy of the refrigerant vapor
entering it. Generally measured in tons
of a motor) The maximum load that a
motor is capable of supplying.
Capacity (Heating, of
a material) The amount of heat energy
needed to raise the temperature of a
given mass of a substance by one degree
Celsius. The heat required to raise the
temperature of 1 kg of water by 1 degree
Celsius is 4186 Joules.
Capacity Factor The
ratio of the average load on (or power
output of) a generating unit or system
to the capacity rating of the unit or
system over a specified period of time.
Capital Costs The
amount of money needed to purchase
equipment, buildings, tools, and other
manufactured goods that can be used in
Any customer that cannot readily
purchase power from suppliers other than
the local utility, even if they have the
legal right to do so. Captive
electricity customers are generally
considered to be the residential and
small commercial customers. The large
commercial and industrial customers, in
contrast, are thought to be more mobile.
This mobility, or lack thereof, relates
to the restructuring debate since the
larger customers can threaten to leave
the area (causing greater rates as fewer
customers share the bill for fixed or
sunk costs) or are able to win greater
concessions in a negotiated process
through their buying power.
Carbon Dioxide A
colorless, odorless noncombustible gas
with the formula CO2 that is present in
the atmosphere. It is formed by the
combustion of carbon and carbon
compounds (such as fossil fuels and
biomass) and by respiration, which is a
slow combustion in animals and plants,
and by the gradual oxidation of organic
matter in the soil.
Carbon Dioxide (C02)
A colorless, odorless noncombustible gas
with the formula C02 that is present in
the atmosphere. It is formed by the
combustion of carbon and carbon
compounds (such as fossil fuels and
biomass), by respiration, which is a
slow combustion in animals and plants,
and by the gradual oxidation of organic
matter in the soil.
C02 A gas that is a
product of combustion. It is one of the
byproducts of burning natural gas and
other fossil fuels. It is considered by
many scientists as a contributor to
Carbon Monoxide A
colorless, odorless but poisonous
combustible gas with the formula CO.
Carbon monoxide is produced in the
incomplete combustion of carbon and
carbon compounds such as fossil fuels
(i.e. coal, petroleum) and their
products (e.g. liquefied petroleum gas,
gasoline), and biomass.
Carbon taxes Taxes
applied to a fuel based on its carbon
content. These taxes are designed to
reflect the environmental impact of the
greenhouse gases produced when the fuel
Carbon Zinc Cell
Battery A cell produces electric
energy by the galvanic oxidation of
carbon; commonly used in household
and Renewable Energy System, a joint
operating agency formed by seven
Washington public utility districts
Carnot Cycle An
ideal heat engine (conceived by Sadi
Carnot) in which the sequence of
operations forming the working cycle
consists of isothermal expansion,
adiabatic expansion, isothermal
compression, and adiabatic compression
back to its initial state.
An air pollution control device that
removes organic contaminants by
oxidizing them into carbon dioxide and
water through a chemical reaction using
a catalysis, which is a substance that
increases (or decreases) the rate of a
chemical reaction without being changed
itself; required in all automobiles sold
in the United State, and used in some
types of heating appliances.
Ceiling/Roof A type of ceiling and
roof assembly that has no attic.
negative pole or electrode of an
electrolytic cell, vacuum tube, etc.,
where electrons enter (current leaves)
the system; the opposite of an anode.
Ballast An electromagnetic ballast
that disconnects a lamp's electrode
heating circuit once is has started;
often called "low frequency electronic"
A method of preventing oxidation of the
exposed metal in structures by imposing
between the structure and the ground a
small electrical voltage.
Caulking A material
used to seal areas of potential air
leakage into or out of a building
downward facing structural element that
is directly opposite the floor.
Ceiling Fan A
mechanical device used for air
circulation and to provide cooling.
Cell A component of
a electrochemical battery. A 'primary'
cell consists of two dissimilar
elements, known as 'electrodes,'
immersed in a liquid or paste known as
the 'electrolyte.' A direct current of
1-1.5 volts will be produced by this
cell. A 'secondary' cell or accumulator
is a similar design but is made useful
by passing a direct current of correct
strength through it in a certain
direction. Each of these cells will
produce 2 volts; a 12 volt car battery
contains six cells.
Cellulase An enzyme
complex, produced by fungi and bacteria,
capable of decomposing cellulose into
small fragments, primarily glucose.
fundamental constituent of all
vegetative tissue; the most abundant
material in the world.
A type of insulation composed of waste
newspaper, cardboard, or other forms of
System A system where heat is supplied
to areas of a building from a single
appliance through a network of ducts or
Central Power Plant
A large power plant that generates power
for distribution to multiple customers.
Solar Power Plants Also known as
"power towers," these use fields of
two-axis tracking mirrors known as
heliostats. Each heliostat is
individually positioned by a computer
control system to reflect the sun's rays
to a tower-mounted thermal receiver. The
effect of many heliostats reflecting to
a common point creates the combined
energy of thousands of suns, which
produces high-temperature thermal
energy. In the receiver, molten nitrate
salts absorb the heat energy. The hot
salt is then used to boil water to
steam, which is sent to a conventional
steam turbine-generator to produce
Cetane Number A
measure of a fuel's (liquid) ease of
Chain Reaction A
selfsustaining nuclear reaction which
takes place during fission. A
fissionable substance (i.e., uranium)
absorbs a neutron and divides, releasing
additional neutrons that are absorbed by
other fissionable nuclei, releasing
still more neutrons.
Char A byproduct of
low-temperature carbonization of a solid
Charcoal A material
formed from the incomplete combustion or
destructive distillation (carbonization)
of organic material in a kiln or retort,
and having a high energy density, being
nearly pure carbon. (If produced from
coal, it is coke.) Used for cooking, the
manufacture of gunpowder and steel
(notably in Brazil), as an absorbent and
decolorizing agent, and in sugar
refining and solvent recovery.
Charge Carrier A
free and mobile conduction electron or
hole in a semiconductor.
An electronic device that regulates the
electrical charge stored in batteries so
that unsafe, overcharge conditions for
the batteries are avoided.
Energy stored in a substance and
released during a chemical reaction such
as burning wood, coal, or oil.
Deposition (CVD) A method of
depositing thin semiconductor films used
to make certain types of solar
photovoltaic devices. With this method,
a substrate is exposed to one or more
vaporized compounds, one or more of
which contain desirable constituents. A
chemical reaction is initiated, at or
near the substrate surface, to produce
the desired material that will condense
on the substrate.
Chiller A device
for removing heat from a gas or liquid
stream for air conditioning/cooling.
Chimney A masonry
or metal stack that creates a draft to
bring air to a fire and to carry the
gaseous byproducts of combustion safely
Chimney Effect The
tendency of heated air or gas to rise in
a duct or other vertical passage, such
as in a chimney, small enclosure, or
building, due to its lower density
compared to the surrounding air or gas.
(CFC) A family of chemicals composed
primarily of carbon, hydrogen, chlorine,
and fluorine whose principal
applications are as refrigerants and
industrial cleansers and whose principal
drawback is the tendency to destroy the
Earth's protective ozone layer.
Circuit A device,
or system of devices, that allows
electrical current to flow through it
and allows voltage to occur across
positive and negative terminals.
Circuit Breaker A
device used to interrupt or break an
electrical circuit when an overload
condition exists; usually installed in
the positive circuit; used to protect
Circuit Lag As time
increases from zero at the terminals of
an inductor, the voltage comes to a
particular value on the sine function
curve ahead of the current. The voltage
reaches its negative peak exactly 90
degrees before the current reaches its
negative peak thus the current lags
behind by 90 degrees.
conductor or a system of conductors
through which electric current flows.
Bed A type of furnace or reactor in
which the emission of sulfur compounds
is lowered by the addition of crushed
limestone in the fluidized bed thus
obviating the need for much of the
expensive stack gas clean-up equipment.
The particles are collected and
recirculated, after passing through a
conventional bed, and cooled by boiler
Clean Power Generator
A company or other organizational unit
that produces electricity from sources
that are thought to be environmentally
cleaner than traditional sources. Clean,
or green, power is usually defined as
power from renewable energy that comes
from wind, solar, biomass energy, etc.
There are various definitions of clean
resources. Some definitions include
power produced from waste-to-energy and
wood-fired plants that may still produce
significant air emissions. Some states
have defined certain local resources as
clean that other states would not
consider clean. For example, the state
of Texas has defined power from
efficient natural gas-fired power plants
as clean. Some northwest states include
power from large hydropower projects as
clean although these projects damage
fish populations. Various states have
disclosure and labeling requirement for
generation source and air emissions that
assist customers in comparing
electricity characteristics other than
price. This allows customers to decide
for themselves what they consider to be
"clean." The federal government is also
exploring this issue.
Cleavage of Lateral
Epitaxial Films for Transfer (CLEFT) A
process for making inexpensive Gallium
Arsenide (GaAs) photovoltaic cells in
which a thin film of GaAs is grown atop
a thick, single-crystal GaAs (or other
suitable material) substrate and then is
cleaved from the substrate and
incorporated into a cell, allowing the
substrate to be reused to grow more
Clerestory A window
located high in a wall near the eaves
that allows daylight into a building
interior, and may be used for
ventilation and solar heat gain.
prevailing or average weather conditions
of a geographic region.
Climate Change A
term used to refer to all forms of
climatic inconsistency, but especially
to significant change from one
prevailing climatic condition to
another. Used to describe short and
long-term affects on the Earth's climate
as a result of human activities such as
fossil fuel combustion and vegetation
clearing and burning. In some cases,
"climate change" has been used
synonymously with the term "global
warming"; scientists, however, tend to
use the term in a wider sense inclusive
of natural changes in climate, including
Close Coupled An
energy system in which the fuel
production equipment is in close
proximity, or connected to, the fuel
Closed Cycle A
system in which a working fluid is used
over and over without introduction of
new fluid, as in a hydronic heating
system or mechanical refrigeration
As defined by the Comprehensive National
Energy Act of 1992 (or the Energy Policy
Act; EPAct): any organic matter from a
plant which is planted for the exclusive
purpose of being used to produce
energy." This does not include wood or
agricultural wastes or standing timber.
Geothermal Heat Pump Systems
Closed-loop (also known as "indirect")
systems circulate a solution of water
and antifreeze through a series of
sealed loops of piping. Once the heat
has been transferred into or out of the
solution, the solution is recirculated.
The loops can be installed in the ground
horizontally or vertically, or they can
be placed in a body of water, such as a
pond. See horizontal ground loop,
vertical ground loop, slinky ground
loop, and surface water loop for more
information on the different types of
closed-loop geothermal heat pump
Coal A fossil fuel
formed by the breakdown of vegetable
material trapped underground without
access to air.
Plant A power plant that uses coal as
the fuel to generate electricity.
documents that regulate construction to
protect the health, safety, and welfare
of people. Codes establish minimum
standards but do not guarantee
efficiency or quality.
Coefficient of Heat
Transmission (U-Value) A value that
describes the ability of a material to
conduct heat. The number of Btu that
flow through 1 square foot of material,
in one hour. It is the reciprocal of the
R-Value (U-Value = 1/R-Value).
Performance (COP) A ratio of the work
or useful energy output of a system
versus the amount of work or energy
inputted into the system as determined
by using the same energy equivalents for
energy in and out. Is used as a measure
of the steady state performance or
energy efficiency of heating, cooling,
and refrigeration appliances. The COP is
equal to the Energy Efficiency Ratio (EER)
divided by 3.412. The higher the COP,
the more efficient the device.
Utilization (CU) A term used for
lighting appliances; the ratio of lumens
received on a flat surface to the light
output, in lumens, from a lamp; used to
evaluate the effectiveness of luminaries
in delivering light.
process of burning natural gas in
conjunction with another fuel to reduce
air pollutants. Cofiring The use of
two or more different fuels (e.g. wood
and coal) simultaneously in the same
combustion chamber of a power plant.
the heat incidentally generated by one
process to accomplish another task. For
example, in a gasfired electricity
generating plant, the heat not converted
to electricity could be used as steam
for food processing.
Cogenerator A class
of energy producer that produces both
heat and electricity from a single fuel.
Coil As a component
of a heating or cooling appliance, rows
of tubing or pipe with fins attached
through which a heat transfer fluid is
circulated and to deliver heat or
cooling energy to a building.
The ratio of the coincident, maximum
demand or two or more loads to the sum
of their noncoincident maximum demand
for a given period; the reciprocal of
the diversity factor, and is always less
than or equal to one.
The demand of a consumer of electricity
at the time of a power supplier's peak
Cold Night Sky The
low effective temperature of the sky on
a clear night.
component of a solar energy heating
system that collects solar radiation,
and that contains components to absorb
solar radiation and transfer the heat to
a heat transfer fluid (air or liquid).
The ratio of solar radiation captured
and transferred to the collector (heat
Collector Field The
area where many solar collectors are
situated in a solar power plant.
Collector Fluid The
fluid, liquid (water or water/antifreeze
solution) or air, used to absorb solar
energy and transfer it for direct use,
indirect heating of interior air or
domestic water, and/or to a heat storage
Collector Tilt The
angle that a solar collector is
positioned from horizontal.
Color Rendering or
Rendition A measure of the ability of
a light source to show colors, based on
a color rendering index.
(Rendering) Index (CRI) A measure of
light quality. The maximum CRI value of
100 is given to natural daylight and
incandescent lighting. The closer a
lamp's CRI rating is to 100, the better
its ability to show true colors to the
Color Temperature A
measure of the quality of a light source
by expressing the color appearance
correlated with a black body.
Plant A power plant that uses two
thermodynamic cycles to achieve higher
overall system efficiency; e.g.: the
heat from a gas-fired combustion turbine
is used to generate steam for heating or
to operate a steam turbine to generate
oxidation accompanied by the generation
of light and heat. The process of
burning; the oxidation of a material by
applying heat, which unites oxygen with
a material or fuel.
Combustion Air Air
that provides the necessary oxygen for
complete, clean combustion and maximum
Any wholly or partially enclosed space
in which combustion takes place.
The gaseous byproducts of the combustion
of a fuel.
Plant A power plant that generates
power by combusting a fuel.
A turbine that generates power from the
combustion of a fuel.
Comfort Zone A
frequently used room or area that is
maintained at a more comfortable level
than the rest of the house; also known
as a "warm room."
A building with more than 50 percent of
its floor space used for commercial
activities, which include stores,
offices, schools, churches, libraries,
museums, health care facilities,
warehouses, and government buildings
except those on military bases.
Consists of businesses that are not
engaged in transportation or
manufacturing or other types of
industrial activities. Standard
Industrial Classification (SIC) codes
for commercial establishments are 50
through 87, 89, and 91 through 97.
Commercial Sector (of
Economy) The part of the economy
having to do with the buying and selling
of goods and services. The commercial
sector is made up of merchants,
process by which a power plant,
apparatus, or building is approved for
operation based on observed or measured
operation that meets design
Regional Electric Power Cooperation (CREPC)
Created by the Western Interstate
Energy Board, in conjunction with the
Western Conference of Public Service
Commissioners, consists of the public
utility commissions, energy agencies,
and facility siting agencies in the
western states and Canadian provinces in
the western electricity grid. CREPC
works to improve the efficiency of the
western electric power system.
A smaller version of standard
fluorescent lamps which can directly
replace standard incandescent lights.
These lights consist of a gas filled
tube, and a magnetic or electronic
Tariffs In a restructured wholesale
electrical market, according to FERc
Order 888, there should be
nondiscriminatory, open access charges
or tariffs for use of the transmission
network by all generators of wholesale
electricity on a comparable basis. These
tariffs provide that the same prices,
terms and conditions would apply to both
the utility for its own transactions and
to other generators.
Complete Mix Digester
A type of anaerobic digester that has
a mechanical mixing system and where
temperature and volume are controlled to
maximize the anaerobic digestion process
for biological waste treatment, methane
production, and odor control.
process of degrading organic material
(biomass) by microorganisms in aerobic
Composting Toilet A
self-contained toilet that use the
process of aerobic decomposition
(composting) to break down feces into
humus and odorless gases.
Collector A form of solar
concentrating collector that does not
track the sun.
Storage The storage of compressed air
in a container for use to operate a
prime mover for electricity generation.
Gas (CNG) Natural gas (methane) that
has been compressed to a higher pressure
gaseous state by a compressor. Natural
gas is compressed into tanks. It is
often used to power natural gas
A cooling device that uses mechanical
energy to produce chilled water.
Compressor A device
used to compress air for mechanical or
electrical power production, and in air
conditioners, heat pumps, and
refrigerators to pressurize the
refrigerant and enabling it to flow
through the system.
Collector A solar collector that uses
reflective surfaces to concentrate
sunlight onto a small area, where it is
absorbed and converted to heat or, in
the case of solar photovoltaic (PV)
devices, into electricity. Concentrators
can increase the power flux of sunlight
hundreds of times. The principal types
of concentrating collectors include:
compound parabolic, parabolic trough,
fixed reflector moving receiver, fixed
receiver moving reflector, Fresnel lense,
and central receiver. A PV concentrating
module uses optical elements (Fresnel
lense) to increase the amount of
sunlight incident onto a PV cell.
Concentrating PV modules/arrays must
track the sun and use only the direct
sunlight because the diffuse portion
cannot be focused onto the PV cells.
Concentrating collectors for home or
small business solar water heating
applications are usually parabolic
troughs that concentrate the sun's
energy on an absorber tube (called a
receiver), which contains a
liquid resulting when water vapor
contacts a cool surface; also the liquid
resulting when a vaporized working fluid
(such as a refrigerant) is cooled or
process by which water in air changes
from a vapor to a liquid due to a change
in temperature or pressure; occurs when
water vapor reaches its dew point
(condensation point); also used to
express the existence of liquid water on
device in an air conditioner or heat
pump in which the refrigerant condenses
from a gas to a liquid when it is
depressurized or cooled.
Condenser Coil The
device in an air conditioner or heat
pump through which the refrigerant is
circulated and releases heat to the
surroundings when a fan blows outside
air over the coils. This will return the
hot vapor that entered the coil into a
hot liquid upon exiting the coil.
A type of heating appliance that
extracts so much of the available heat
content from a combusted fuel that the
moisture in the combustion gases
condenses before it leaves the furnace.
Also this furnace circulates a liquid to
cool the furnace's heat exchanger. The
heated liquid may either circulate
through a liquid-to-air heat exchanger
to warm room air, or it may circulate
through a coil inside a separate
indirect-fired water heater.
Condensing Unit The
component of a central air conditioner
that is designed to remove heat absorbed
by the refrigerant and transfer it
outside the conditioned space.
The interior space of a building that is
heated or cooled.
transfer of heat through a material by
the transfer of kinetic energy from
particle to particle; the flow of heat
between two materials of different
temperatures that are in direct physical
Conduction Band An
energy band in a semiconductor in which
electrons can move freely in a solid,
producing a net transport of charge.
(Thermal) This is a positive constant,
k, that is a property of a substance and
is used in the calculation of heat
transfer rates for materials. It is the
amount of heat that flows through a
specified area and thickness of a
material over a specified period of time
when there is a temperature difference
of one degree between the surfaces of
material through which electricity is
transmitted, such as an electrical wire,
or transmission or distribution line.
Conduit A tubular
material used to encase and protect one
or more electrical conductors.
Connected Load The
sum of the ratings of the electricity
consuming apparatus connected to a
An amount paid by a customer for being
connected to an electricity supplier's
transmission and distribution system.
reduce or avoid the consumption of a
resource or commodity.
Adjustment A means of billing electric
power consumers to pay for the costs of
demand side management/energy
conservation measures and programs. (See
also Benefits Charge.)
The value or purchasing power of a
dollar in a specified year carried
forward or backward.
Turbines Wind turbines that operate at
a constant rotor revolutions per minute
(RPM) and are optimized for energy
capture at a given rotor diameter at a
particular speed in the wind power
The part of a power provider's charge
based on actual energy consumed by the
customer; the product of the
kilowatt-hour rate and the total
The resistance between metallic contacts
and the semiconductor.
Fermentation A steady-state
difference between the brightness of an
object compared to that of its immediate
transfer of heat by means of air
The fossil fuels: coal, oil, and natural
Pump This type of heat pump is known
as an air-to air system.
Power generation from sources such as
petroleum, natural gas, or coal. In some
cases, large-scale hydropower and
nuclear power generation are considered
The amount of energy produced as a
percentage of the amount of energy
A number that translates units of one
measurement system into corresponding
values of another measurement system.
Converter A device
for transforming the quality and
quantity of electrical energy; also an
The quantity of heat that a cooling
appliance is capable of removing from a
room in one hour.
Cooling Degree Day
A value used to estimate interior air
cooling requirements (load) calculated
as the number of degrees per day (over a
specified period) that the daily average
temperature is above 65 degrees
Fahrenheit (or some other, specified
base temperature). The daily average
temperature is the mean of the maximum
and minimum temperatures recorded for a
specific location for a 24 hour period.
Cooling Load That
amount of cooling energy to be supplied
(or heat and humidity removed) based on
the sensible and latent loads.
Cooling Pond A body
of water used to cool the water that is
circulated in an electric power plant.
Cooling Tower A
structure used to cool power plant
water; water is pumped to the top of the
tubular tower and sprayed out into the
center, and is cooled by evaporation as
it falls, and then is either recycled
within the plant or is discharged.
potentially useful byproducts of ethanol
Cord (of Wood) A
stack of wood 4 feet by 4 feet by 8
Coulomb A unit for
the quantity of electricity transported
in 1 second by a current of 1 ampere.
Exchanger A heat exchanger in which
two fluids flow in opposite directions
for transfer heat energy from one to the
Restrictions on the use of a property.
unoccupied, and usually unfinished and
unconditioned space between the floor,
foundation walls, and the slab or ground
of a building.
Creosote A liquid
byproduct of wood combustion (or
distillation) that condenses on the
internal surfaces of vents and chimneys,
which if not removed regularly, can
corrode the surfaces and fuel a chimney
Pressure The highest possible pressure
in a fuel-air mixture before spontaneous
Crude Oil (including
lease condensate) A mixture of
hydrocarbons that exists in liquid phase
in underground reservoirs and remains
liquid at atmospheric pressure after
passing through surface separating
(refining) facilities. Included are
lease condensate and liquid hydrocarbons
produced from tar sands, gilsonite, and
Photovoltaic Cell A type of
photovoltaic cell made from a single
crystal or a polycrystalline slice of
silicon. Crystalline silicon cells can
be joined together to form a module (or
CTED Department of
Community, Trade, and Economic
Cube Law In
reference to wind energy, for any given
instant, the power available in the wind
is proportional to the cube of the wind
velocity; when wind speed doubles, the
power availability increases eight
Cubic Foot (of
Natural Gas) A unit of volume equal to
1 cubic foot at a pressure base of 14.73
pounds standard per square inch absolute
and a temperature base of 60 degrees
Cubic Foot of Natural
Gas Approximately 1,000 Btus.
The flow of electrical energy
(electricity) in a conductor, measured
Current Dollars The
value or purchasing power of a dollar
that has not been reduced to a common
basis of constant purchasing power, but
instead reflects anticipated future
inflation; when used in computations the
assumed inflation rate must be stated.
Customer Charge An
amount to be paid for energy
periodically by a customer without
regard to demand or energy consumption.
Categories of energy consumers, as
defined by consumption or demand levels,
patterns, and conditions, and generally
included residential, commercial,
lowest wind speed at which a wind
turbine begins producing usable power.
highest wind speed at which a wind
turbine stops producing power.
alternating current, the current goes
from zero potential or voltage to a
maximum in one direction, back to zero,
and then to a maximum potential or
voltage in the other direction. The
number of complete cycles per second
determines the current frequency; in the
U.S. the standard for alternating
current is 60 cycles.
Cycling Losses The
loss of heat as the water circulates
through a water heater tank and inlet
and outlet pipes.
Cyclone Burner - A
furnace/combustion chamber in which
finely ground fuel is blown in spirals
in the combustion chamber to maximize
A method of growing large size, high
quality semiconductor crystal by slowly
lifting a seed crystal from a molten
bath of the material under careful
Dam A structure for
impeding and controlling the flow of
water in a water course, and which
increases the water elevation to create
the hydraulic head. The reservoir
creates, in effect, stored energy.
Damper A movable
plate used to control air flow; in a
wood stove or fireplace, used to control
the amount and direction of air going to
Machine A type of vertical-axis wind
machine that has long, thin blades in
the shape of loops connected to the top
and bottom of the axle; often called an
Daylighting The use
of direct, diffuse, or reflected
sunlight to provide supplemental
lighting for building interiors.
(Energy) System Energy systems supply
individual, or small-groups, of energy
angular position of the sun at solar
noon with respect to the plane of the
Declining Block Rate
An electricity supplier rate structure
in which the per unit price of
electricity decreases as the amount of
energy increases. Normally only
available to very large consumers.
process of removing a power plant,
apparatus, equipment, building, or
facility from operation.
process of breaking down organic
material; reduction of the net energy
level and change in physical and
chemical composition of organic
disconnect a transmission and/or
distribution line; a power line that is
not carrying a current; to open a
Discharging a battery to 20 percent or
less of its full charge capacity.
net removal of trees from forested land.
Degree Day A unit
for measuring the extent that the
outdoor daily average temperature (the
mean of the maximum and minimum daily
dry-bulb temperatures) falls below (in
the case of heating, see Heating Degree
Day), or falls above (in the case of
cooling, see Cooling Degree Day) an
assumed base temperature, normally taken
as 65 degrees Fahrenheit, unless
otherwise stated. One degree day is
counted for each degree below (for
heating) or above (in the case of
cooling) the base, for each calendar day
on which the temperature goes below or
above the base.
Degree Hour The
product of 1 hour, and usually the
number of degrees Fahrenheit the hourly
mean temperature is above a base point
(usually 65 degrees Fahrenheit); used in
roughly estimating or measuring the
cooling load in cases where processes
heat, heat from building occupants, and
humidity are relatively unimportant
compared to the dry-bulb temperature.
device that cools air by removing
moisture from it.
volume of gas a well, field, pipeline or
distribution system can supply in a
given period of time.
Demand The rate at
which electricity is delivered to or by
a system, part of a system, or piece of
equipment expressed in kilowatts,
kilovoltamperes, or other suitable unit,
at a given instant or averaged over a
specified period of time.
Demand The rate at
which gas is delivered to or by a system
expressed in cubic feet, therms or
multiples thereof, for a designated
period of time.
Water Heater A type of water heater
that has no storage tank thus
eliminating storage tank stand-by
losses. Cold water travels through a
pipe into the unit, and either a gas
burner or an electric element heats the
water only when needed.
Demand Charge A
charge for the maximum rate at which
energy is used during peak hours of a
billing period. That part of a power
provider service charged for on the
basis of the possible demand as
distinguished from the energy actually
Demand Power see
The ratio of the maximum demand on an
electricity generating and distribution
system to the total connected load on
the system; usually expressed as a
Management (DSM) Refers to the use of
costeffective conservation, efficiency
acquisition, and load management in
order to reduce the demand for and cost
of energy services. Energy efficiency,
generally speaking, refers to
investments that result in reductions in
annual energy use while load management
means shifting the time of that use.
Management (DSM) The process of
managing the consumption of energy,
generally to optimize available and
planned generation resources.
Conservation or efficiency measures.
Energy savings can be considered a
resource in the sense that they make it
possible to serve increased demand
without obtaining new supplies.
Dendrite A slender
threadlike spike of pure crystalline
material, such as silicon.
Technique A method for making sheets
of polycrystalline silicon in which
silicon dendrites are slowly withdrawn
from a melt of silicon whereupon a web
of silicon forms between the dendrites
and solidifies as it rises from the melt
Agriculture (USDA) A federal
government agency involved in rural
development, marketing and regulatory
programs, food safety, research,
education and economics, food, nutrition
and consumer service, farm and foreign
agricultural services, and natural
resources and environment programs.
Department of Energy
(DOE) A federal government agency
created in 1977, that is entrusted to
contribute to the welfare of the United
States by providing technical
information, and a scientific and
educational foundation for technology,
policy and institutional leadership to
achieve efficiency in energy use,
diversity in energy sources, a more
productive and competitive economy,
improved environmental quality, and a
secure national defense.
The load-carrying ability of an electric
power plant during a specific time
interval and period when related to the
characteristics of the load to be/being
supplied; determined by capability,
operating power factor, and the portion
of the load the station is to supply.
production of energy by a system or
appliance at a level less than its
design or nominal capacity.
process of changing regulatory policies
and laws to increase competition among
suppliers of commodities and services.
The process of deregulating the electric
power industry was initiated by the
Energy Policy Act of 1992. (See also
Derrick A frame
tower that supports the drill equipment
used to find oil and natural gas in the
material used to desiccate (dry) or
To condition/cool air by desiccation.
process of removing moisture; involves
Design Cooling Load
The amount of conditioned air to be
supplied by a cooling system; usually
the maximum amount to be delivered based
on a specified number of cooling degree
days or design temperature.
Design Heating Load
The amount of heated air, or heating
capacity, to be supplied by a heating
system; usually the maximum amount to be
delivered based on a specified number of
heating degree days or design outside
Design Life Period
of time a system or appliance (or
component of) is expected to function at
its nominal or design capacity without
The temperature that a system is
designed to maintain (inside) or operate
against (outside) under the most extreme
Design Tip Speed
Ratio For a wind turbine, the ratio of
the speed of the tip of a turbine blade
for which the power coefficient is at
Design Voltage The
nominal voltage for which a conductor or
electrical appliance is designed; the
reference voltage for identification and
not necessarily the precise voltage at
which it operates.
energy saving device in a heat pump
that, during the cooling cycle, recycles
some of the waste heat from the house to
heat domestic water.
temperature to which air must be cooled,
at constant pressure and water vapor
content, in order for saturation or
condensation to occur; the temperature
at which the saturation pressure is the
same as the existing vapor pressure;
also called saturation point.
Diesel Engine Diesel
engines are internal combustion engines
that burn diesel oil rather than
Diesel Fuel A fuel
composed of distillates obtained in
petroleum refining operation or blends
of such distillates with residual oil
used in motor vehicles. The boiling
point and specific gravity are higher
for diesel fuels than for gasoline.
Potential The difference in electrical
pressure (voltage) between any two
points in an electrical system or
between any point in an electrical
system and the earth.
Thermostat A type of automatic
thermostat (used on solar heating
systems) that responds to temperature
differences (between collectors and the
storage components) so as to regulate
the functioning of appliances (to switch
transfer fluid pumps on and off).
Radiation Sunlight scattered by
atmospheric particles and gases so that
it arrives at the earth's surface from
all directions and can not be focused.
movement of individual molecules through
a material; permeation of water vapor
through a material.
The mean distance a free electron or
hole moves before recombining with
another hole or electron.
A device in which organic material is
biochemically decomposed (digested) by
anaerobic bacteria to treat the material
and/or to produce biogas.
Dimmer A light
control device that allows light levels
to be manually adjusted. A dimmer can
save energy by reducing the amount of
power delivered to the light while
consuming very little themselves.
Diode An electronic
device that allows current to flow in
one direction only.
Dip Tube A tube
inside a domestic water heater that
distributes the cold water from the cold
water supply line into the lower area of
the water heater where heating occurs.
Direct Access The
ability of an electric power consumer to
purchase electricity from a supplier of
their choice without being physically
inhibited by the owner of the electric
distribution and transmission system to
which the consumer is connected to. (See
also Open Access.)
Direct Beam Radiation
Solar radiation that arrives in a
straight line from the sun.
Direct Current An
electric current that flows in only one
direction through a circuit, as from a
battery; usually relatively low voltage
and high current; typically abbreviated
Direct Solar Water
Heater These systems use water as the
fluid that is circulated through the
collector to the storage tank. Also
known as "open-loop" systems.
Direct Vent Heater
A type of combustion heating system in
which combustion air is drawn directly
from outside and the products of
combustion are vented directly outside.
These features are beneficial in tight,
energy-efficient homes because they will
not depressurize a home and cause air
infiltration, and backdrafting of other
Direct Water Heater
A type of water heater in which heated
water is stored within the tank. Hot
water is released from the top of the
tank when a hot water faucet is turned.
This water is replaced with cold water
that flows into the tank and down to
just above the bottom plate under which
are the burners.
process by which sunlight directly
enters a building through the windows
and is absorbed and stored in massive
floors or walls.
DIS Department of
Discount Rate The
interest rate at which the Federal
Reserve System stands ready to lend
reserves to commercial banks. The rate
is proposed by the 12 Federal Reserve
banks and determined with the approval
of the Board of Governors.
method of financial and economic
analysis used to determine present and
future values of investments or
ability to dispatch power.
schedule and control the generation and
delivery of electric power.
A source of power (electricity) that can
displace power from another source so
that source's power can be transmitted
to more distant loads.
Distillate Fuel Oil
A general classification for one of the
petroleum fractions produced in
conventional distillation operations. It
includes diesel fuels and fuel oils.
Products known as No. 1, No. 2, and No.
4 diesel fuel are used in onhighway
diesel engines, such as those in trucks
and automobiles, as well as offhighway
engines, such as those in railroad
locomotives and agricultural machinery.
Products known as No. 1, No. 2, and No.
4 fuel oils are used primarily for space
heating and electric power generation.
(atmospheric) The primary distillation
unit that processes crude oil (including
mixtures of other hydrocarbons) at
approximately atmospheric conditions. It
includes a pipe still for vaporizing the
crude oil and a fractionation tower for
separating the vaporized hydrocarbon
components in the crude oil into
fractions with different boiling ranges.
This is done by continuously vaporizing
and condensing the components to
separate higher oiling point material.
Generation A term used by the power
industry to describe localized or
on-site power generation.
process of distributing electricity;
usually defines that portion of a power
provider's power lines between a power
provider's power pole and transformer
and a customer's point of
One or more circuits of a distribution
system on the same line or poles or
supporting structures' usually operating
at a lower voltage relative to the
That portion of an electricity supply
system used to deliver electricity from
points on the transmission system to
District Heating A
heating system in which steam or hot
water for space heating or hot water is
piped from a central boiler plant or
electric power/heating plant to a
cluster of buildings or users.
The ratio of the sum of the
noncoincidental maximum demands of two
or more loads to their coincidental
maximum demands for the same period.
DOE U.S. Department
Dome (Geodesic) An
architectural design invented by
Buckminster Fuller with a regular
polygonal structure based on radial
Domestic Hot Water
Water heated for residential washing,
Donor In a solar
photovoltaic device, an n-type dopant,
such as phosphorus, that puts an
additional electron into an energy level
very near the conduction band; this
electron is easily exited into the
conduction band where it increases the
electrical conductivity over than of an
Dopant A chemical
element (impurity) added in small
amounts to an otherwise pure
semiconductor material to modify the
electrical properties of the material.
An n-dopant introduces more electrons. A
p-dopant creates electron vacancies
Doping The addition
of dopants to a semiconductor.
Double Wall Heat
Exchanger A heat exchanger in a solar
water heating system that has two
distinct walls between the heat transfer
fluid and the domestic water, to ensure
that there is no mixing of the two.
Double-Pane or Glazed
Window A type of window having two
layers (panes or glazing) of glass
separated by an air space. Each layer of
glass and surrounding air space
reradiates and traps some of the heat
that passes through thereby increasing
the windows resistance to heat loss
Downwind Wind Turbine
A horizontal axis wind turbine in
which the rotor is downwind of the
Draft A column of
burning combustion gases that are so hot
and strong that the heat is lost up the
chimney before it can be transferred to
the house. A draft brings air to the
fire to help keep it burning.
Draft Diverter A
door-like device located at the mouth of
a fireplace chimney flue for controlling
the direction and flow of the draft in
the fireplace as well as the amount of
oxygen that the fire receives.
Draft Hood A device
built into or installed above a
combustion appliance to assure the
escape of combustion byproducts, to
prevent backdrafting of the appliance,
or to neutralize the effects of the
stack action of the chimney or vent on
the operation of the appliance.
caused by friction in the direction
opposite to that of movement (i.e.,
motion) of components such as wind
Systems A closed-loop solar heating
system in which the heat transfer fluid
in the collector loop drains into a tank
or reservoir whenever the booster pump
stops to protect the collector loop from
Systems An open-loop solar heating
system in which the heat transfer fluid
from the collector loop and the piping
drain into a drain whenever freezing
Drilling The act of
boring a hole (1) to determine whether
minerals are present in commercially
recoverable quantities and (2) to
accomplish production of the minerals
(including drilling to inject fluids).
There are three types of drilling
exploratory drilling to locate
probable mineral deposits or to
establish the nature of geological
structures; such wells may not be
capable of production if minerals are
discovered; developmental drilling to
delineate the boundaries of a known
mineral deposit to enhance the
productive capacity of the producing
mineral property; and directional
drilling that is deliberately made to
depart significantly from the vertical.
Dry Bulb Temperature
The temperature of the air as measured
by a standard thermometer.
Dry Steam Geothermal
Plants Conventional turbine generators
are used with the dry steam resources.
The steam is used directly, eliminating
the need for boilers and boiler fuel
that characterizes other
This technology is limited because
dry-steam hydrothermal resources are
extremely rare. The Geysers, in
California, is the nation's only dry
Dual Duct System An
air conditioning system that has two
ducts, one is heated and the other is
cooled, so that air of the correct
temperature is provided by mixing
varying amounts of air from each duct.
Dual Fuel (or Flex
Fuel) Vehicle A vehicle with an engine
capable of operating on two different
types of fuels.
Duct Fan An axial
flow fan mounted in a section of duct to
move conditioned air.
Duct(s) The round
or rectangular tube(s), generally
constructed of sheet metal, fiberglass
board, or a flexible plastic-and-wire
composite, located within a wall, floor,
and ceiling that distributes heated or
cooled air in buildings.
Duty Cycle The
duration and periodicity of the
operation of a device.
Dynamic Head The
pressure equivalent of the velocity of a
Dynamo A machine
for converting mechanical energy into
electrical energy by magneto-electric
induction; may be used as a motor.
apparatus for measuring force or power,
especially the power developed by a
Dyne The absolute
centimeter-gram-second unit of force;
that force that will impart to a free
mass of one gram an acceleration of one
centimeter per second per second.
Earth Berm A mound
of dirt next to exterior walls to
provide wind protection and insulation.
Earth Cooling Tube
A long, underground metal or plastic
pipe through which air is drawn. As air
travels through the pipe it gives up
some of its heat to the soil, and enters
the house as cooler air.
Houses Houses that have earth berms
around exterior walls.
Source (Geothermal) Heat Pump A type
of heat pump that uses sealed horizontal
or vertical pipes, buried in the ground,
as heat exchangers through which a fluid
is circulated to transfer heat.
registered trademark name for houses
built with tires, aluminum cans, and
incorporated right, liberty, privilege,
or use of another entity's property,
distinct from ownership, without profit
or compensation; a right-of-way.
Eccentric A device
for converting continuous circular
motion into reciprocating rectilinear
Economizer A heat
exchanger for recovering heat from flue
gases for heating water or air.
Growth (EFG) A method for making
sheets of polycrystalline silicon (for
solar photovoltaic devices) in which
molten silicon is drawn upward by
capillary action through a mold.
The maximum load that a device is
capable of carrying.
Efficacy The amount
of energy service or useful energy
delivered per unit of energy input.
Often used in reference to lighting
systems, where the visible light output
of a luminary is relative to power
input; expressed in lumens per Watt; the
higher the efficacy value, the higher
the energy efficiency.
the First Law of Thermodynamics,
efficiency is the ratio of work or
energy output to work or energy input,
and cannot exceed 100 percent.
Efficiency under the Second Law of
Thermodynamics is determined by the
ratio of the theoretical minimum energy
that is required to accomplish a task
relative to the energy actually consumed
to accomplish the task. Generally, the
measured efficiency of a device, as
defined by the First Law, will be higher
than that defined by the Second Law.
(Appliance) Ratings A measure of the
efficiency of an appliance's energy
Elasticity of Demand
The ratio of the percentage change in
the quantity of a good or service
demanded to the percentage change in the
The path followed by electrons from a
generation source, through an electrical
system, and returning to the source.
Electric Energy The
amount of work accomplished by
electrical power, usually measured in
kilowatt-hours (kWh). One kWh is 1,000
Watts and is equal to 3,413 Btu.
Electric Furnace An
air heater in which air is blown over
electric resistance heating coils.
Electric Motor a
device that takes electrical energy and
converts it into mechanical energy to
turn a shaft.
Electric Power The
amount of energy produced per second.
The power produced by an electric
Electric Power Plant
A facility or piece of equipment that
Electric Power Sector
Those privately or publicly owned
establishments that generate, transmit,
distribute, or sell electricity.
Transmission The transmission of
electricity through power lines.
Electric Rate The
unit price and quantity to which it
applies as specified in a rate schedule
Schedule A statement of the electric
rate(s), terms, and conditions for
electricity sale or supply.
Heating A type of heating system where
heat, resulting when electric current
flows through an "element" or conductor,
such as Nichrome, which has a high
resistance, is radiated to a room.
Electric System The
physically connected generation,
transmission, and distribution
facilities and components operated as a
Loss(es) The total amount of electric
energy loss in an electric system
between the generation source and points
Electric Utility - A
corporation, person, agency, authority
or other legal entity that owns and/or
operates facilities for the generation,
transmission, distribution or sale of
electricity primarily for use by the
public. Also known as a power provider.
Electric Vehicles A
battery-powered electrically driven
Electrical Charge A
condition that results from an imbalance
between the number of protons and the
number of electrons in a substance.
The energy associated with electric
charges and their movements. The energy
of moving electrons.
All the conductors and electricity using
devices that are connected to a source
of electromotive force (or generator).
Energy Losses A measure of the amount
of energy lost during the generation,
transmission, and distribution of
Electricity A form
of energy characterized by the presence
and motion of elementary charged
particles generated by friction,
induction, or chemical change.
Generation The process of producing
electric energy or the amount of
electric energy produced by transforming
other forms of energy, commonly
expressed in kilowatthours (kWh) or
Electricity Grid A
common term referring to an electricity
transmission and distribution system.
Restructuring The process of changing
the structure of the electric power
industry from one of guaranteed monopoly
over service territories, as established
by the Public Utility Holding Company
Act of 1935, to one of open competition
between power suppliers for customers in
A device containing two conducting
electrodes, one positive and the other
negative, made of dissimilar materials
(usually metals) that are immersed in a
chemical solution (electrolyte) that
transmits positive ions from the
negative to the positive electrode and
thus forms an electrical charge. One or
more cells constitute a battery.
The branch of chemistry that deals with
the chemical changes produced by
electricity and the production of
electricity by chemical changes.
conductor that is brought in conducting
contact with a ground.
Electrolytic process in which a metal is
deposited at the cathode from a solution
of its ions.
chemical change in a substance that
results from the passage of an electric
current through an electrolyte. The
production of commercial hydrogen by
separating the elements of water,
hydrogen, and oxygen, by charging the
water with an electrical current.
nonmetallic (liquid or solid) conductor
that carries current by the movement of
ions (instead of electrons) with the
liberation of matter at the electrodes
of an electrochemical cell.
Having to do with magnetism produced by
an electric current.
Energy Energy generated from an
electromagnetic field produced by an
electric current flowing through a
superconducting wire kept at a specific
low temperature. it travels in waves,
such as ultraviolet radiation. It can
be thought of as a combination of
electric and magnetic energy.
(EMF) The electrical and magnetic
fields created by the presence or flow
of electricity in an electrical
conductor or electricity consuming
appliance or motor.
Radiation that consists of traveling
waves of electric and magnetic
disturbances. Xrays, light rays and
radio waves are among the many kinds of
The amount of energy derived from an
electrical source per unit quantity of
electricity passing through the source.
elementary particle (subatomic) of an
atom with a negative electrical charge
and a mass of 1/1837 of a proton;
electrons surround the positively
charged nucleus of an atom and determine
the chemical properties of an atom.
Electron Volt The
amount of kinetic energy gained by an
electron when accelerated through an
electric potential difference of 1 Volt;
equivalent to 1.603 x 10^-12; a unit of
energy or work; abbreviated as eV.
A device that uses electronic components
to regulate the voltage of fluorescent
Precipitator A device used to remove
particulate matter from the waste gasses
of a combustion power plant.
substance that cannot be separated into
different substances. All matter is
composed of elements.
Lamp A lamp where the light beam is
focused 2 inches ahead of the lamp
reducing the amount of light trapped in
discharge or something that is given
off; generally used in regard to
discharges into the air. Or, releases of
gases to the atmosphere from some type
of human activity (cooking, driving a
car, etc). In the context of global
climate change, they consist of
greenhouse gases (e.g., the release of
carbon dioxide during fuel combustion).
Emission Factor A
measure of the average amount of a
specified pollutant or material emitted
for a specific type of fuel or process.
substance(s) or pollutant emitted as a
result of a process.
ratio of the radiant energy (heat)
leaving (being emitted by) a surface to
that of a black body at the same
temperature and with the same area;
expressed as a number between 0 and 1.
housing around a motor that supports the
active parts and protects them. They
come in different varieties (open,
protected) depending on the degree of
End Use The purpose
for which useful energy or work is
Endothermic A heat
absorbing reaction or a reaction that
Energize(d) To send
electricity through a electricity
transmission and distribution network; a
conductor or power line that is carrying
Energy The ability
to do work or the ability to move an
object. Electrical energy is usually
measured in kilowatthours (kWh), while
heat energy is usually measured in
British thermal units (Btu). Different
forms of energy can be converted to
other forms, but the total amount of
energy remains the same.
Energy Audit A
survey that shows how much energy you
use in your house or apartment. It will
help you find ways to use less energy.
Energy Charge That
part of an electricity bill that is
based on the amount of electrical energy
consumed or supplied.
The use of energy as a source of heat or
power or as a raw material input to a
Potential Recombination occurring in
the emitter region of a photovoltaic
Energy Crops Crops
grown specifically for their fuel value.
These include food crops such as corn
and sugarcane, and nonfood crops such as
poplar trees and switchgrass. Currently,
two energy crops are under development:
short-rotation woody crops, which are
fast-growing hardwood trees harvested in
5 to 8 years; and herbaceous energy
crops, such as perennial grasses, which
are harvested annually after taking 2 to
3 years to reach full productivity.
Energy Density The
ratio of available energy per pound;
usually used to compare storage
Refers to activities that are aimed at
reducing the energy used by substituting
technically more advanced equipment,
typically without affecting the services
provided. Examples include
highefficiency appliances, efficient
lighting programs, highefficiency
heating, ventilating and air
conditioning (HVAC) systems or control
modifications, efficient building
design, advanced electric motor drives,
and heat recovery systems.
Ratio (EER) The measure of the
instantaneous energy efficiency of room
air conditioners; the cooling capacity
in Btu/hr divided by the watts of power
consumed at a specific outdoor
temperature (usually 95 degrees
Mortgages A type of home mortgage that
takes into account the energy savings of
a home that has cost-effective energy
saving improvements that will reduce
energy costs thereby allowing the
homeowner to more income to the mortgage
payment. A borrower can qualify for a
larger loan amount than otherwise would
Sectors Major energy consuming sectors
of the economy. The Commercial Sector
includes commercial buildings and
private companies. The Industrial Sector
includes manufacturers and processors.
The Residential Sector includes private
homes. The Transportation Sector
includes automobiles, trucks, rail,
ships, and aircraft.
Energy Factor (EF)
The measure of overall efficiency for a
variety of appliances. For water
heaters, the energy factor is based on
three factors: 1) the recovery
efficiency, or how efficiently the heat
from the energy source is transferred to
the water; 2) stand-by losses, or the
percentage of heat lost per hour from
the stored water compared to the content
of the water: and 3) cycling losses. For
dishwashers, the energy factor is
defined as the number of cycles per kWh
of input power. For clothes washers, the
energy factor is defined as the cubic
foot capacity per kWh of input power per
cycle. For clothes dryers, the energy
factor is defined as the number of
pounds of clothes dried per kWh of power
Energy Guide Labels
The labels placed on appliances to
enable consumers to compare appliance
energy efficiency and energy consumption
under specified test conditions as
required by the Federal Trade
The relative extent that energy is
required for a process.
Energy Policy Act of
1992 (EPAct) A comprehensive
legislative package that mandates and
encourages energy efficiency standards,
alternative fuel use, and the
development of renewable energy
technologies. Public Law 102-486,
October 24th, 1992. Also authorized the
Federal Energy Regulatory Commission
(FERC) to order the owners of electric
power transmission lines to transmit or
"wheel" power for power generators
including electric power providers,
federal power marketing authorities, and
exempt wholesale generators.
Energy Security Act
of 1980 Legislation authorizing a U.S.
biomass and alcohol fuel program, and
that authorized loan guarantees and
price guarantees and purchase agreements
for alcohol fuel production.
Company (ESCO) A company that
specializes in undertaking energy
efficiency measures under a contractual
arrangement whereby the ESCO shares the
value of energy savings with their
Energy Storage The
process of storing, or converting energy
from one form to another, for later use;
storage devices and systems include
batteries, conventional and pumped
storage hydroelectric, flywheels,
compressed gas, and thermal mass.
thermodynamic property of a substance,
defined as the sum of its internal
energy plus the pressure of the
substance times its volume, divided by
the mechanical equivalent of heat. The
total heat content of air; the sum of
the enthalpies of dry air and water
vapor, per unit weight of dry air;
measured in Btu per pound (or calories
Gasifier A gasifier in which the
feedstock (fuel) is suspended by the
movement of gas to move it through the
Entropy A measure
of the unavailable or unusable energy in
a system; energy that cannot be
converted to another form.
Environment All the
natural and living things around us. The
earth, air, weather, plants, and animals
all make up our environment.
Epitaxial Growth In
reference to solar photovoltaic devices,
the growth of one crystal on the surface
of another crystal. The growth of the
deposited crystal is oriented by the
lattice structure of the original
Equinox The two
times of the year when the sun crosses
the equator and night and day are of
equal length; usually occurs on March
21st (spring equinox) and September 23
Erg A unit of work
done by the force of one dyne acting
through a distance of one centimeter.
alcohol (C2H5OH) A colorless liquid
that is the product of fermentation used
in alcoholic beverages, industrial
processes, and as a fuel additive. Also
known as grain alcohol. A liquid that
burns to produce water and carbon
dioxide. The vapor forms an explosive
mixture with air and may be used as a
fuel in internal combustion engines.
Tertiary Butyl Ether (ETBE) A chemical
compound produced in a reaction between
ethanol and isobutylene (a
petroleum-derived by-product of the
refining process). ETBE has
characteristics superior to other
ethers: low volatility, low water
solubility, high octane value, and a
large reduction in carbon monoxide and
Eutectic A mixture
of substances that has a melting point
lower than that of any mixture of the
same substances in other proportions.
Eutectic Salts Salt
mixtures with potential applications as
solar thermal energy storage materials.
Collector A collector is the mechanism
in which fluid (water or diluted
antifreeze, for example) is heated by
the sun in a solar hot water system.
Evacuated-tube collectors are made up of
rows of parallel, transparent glass
tubes. Each tube consists of a glass
outer tube and an inner tube, or
absorber. The absorber is covered with a
selective coating that absorbs solar
energy well but inhibits radiative heat
loss. The air is withdrawn ("evacuated")
from the space between the tubes to form
a vacuum, which eliminates conductive
and convective heat loss. Evacuated-tube
collectors are used for active solar hot
conversion of a liquid to a vapor (gas),
usually by means of heat.
The physical process by which a liquid
or solid is transformed into the gaseous
state. For this process a mechanical
device uses the outside air's heat to
evaporate water that is held by pads
inside the cooler. The heat is drawn out
of the air through this process and the
cooled air is blown into the home by the
Evaporator Coil The
inner coil in a heat pump that, during
the cooling mode, absorbs heat from the
inside air and boils the liquid
refrigerant to a vapor, which cools the
power required to energize the magnetic
field of a generator.
Generator An unregulated subsidiary of
a power provider that is allowed to
generate and sell wholesale power as an
independent energy producer, and is
exempt from the Public Utility Holding
Company Act of 1935.
reaction or process that produces heat;
a combustion reaction.
A type of insulation that is molded or
expanded to produce coarse, closed cells
containing air. The rigid cellular
structure provides thermal and
acoustical insulation, strength with low
weight, and coverage with few heat loss
paths. Often used to insulate the
interior of masonry basement walls.
Expansion Tank A
tank used in a closed-loop solar heating
system that provides space for the
expansion of the heat transfer fluid in
the pressurized collector loop.
Expansion Valve The
device that reduces the pressure of
liquid refrigerant thereby cooling it
before it enters the evaporator coil in
a heat pump.
Engine An engine in which fuel is
burned (or heat is applied) to the
outside of a cylinder; a Stirling
environmental, social, and economic
impacts of producing a good or service
that are not directly reflected in the
market price of the good or service.
A type of insulation material with
fine, closed cells, containing a mixture
of air and refrigerant gas. This
insulation has a high R-value, good
moisture resistance, and high structural
strength compared to other rigid
Fan A device that
moves and/or circulates air and provides
ventilation for a room or a building.
Fan Coil A heat
exchanger coil in which a fluid such as
water is circulated and a fan blows air
over the coil to distribute heat or cool
air to the different rooms.
Fan Velocity Pressure
The pressure corresponding to the
outlet velocity of a fan; the kinetic
energy per unit volume of flowing air.
Farad A unit of
electrical capacitance; the capacitance
of a capacitor between the plates of
which there appears a difference of 1
Volt when it is charged by one coulomb
Feather In a wind
energy conversion system, to pitch the
turbine blades so as to reduce their
lift capacity as a method of shutting
down the turbine during high wind
Management Program (FEMP) A program of
the U.S. Department of Energy (DOE) that
implements energy legislation and
presidential directives. FEMP provides
project financing, technical guidance
and assistance, coordination and
reporting, and new initiatives for the
federal government. It also helps
federal agencies identify the best
technologies and technology
demonstrations for their use.
Regulatory Commission (FERC) This is
an independent regulatory agency within
the U.S. DOE that has jurisdiction over
interstate electricity sales, wholesale
electric rates, natural gas pricing, oil
pipeline rates, and gas pipeline
certification. It also licenses and
inspects private, municipal, and state
hydroelectric projects and oversees
related environmental matters.
Marketing Administrations (PMA) These
are separate and distinct organizational
agencies within the U.S. DOE that market
power at federal multipurpose water
projects at lowest possible rates to
consumers consistent with sound business
principles. There are five PMA's: Alaska
Power Administration, Bonneville Power
Administration, Southeastern Power
Administration, Southwestern Power
Administration, Western Area Power
Feeder A power line
for supplying electricity within a
Feedstock A raw
material that can be converted to one or
arrangement, proportion, and design of
windows in a building.
FERC Federal Energy
decomposition of organic material to
alcohol, methane, etc., by organisms,
such as yeast or bacteria, usually in
the absence of oxygen.
A type of insulation, composed of
small diameter pink, yellow, or white
glass fibers, formed into blankets or
batts, or used in loose-fill and
Filament A coil of
tungsten wire suspended in a vacuum or
inert gas-filled bulb. When heated by
electricity the tungsten "filament"
Fill Factor The
ratio of a photovoltaic cell's actual
power to its power if both current and
voltage were at their maxima. A key
characteristic in evaluating cell
Filter (air) A
device that removes contaminants, by
mechanical filtration, from the fresh
air stream before the air enters the
living space. Filters can be installed
as part of a heating/cooling system
through which air flows for the purpose
of removing particulates before or after
the air enters the mechanical
Fin A thin sheet of
material (metal) of a heat exchanger
that conducts heat to a fluid.
Finish Both a noun
and a verb to describe the exterior
surface of building elements (walls,
floors, ceilings, etc.) and furniture,
and the process of applying it.
Classifications of fires developed by
the National Fire Protection
Fireplace A wood or
gas burning appliance that is primarily
used to provide ambiance to a room.
Conventional, masonry fireplaces without
energy saving features, often take more
heat from a space than they put into it.
Fireplace Insert A
wood or gas burning heating appliance
that fits into the opening or protrudes
on to the hearth of a conventional
Fire-Rating - The
ability of a building construction
assembly (partition, wall, floor, etc.)
to resist the passage of fire. The
rating is expressed in hours.
Firewall A wall to
prevent the spread of fire; usually made
of non-combustible material.
Firing Rate The
amount of BTUs/hour or kWs produced by a
heating system from the burning of a
Firm power The
portion of a customer's energy load for
which service is assured by the utility
Firm service Sales
or transportation service that is not
subject to prior claim by another
customer or class of service. The
highest quality service offered to
Natural gas transportation services for
which facilities have been designed,
installed, and dedicated to a certified
volume. Firm transportation service
takes priority over interruptible
First Law of
Thermodynamics States that energy
cannot be created or destroyed, but only
changed from one form to another. First
Law efficiency measures the fraction of
energy supplied to a device or process
that it delivers in its output. Also
called the law of conservation of
Fiscal Year (FY)
The U.S. Government's 12-month financial
year, from October to September, of the
following calender year; e.g.: FY 1998
extends from Oct. 1, 1997 to Sept. 30,
splitting apart of atoms. This splitting
releases large amounts of energy and one
or more neutrons. Nuclear power plants
split the nuclei of uranium atoms in a
process called fission.
Classification A measure of the
surface burning characteristics of a
Flame Spread Rating
A measure of the relative flame spread,
and smoke development, from a material
being tested. The flame spread rating is
a single number comparing the flame
spread of a material with red oak,
arbitrarily given the number 100 and
asbestos cement board with a flame
spread of 0. Building codes require a
maximum flame spread of 25 for
insulation installed in exposed
usually galvanized sheet metal, used to
provide protection against infiltration
of precipitation into a roof or exterior
wall; usually placed around roof
penetrations such as chimneys.
minimum temperature at which sufficient
vapor is released by a liquid or solid
(fuel) to form a flammable vapor-air
mixture at atmospheric pressure.
Geothermal Plants When the temperature
of the hydrothermal liquids is over 350
F (177 C), flash-steam technology is
generally employed. In these systems,
most of the liquid is flashed to steam.
The steam is separated from the
remaining liquid and used to drive a
turbine generator. While the water is
returned to the geothermal reservoir,
the economics of most hydrothermal flash
plants are improved by using a
dual-flash cycle, which separates the
steam at two different pressures. The
dual-flash cycle produces 20% to 30%
more power than a single-flash system at
the same fluid flow.
Flat Plate Solar
Photovoltaic Module An arrangement of
photovoltaic cells or material mounted
on a rigid flat surface with the cells
exposed freely to incoming sunlight.
Flat Plate Solar
Thermal/Heating Collectors Large, flat
boxes with glass covers and dark-colored
metal plates inside that absorb and
transfer solar energy to a heat transfer
fluid. This is the most common type of
collector used in solar hot water
systems for homes or small businesses.
Flat Roof A
slightly sloped roof, usually with a tar
and gravel cover. Most commercial
buildings use this kind of roof.
Nonglossy paint with a relatively high
Connector A device designed to capture
the suns energy and produce low
temperature heat energy. They are
commonly used as collectors in solar
In reference to solar photovoltaic cell
manufacture, a method of growing a
large-size, high-quality crystal whereby
coils heat a polycrystalline ingot
placed atop a single-crystal seed. As
the coils are slowly raised the molten
interface beneath the coils becomes a
Floor The upward
facing structure of a building.
Floor Space The
interior area of a building, calculated
in square feet or meters.
Flow To move or run
smoothly with unbroken continuity, as in
the manner characteristic of a fluid.
Flow Condition In
reference to solar thermal collectors,
the condition where the heat transfer
fluid is flowing through the collector
loop under normal operating conditions.
Flow Restrictor A
water and energy conserving device that
limits the amount of water that a faucet
or shower head can deliver.
Flue The structure
(in a residential heating appliance,
industrial furnace, or power plant) into
which combustion gases flow and are
contained until they are emitted to the
Flue Gas The gas
resulting from the combustion of a fuel
that is emitted to the flue.
practice of installing blow-in,
loose-fill insulation at a lower density
than is recommended to meet a specified
Combustion (FBC) A type of furnace or
reactor in which fuel particles are
combusted while suspended in a stream of
The conversion of electric power to
visible light by using an electric
charge to excite gaseous atoms in a
glass tube. These atoms emit ultraviolet
radiation that is absorbed by a phosphor
coating on the walls of the lamp tube.
The phosphor coating produces visible
Fly Ash The fine
particulate matter entrained in the flue
gases of a combustion power plant.
Flywheel Effect The
damping of interior temperature
fluctuations by massive construction.
Foam (Insulation) A
high R-value insulation product usually
made from urethane that can be injected
into wall cavities, or sprayed onto
roofs or floors, where it expands and
Foam Board A
plastic foam insulation product, pressed
or extruded into board-like forms, used
as sheathing and insulation for interior
basement or crawl space walls or beneath
a basement slab; can also be used for
exterior applications inside or outside
foundations, crawl spaces, and
slab-on-grade foundation walls.
Foam Core Panels A
type of structural, insulated product
with foam insulation contained between
two facings of drywall, or structural
wood composition boards such as plywood,
waferboard, and oriented strand board.
Foot Candle A unit
of illuminance; equal to one lumen per
Foot Pound The
amount of work done in raising one pound
which changes the state of rest or
motion of something. The push or pull
that alters the motion of a moving body
or moves a stationary body; the unit of
force is the dyne or poundal; force is
equal to mass time velocity divided by
Forced Air System or
Furnace A type of heating system in
which heated air is blown by a fan
through air channels or ducts to rooms.
A type of building ventilation system
that uses fans or blowers to provide
fresh air to rooms when the forces of
air pressure and gravity are not enough
to circulate air through a building.
chemical used as a preservative and in
bonding agents. It is found in household
products such as plywood, furniture,
carpets, and some types of foam
insulation. It is also a by-product of
combustion and is a strong-smelling,
colorless gas that is an eye irritant
and can cause sneezing, coughing, and
other health problems.
Fossil Fuels Fuels
formed in the ground that result from
the compression of ancient plant and
animal life formed over millions of
years. It takes millions of years to
form fossil fuels. Oil, natural gas, and
coal are fossil fuels.
supportive structure of a building.
Power Motor An electric motor rated at
less than one horse power (hp).
Frame (Window) The
outer casing of a window that sits in a
designated opening of a structure and
holds the window panes in place.
structural materials and elements used
to construct a wall.
Francis Turbine A
type of hydropower turbine that contains
a runner that has water passages through
it formed by curved vanes or blades. As
the water passes through the runner and
over the curved surfaces, it causes
rotation of the runner. The rotational
motion is transmitted by a shaft to a
Freon A registered
trademark for a cholorfluorocarbon (CFC)
gas that is highly stable and that has
been historically used as a refrigerant.
number of cycles through which an
alternating current passes per second;
in the U.S. the standard for electricity
generation is 60 cycles per second (60
Fresnel Lens An
optical device for concentrating light
that is made of concentric rings that
are faced at different angles so that
light falling on any ring is focused to
the same point.
Friction Head The
energy lost from the movement of a fluid
in a conduit (pipe) due to the
disturbances created by the contact of
the moving fluid with the surfaces of
the conduit, or the additional pressure
that a pump must provide to overcome the
resistance to fluid flow created by or
in a conduit.
Fuel Any material
that can be burned to make energy.
Fuel cell A
cogeneration device that converts
energy, such as natural gas, directly
into electricity and heat without an
intermediate combustion step. Hydrogen
from Natural gas and oxygen from the air
are combined to produce electricity. The
heat from the electrochemical process
heats water, which then can be used in
commercial and industrial heating
Fuel Cycle The
entire set of stages involved in the
utilization of fuel, including
transportation, and combustion.
Fuel Efficiency The
ratio of heat produced by a fuel for
doing work to the available heat in the
Fuel Grade Alcohol
Usually refers to ethanol to 160 to 200
Fuel Oil An oil
that is used for fuel and that usually
ignites at a higher temperature than
kerosene. Any liquid petroleum product
burned for the generation of heat in a
furnace or firebox, or for the
generation of power in an engine.
Domestic (residential) heating fuels are
classed as Nos. 1, 2, 3; Industrial
fuels as Nos. 4, 5, and 6.
Fuel Rate The
amount of fuel necessary to generate one
kilowatt-hour of electricity.
Full Sun The amount
of power density in sunlight received at
the earth's surface at noon on a clear
day (about 1,000 Watts/square meter).
organisms with cells with distinct
nuclei surrounded by nuclear membranes,
incapable of photosynthesis. Fungi are
decomposers of waste organisms and exist
as yeast, mold, or mildew.
Furling The process
of forcing, either manually or
automatically, a wind turbine's blades
out of the direction of the wind in
order to stop the blades from turning.
Furnace An enclosed
structure in which heat is produced for
the purpose of heating a house or a
A combustion heating appliance in
which heat is captured from the burning
of a fuel for distribution, comprised
mainly of a combustion chamber and heat
Fuse A safety
device consisting of a short length of
relatively fine wire, mounted in a
holder or contained in a cartridge and
connected as part of an electrical
circuit. If the circuit source current
exceeds a predetermined value, the fuse
wire melts (i.e. the fuse 'blows')
breaking the circuit and preventing
damage to the circuit protected by the
Fusion When the
nuclei of atoms are combined or "fused"
together. The sun combines the nuclei of
hydrogen atoms into helium atoms in a
process called fusion. Energy from the
nuclei of atoms, called "nuclear energy"
is released from fusion.
Gallium Arsenide A
compound used to make certain types of
solar photovoltaic cells.
Gallon A measure of
volume equal to 4 quarts (231 cubic
inches). One barrel equals 42 gallons.
Gas (1) A
nonsolid, nonliquid (as hydrogen or
air) substance that has no fixed shape
and tends to expand without limit. (2) A
state of matter in which the matter
concerned occupies the whole of its
container irrespective of its quantity.
Includes natural gas, cokeoven gas,
blast furnace gas, and refinery gas.
Gas To Liquids (GTL)
A process that combines the carbon and
hydrogen elements in natural gas
molecules to make synthetic liquid
petroleum products, such as diesel fuel.
Gas Turbine A type
of turbine in which combusted,
pressurized gas is directed against a
series of blades connected to a shaft,
which forces the shaft to turn to
produce mechanical energy.
Gas Turbine Plant A
plant in which the prime mover is a gas
turbine. A gas turbine consists
typically of an axialflow air
compressor and one or more combustion
chambers where liquid or gaseous fuel is
burned and the hot gases are passed to
the turbine and where the hot gases
expand drive the generator and are then
used to run the compressor.
process in which a solid fuel is
converted into a gas; also known as
pyrolitic distillation or pyrolysis.
Production of a clean fuel gas makes a
wide variety of power options available.
Gasifier A device
for converting a solid fuel to a gaseous
Gasket/Seal A seal
used to prevent the leakage of fluids,
and also maintain the pressure in an
registered trademark of an agency of the
state of Nebraska, for an automotive
fuel containing a blend of 10 percent
ethanol and 90 percent gasoline.
Gasoline A refined
petroleum product made up of a complex
mixture of relatively volatile
hydrocarbons with or without small
quantities of additives, blended to form
a fuel suitable for use in
sparkignition or internal combustion
Gauss The unit of
magnetic field intensity equal to 1 dyne
per unit pole.
The amount of electrical power a power
plant can produce.
Generator A device
that turns mechanical energy into
electrical energy. The mechanical energy
is sometimes provided by an engine or
These brines are hot (300 F to 400 F)
(149 C to 204 C) pressurized waters that
contain dissolved methane and lie at
depths of 10,000 ft (3048 m) to more
than 20,000 ft (6096 m) below the
earth's surface. The best known
geopressured reservoirs lie along the
Texas and Louisiana Gulf Coast. At least
three types of energy could be obtained:
thermal energy from high-temperature
fluids; hydraulic energy from the high
pressure; and chemical energy from
burning the dissolved methane gas.
Energy produced by the natural processes
inside the earth; geothermal heat
sources include: hydrothermal convective
systems; pressurized water reservoirs;
hot dry rocks; manual gradients; and
magma. Geothermal energy can be used
directly for heating or to produce
Geothermal Heat Pump
A type of heat pump that uses the
ground, ground water, or ponds as a heat
source and heat sink, rather than
outside air. Ground or water
temperatures are more constant and are
warmer in winter and cooler in summer
than air temperatures. Geothermal heat
pumps operate more efficiently than
"conventional" or "air source" heat
Station An electricity generating
facility that uses geothermal energy.
Gigawatt (GW) A
unit of power equal to 1 billion Watts;
1 million kilowatts, or 1,000 megawatts.
Gin Pole A pole
used to assist in raising a tower.
discomfort or interference with visual
perception when viewing a bright object
against a dark background.
Glauber's Salt A
salt, sodium sulfate decahydrate, that
melts at 90 degrees Fahrenheit; a
component of eutectic salts that can be
used for storing heat.
Glazing A term used
for transparent or translucent material
(glass or plastic) used to admit light
and/or to reduce heat loss; used for
building windows, skylights, or
greenhouses, or for covering the
aperture of a solar collector.
Global Insolation (or
Solar Radiation) The total diffuse and
direct insolation on a horizontal
surface, averaged over a specified
period of time.
Global Warming A
popular term used to describe the
increase in average global temperatures
due to the greenhouse effect. It is an
increase in the near surface temperature
of the Earth. Global warming has
occurred in the distant past as the
result of natural influences, but the
term is today most often used to refer
to the warming some scientists predict
will occur as a result of increased
anthropogenic emissions of greenhouse
Governor A device
used to regulate motor speed, or, in a
wind energy conversion system, to
control the rotational speed of the
Ethanol.Gravity The natural force of
attraction of the mass of a heavenly
body (as the earth) for bodies at or
near its surface.
Green certificates represent the
environmental attributes of power
produced from renewable resources. By
separating the environmental attributes
from the power, clean power generators
are able to sell the electricity they
produce to power providers at a
competitive market value. The additional
revenue generated by the sale of the
green certificates covers the
above-market costs associated with
producing power made from renewable
energy sources. Also known as green
tags, renewable energy certificates, or
tradable renewable certificates.
Green Power A
popular term for energy produced from
clean, renewable energy resources.
Green Pricing In
the case of renewable electricity, green
pricing represents a market solution to
the various problems associated with
regulatory valuation of the non-market
benefits of renewables. Green pricing
programs allow electricity customers to
express their willingness to pay for
renewable energy development through
direct payments on their monthly utility
Greenhouse Effect A
term used to describe the heating effect
due to the trapping of long wave
(length) radiation by greenhouse gases
produced from natural and human sources,
in keeping the Earths surface warmer
than it would be otherwise, with the
atmosphere acting like a greenhouse.
Waste gases given off by industrial
and power plants, automobiles and other
Gases that trap the heat of the sun in
the Earth's atmosphere, producing the
greenhouse effect. The two major
greenhouse gases are water vapor and
carbon dioxide. Lesser greenhouse gases
include methane, ozone,
chlorofluorocarbons, and nitrogen
oxides. They are transparent to solar
radiation, but opaque to long wave
radiation, which contributes to the
cut, unseasoned, wood.
water from a household source other than
a toilet. This water can be used for
landscape irrigation depending upon the
source of the greywater.
Grid A common term
referring to an electricity transmission
and distribution system. The layout of
an electrical distribution system.
Independent power systems that are
connected to an electricity transmission
and distribution system (referred to as
the electricity grid) such that the
systems can draw on the grid's reserve
capacity in times of need, and feed
electricity back into the grid during
times of excess production.
Gross Calorific Value
The heat produced by combusting a
specific quantity and volume of fuel in
an oxygen-bomb colorimeter under
The total amount of electricity produced
by a power plant.
Ground A device
used to protect the user of any
electrical system or appliance from
Ground Loop In
geothermal heat pump systems, a series
of fluid-filled plastic pipes buried in
the shallow ground, or placed in a body
of water, near a building. The fluid
within the pipes is used to transfer
heat between the building and the
shallow ground (or water) in order to
heat and cool the building.
Solar radiation reflected from the
ground onto a solar collector.
Pump (see geothermal systems)
Guy Wire Cable use
to secure a wind turbine tower to the
ground in a safe, stable manner.
sinusoidal quantity having a frequency
that is an integral multiple of the
frequency of a periodic quantity to
which it is related.
Head A unit of
pressure for a fluid, commonly used in
water pumping and hydro power to express
height a pump must lift water, or the
distance water falls. Total head
accounts for friction head losses, etc.
Heat A form of
thermal energy resulting from
combustion, chemical reaction, friction,
or movement of electricity. As a
thermodynamic condition, heat, at a
constant pressure, is equal to internal
or intrinsic energy plus pressure times
Heat Absorbing Window
Glass A type of window glass that
contains special tints that cause the
window to absorb as much as 45% of
incoming solar energy, to reduce heat
gain in an interior space. Part of the
absorbed heat will continue to be passed
through the window by conduction and
Heat Balance Energy
output from a system that equals energy
Heat Content The
amount of heat in a quantity of matter
at a specific temperature and pressure.
The gross heat content is the number of
British thermal units (Btu) produced by
the combustion, of a volume of gas under
certain with air of the same temperature
and pressure as the gas, when the
products of combustion are cooled to the
initial temperature of gas and air and
when the water formed by combustion is
condensed to the liquid state.
Heat Engine A
device that produces mechanical energy
directly from two heat reservoirs of
different temperatures. A machine that
converts thermal energy to mechanical
energy, such as a steam engine or
Heat Exchanger A
device used to transfer heat from a
fluid (liquid or gas) to another fluid
where the two fluids are physically
separated or to the environment.
Heat Gain The
amount of heat introduced to a space
from all heat producing sources, such as
building occupants, lights, appliances,
and from the environment, mainly solar
Heat Loss The heat
that flows from the building interior,
through the building envelope to the
Heat Pipe A device
that transfers heat by the continuous
evaporation and condensation of an
Heat Pump An
electricity powered device that extracts
available heat from one area (the heat
source) and transfers it to another (the
heat sink) to either heat or cool an
interior space or to extract heat energy
from a fluid.
Heat Pump Water
Heaters A water heater that uses
electricity to move heat from one place
to another instead of generating heat
Heat Rate The ratio
of fuel energy input as heat per unit of
net work output; a measure of a power
plant thermal efficiency, generally
expressed as Btu per net kilowatt-hour.
Ventilator A device that captures the
heat from the exhaust air from a
building and transfers it to the
supply/fresh air entering the building
to preheat the air and increase overall
Heat Register The
grilled opening into a room by which the
amount of warm air from a furnace can be
directed or controlled; may include a
Heat Sink A
structure or media that absorbs heat.
Heat Source A
structure or media from which heat can
be absorbed or extracted.
Heat Storage A
device or media that absorbs heat for
storage for later use.
Heat Storage Capacity
The amount of heat that a material can
absorb and store.
Heat Transfer The
flow of heat from one area to another by
conduction, convection, and/or
radiation. Heat flows naturally from a
warmer to a cooler material or space.
Heat Transfer Fluid
A gas or liquid used to move heat energy
from one place to another; a
Coefficient Any coefficient used to
calculate heat transmission by
conduction, convection, or radiation
through materials or structures.
(Also specific heat) The quantity of
heat necessary to raise the temperature
of a specific mass of a substance by one
Heating Degree Day(s)
(HDD) The number of degrees per day
that the daily average temperature (the
mean of the maximum and minimum recorded
temperatures) is below a base
temperature, usually 65 degrees
Fahrenheit, unless otherwise specified;
used to determine indoor space heating
requirements and heating system sizing.
Total HDD is the cumulative total for
the year/heating season. The higher the
HDD for a location, the colder the daily
Any equipment designed and/or
specifically used for heating ambient
air in an enclosed space. Common types
of heating equipment include central
warm air furnace, heat pump, plugin or
builtin room heater, boiler for steam
or hot water heating system, heating
stove, and fireplace.
Heating Fuel Units
Standardized weights or volumes for
Heating Fuels Any
gaseous, liquid, or solid fuel used for
indoor space heating.
Heating Load The
rate of heat flow required to maintain a
specific indoor temperature; usually
measured in Btu per hour.
Heating Season The
coldest months of the year; months where
average daily temperatures fall below 65
degrees Fahrenheit creating demand for
indoor space heating.
Performance Factor (HSPF) The measure
of seasonal or annual efficiency of a
heat pump operating in the heating mode.
It takes into account the variations in
temperature that can occur within a
season and is the average number of Btu
of heat delivered for every watt-hour of
electricity used by the heat pump over a
Heating Value The
amount of heat produced from the
complete combustion of a unit of fuel.
The higher (or gross) heating value is
that when all products of combustion are
cooled to the pre-combustion
temperature, water vapor formed during
combustion is condensed, and necessary
corrections have been made. Lower (or
net) heating value is obtained by
subtracting from the gross heating value
the latent heat of vaporization of the
water vapor formed by the combustion of
the hydrogen in the fuel.
and Air-Conditioning (HVAC) System All
the components of the appliance used to
condition interior air of a building.
The utilization of solar energy
Heliodon A device
used to simulate the angle of the sun
for assessing shading potentials of
building structures or landscape
suntracking mirrors used to reflect and
concentrate the suns' energy onto a
central receiver tower; used to orient
solar concentrating systems.
process that uses solar radiation to
produce useful heat.
planning that accounts for natural solar
heating and cooling processes and their
relationship to building shape,
orientation, and siting.
instrument for measuring solar
device (or plant) that follows the sun's
apparent movement across the sky.
Technology A solar energy
concentrating technology that uses a
linear receiver that tracks the focal
area of a reflector or array of
Hertz A measure of
the number of cycles or wavelengths of
electrical energy per second; U.S.
electricity supply has a standard
frequency of 60 hertz.
region of electrical contact between two
Higher Heating Value
(HHV)- The maximum heating value of a
fuel sample, which includes the
calorific value of the fuel (bone dry)
and the latent heat of vaporization of
the water in the fuel. (See moisture
content and net (lower) heating value,
Discharge Lamp A lamp that consists of
a sealed arc tube inside a glass
envelope, or outer jacket. The inner arc
tube is filled with elements that emit
light when ionized by electric current.
A ballast is required to provide the
proper starting voltage and to regulate
current during operation.
Lamp A type of High-Intensity
Discharge (HID) lamp that uses sodium
under high pressure as the primary
light-producing element. These high
efficiency lights produce a golden white
color and are used for interior
industrial applications, such as in
warehouses and manufacturing, and for
security, street, and area lighting.
Hole The vacancy
where an electron would normally exist
in a solid; behaves like a positively
Home Energy Rating
Systems (HERS) A nationally recognized
energy rating program that gives
builders, mortgage lenders, secondary
lending markets, homeowners, sellers,
and buyers a precise evaluation of
energy losing deficiencies in homes.
Builders can use this system to gauge
the energy quality in their home and
also to have a star rating on their home
to compare to other similarly built
region between an n-layer and a p-layer
in a single material, photovoltaic cell.
Loop In this type of closed-loop
geothermal heat pump installation, the
fluid-filled plastic heat exchanger
pipes are laid out in a plane parallel
to the ground surface. The most common
layouts either use two pipes, one buried
at six feet, and the other at four feet,
or two pipes placed side-by-side at five
feet in the ground in a two-foot wide
trench. The trenches must be at least
four feet deep. Horizontal ground loops
are generally most cost-effective for
residential installations, particularly
for new construction where sufficient
land is available. Also see closed-loop
geothermal heat pump systems.
Turbines Turbines in which the axis of
the rotor's rotation is parallel to the
wind stream and the ground.
Horsepower (hp) A
unit of rate of operation. Electrical
hp: a measure of time rate of mechanical
energy output; usually applied to
electric motors as the maximum output; 1
electrical hp is equal to 0.746
kilowatts or 2,545 Btu per hour. Shaft
hp: a measure of the actual mechanical
energy per unit time delivered to a
turning shaft; 1 shaft Hp is equal to 1
electrical Hp or 550 foot pounds per
second. Boiler Hp: a measure to the
maximum rate to heat output of a steam
generator; 1 boiler Hp is equal to
33,480 Btu per hour steam output. A unit
for measuring the rate of work (or
power) equivalent to 33,000 footpounds
per minute or 746 watts.
Horsepower Hour (hph)
One horsepower provided over one hour;
equal to 0.745 kilowatt-hour or 2,545
Hot Air Furnace A
heating unit where heat is distributed
by means of convection or fans. Hot Dry
Rock A geothermal energy resource that
consists of high temperature rocks above
300 F (150 C) that may be fractured and
have little or no water. To extract the
heat, the rock must first be fractured,
then water is injected into the rock and
pumped out to extract the heat. In the
western United States, as much as 95,000
square miles (246,050 square km) have
hot dry rock potential.
Hot Water Heating
Systems (see hydronic)
House Subcommittee on
Energy and Environment This committee
has legislative jurisdiction and general
and special oversight and investigative
authority on all matters relating to
energy and environmental research and
development and demonstration.
House Water and Power
Committee This committee has oversight
over the generation and marketing of
electric power from federal water
projects by federally charted or Federal
RPM authorities, measures and matters
concerning water resources planning,
compacts relating to use and
apportionment of interstate waters,
water rights or power movement programs,
measures and matters pertaining to
irrigation and reclamation projects and
other water resources development
HOV High occupancy
Hub Height The
height above the ground that a
horizontal axis wind turbine's hub is
Humidifier A device
used to maintain a specified humidity in
a conditioned space.
Humidity A measure
of the moisture content of air; may be
expressed as absolute, mixing ratio,
saturation deficit, relative, or
ventilation and air conditioning
Hybrid System A
renewable energy system that includes
two different types of technologies that
produce the same type of energy; for
e.g., a wind turbine and a solar
photovoltaic array combined to meet a
Plant A power plant that produces
electricity by the force of water
falling through a hydro turbine that
spins a generator.
gas or some other source to generate
electricity during low water periods
when hydropower is scarce.
colorless, odorless, highly flammable
gaseous chemical element. It is the
lightest of all gases and the most
abundant element in the universe,
occurring chiefly in combination with
oxygen in water and also in acids,
bases, alcohols, petroleum, and other
hydrocarbons. It can be used as a fuel
since it has a very high energy content.
Amorphous Silicon Amorphous silicon
with a small amount of incorporated
hydrogen. The hydrogen neutralizes
dangling bonds in the amorphous silicon,
allowing charge carriers to flow more
Systems A type of heating system where
water is heated in a boiler and either
moves by natural convection or is pumped
to heat exchangers or radiators in
rooms; radiant floor systems have a grid
of tubing laid out in the floor for
distributing heat. The temperature in
each room is controlled by regulating
the flow of hot water through the
radiators or tubing.
that comes from moving water.
These fluids can be either water or
steam trapped in fractured or porous
rocks; they are found from several
hundred feet to several miles below the
Earth's surface. The temperatures vary
from about 90 F to 680 F (32 C to 360 C)
but roughly 2/3 range in temperature
from 150 F to 250 F (65.5 C to 121.1 C).
The latter are the easiest to access
and, therefore, the only forms being
Ignite To heat a
gaseous mixture to the temperature at
which combustion takes place.
Ignition Point The
minimum temperature at which combustion
of a solid or fluid can occur.
measure of the amount of light incident
on a surface; measured in foot-candles
Impoundment A body
of water confined by a dam, dike,
floodgate or other artificial barrier.
Impulse Turbine A
turbine that is driven by high velocity
jets of water or steam from a nozzle
directed to vanes or buckets attached to
a wheel. (A pelton wheel is an impulse
lights use an electrically heated
filament to produce light in a vacuum or
inert gas-filled bulb.
Bulb An incandescent bulb is a type of
electric light in which light is
produced by a filament heated by
electric current. The most common
example is the type you find in most
table and floor lamps. In commercial
buildings, incandescent lights are used
for display lights in retail stores,
hotels and motels. This includes the
very small, highintensity track lights
used to display merchandise or provide
spot illumination in restaurants.
Radiation The amount of solar
radiation striking a surface per unit of
time and area.
Producer A company or individual that
is not directly regulated as a power
provider. These entities produce power
for their own use and/or sell it to
regulated power providers.
Indirect Solar Gain
System A passive solar heating system
in which the sun warms a heat storage
element, and the heat is distributed to
the interior space by convection,
conduction, and radiation.
Indirect Solar Water
Heater These systems circulate fluids
other than water (such as diluted
antifreeze) through the collector. The
collected heat is transferred to the
household water supply using a heat
exchanger. Also known as "closed-loop"
process of producing an electrical or
magnetic effect through the influence of
a nearby magnet, electric current, or
electrically charged body.
A device that converts the mechanical
energy of rotation into electricity
based on electromagnetic induction. An
electric voltage (electromotive force)
is induced in a conducting loop (or
coil) when there is a change in the
number of magnetic field lines (or
magnetic flux) passing through the loop.
When the loop is closed by connecting
the ends through an external load, the
induced voltage will cause an electric
current to flow through the loop and
load. Thus rotational energy is
converted into electrical energy.
Induction Motor A
motor in which a three phase (or any
multiphase) alternating current (i.e.
the working current) is supplied to
iron-cored coils (or windings) within
the stator. As a result, a rotating
magnetic field is set up, which induces
a magnetizing current in the rotor coils
(or windings). Interaction of the
magnetic field produced in this manner
with the rotating field causes
rotational motion to occur.
Heat The thermal energy used in an
Industrial Sector (of
the Economy) The part of the economy
having to do with the production of
goods. The industrial sector is made up
of factories, power plants, etc.
Inert Gas A gas
that does not react with other
substances; e.g. argon or krypton;
sealed between two sheets of glazing to
decrease the U-value (increase the
R-Value) of windows.
Inertia A property
of matter by which it remains at rest or
in uniform motion in the same straight
line unless acted upon by some outside
Electromagnetic radiation whose
wavelengths lie in the range from 0.75
micrometer to 1000 micrometers;
invisible long wavelength radiation
(heat) capable of producing a thermal or
photovoltaic effect, though less
effective than visible light.
solar power density incident on a
surface of stated area and orientation,
usually expressed as Watts per square
meter or Btu per square foot per hour.
The total capacity of electrical
generation devices in a power station or
Efficiency (of a Solar Collector) The
amount of energy absorbed (or converted)
by a solar collector (or photovoltaic
cell or module) over a 15 minute period.
Materials that prevent or slow down the
movement of heat.
A pre-cut layer of insulation applied
around a water heater storage tank to
reduce stand-by heat loss from the tank.
Insulator A device
or material with a high resistance to
Storage System This simple passive
solar hot water system consists of one
or more storage tanks placed in an
insulated box that has a glazed side
facing the sun. An integral collector
storage system is mounted on the ground
or on the roof (make sure your roof
structure is strong enough to support
it). Some systems use "selective"
surfaces on the tank(s). These surfaces
absorb sun well but inhibit radiative
loss. Also known as bread box systems or
Systems A type of heating appliance
that performs more than one function,
for example space and water heating.
Plan (IRP) A plan developed by an
electric power provider, sometimes as
required by a public regulatory
commission or agency, that defines the
short and long term capacity additions
(supply side) and demand side management
programs that it will undertake to meet
projected energy demands.
connection or link between power systems
that enables them to draw on each
other's reserve capacity in time of
Generators Power plants, whose output
depends on a factor(s) that cannot be
controlled by the power generator
because they utilize intermittent
resources such as solar energy or the
Electric Power Plant The generation of
electric power by a heat engine which
converts part of the heat generated by
combustion of the fuel into mechanical
motion to operate an electric generator.
Internal Gain The
heat produced by sources of heat in a
building (occupants, appliances,
Materials with high thermal energy
storage capacity contained in or part of
a building's walls, floors, or
Internal Rate of
Return A widely used rate of return
for performing economic analysis. This
method solves for the interest rate that
equates the equivalent worth of an
alternative's cash receipts or savings
to the equivalent worth of cash
expenditures, including investments. The
resultant interest rate is termed the
internal rate of return (IRR).
Energy loads that can be shut off or
disconnected at the supplier's
discretion or as determined by a
contractual agreement between the
supplier and the customer.
Power that, by contract, can be
interrupted in the event of a power
Longdistance transmission lines such as
those connecting the Northwest with the
Intrinsic Layer A
layer of semiconductor material (as used
in a solar photovoltaic device) whose
properties are essentially those of the
pure, undoped, material.
Inverter A device
that converts direct current electricity
(from for example a solar photovoltaic
module or array) to alternating current
for use directly to operate appliances
or to supply power to a electricity
Investment Tax Credit
A tax credit granted for specific
types of investments.
Utility (IOU) A power provider owned
by stockholders or other investors;
sometimes referred to as a private power
provider, in contrast to a public power
provider that is owned by a government
agency or cooperative.
Ion An electrically
charged atom or group of atoms that has
lost or gained electrons; a loss makes
the resulting particle positively
charged; a gain makes the particle
Ionizer A device
that removes airborne particles from
breathable air. Negative ions are
produced and give up their negative
charge to the particles. These new
negative particles are then attracted to
the positive particles surrounding them.
This accumulation process continues
until the particles become heavy enough
to fall to the ground.
direct, diffuse, and reflected solar
radiation that strikes a surface.
Isolated Solar Gain
System A type of passive solar heating
system where heat is collected in one
area for use in another.
Surface Transportation Efficiency Act (a
A semiconductor material that is left
intrinsic, or undoped so that the
concentration of charge carriers is
characteristic of the material itself
rather than of added impurities.
I-V Curve A
graphical plot or representation the
current and voltage output of a solar
photovoltaic cell or module as a load on
the device is increased from short
circuit (no load) condition to the open
circuit condition; used to characterize
enclosure on a water heater, furnace, or
Joist A structural,
load-carrying building member with an
open web system that supports floors and
roofs utilizing wood or specific steels
and is designed as a simple span member.
Joule A metric unit
for measuring work and energy, named
after James Joule. It is equal to the
work done when a one ampere current is
passed through a resistance of one ohm
for one second. The energy produced by a
force of one Newton operating through a
distance of one meter; 1 Joule per
second equals 1 Watt or 0.737
foot-pounds; 1 Btu equals 1,055 Joules.
Joule's Law The
rate of heat production by a steady
current in any part of an electrical
circuit that is proportional to the
resistance and to the square of the
current, or, the internal energy of an
ideal gas depends only on its
Junction A region
of transition between semiconductor
layers, such as a p/n junction, which
goes from a region that has a high
concentration of acceptors (p-type) to
one that has a high concentration of
Kaplan Turbine A
type of turbine that has two blades
whose pitch is adjustable. The turbine
may have gates to control the angle of
the fluid flow into the blades.
Kerosene A thick
oil obtained from petroleum and used as
a fuel and solvent. A type of heating
fuel derived by refining crude oil that
has a boiling range at atmospheric
pressure from 400 degrees to 550 degrees
A unit of apparent power, equal to
1,000 volt-amperes; the mathematical
product of the volts and amperes in an
Kilowatt (kW) A
standard unit of electrical power equal
to one thousand watts, or to the energy
consumption at a rate of 1000 Joules per
second. A kilowatt equals 1000 watts.
A measure of electricity defined as a
unit of work or energy, measured as 1
kilowatt (1,000 watts) of power expended
for 1 hour. One kWh is equivalent to
3,412 Btu or 3.6 million joules.
Kinetic The energy
of a body which results from its motion.
Energy available as a result of motion
that varies directly in proportion to an
object's mass and the square of its
Kinetic Theory of
Energy The theory that the minute
particles of all matter are in constant
motion and that the temperature of a
substance depends upon the velocity
(speed) of the motion.
Kinetic Theory of
Gases The theory that physical
properties of a gas are due to the rapid
motion in a straight line of its
molecules, to their impacts against each
other and the walls of the container,
and to weak attraction forces between
Kneewall A wall
usually about 3 to 4 feet high located
that is placed in the attic of a home,
anchored with plates between the attic
floor joists and the roof joist.
Sheathing can be attached to these walls
to enclose an attic space.
wastewater treatment or livestock
facilities, a shallow pond used to store
wastewater where sunlight and biological
activity decompose the waste.
Lamp A light source
composed of a metal base, a glass tube
filled with an inert gas or a vapor, and
base pins to attach to a fixture.
Features and vegetation on the outside
of or surrounding a building for
aesthetics and energy conservation.
Langley A unit or
measure of solar radiation; 1 calorie
per square centimeter or 3.69 Btu per
Latent Cooling Load
The load created by moisture in the air,
including from outside air infiltration
and that from indoor sources such as
occupants, plants, cooking, showering,
Latent Heat The
change in heat content that occurs with
a change in phase and without change in
Latent Heat of
Vaporization The quantity of heat
produced to change a unit weight of a
liquid to vapor with no change in
Lattice The regular
periodic arrangement of atoms or
molecules in a crystal of semiconductor
Thermodynamics The first law states
that energy can not be created or
destroyed; the second law states that
when a free exchange of heat occurs
between two materials, the heat always
moves from the warmer to the cooler
Lead Acid Battery
An electrochemical battery that uses
lead and lead oxide for electrodes and
sulfuric acid for the electrolyte.
Leading Edge In
reference to a wind energy conversion
system, the area of a turbine blade
surface that first comes into contact
with the wind.
Related to stand-by power, leaking
electricity is the power needed for
electrical equipment to remain ready for
use while in a dormant mode or
operation. Electricity is still used by
many electrical devices, such as TVs,
stereos, and computers, even when you
think they are turned "off."
Evaluating all the possibilities for
meeting demand for energy services,
including the entire range of generating
sources available and conservation or
Lethe A measure of
air purity that is equal to one complete
air change (in an interior space).
Levelized Life Cycle
Cost A total life cycle cost divided
into equal amounts.
Life Cycle Cost The
sum of all the costs both recurring and
nonrecurring, related to a product,
structure, system, or service during its
life span or specified time period.
Lift The force that
pulls a wind turbine blade, as opposed
electromagnetic energy that an observer
Light Quality A
description of how well people in a
lighted space can see to do visual tasks
and how visually comfortable they feel
in that space.
Light Trapping The
trapping of light inside a semiconductor
material by refracting and reflecting
the light at critical angles; trapped
light will travel further in the
material, greatly increasing the
probability of absorption and hence of
producing charge carriers.
Defects, such as dangling bonds,
induced in an amorphous silicon
semiconductor upon initial exposure to
Line Loss (or Drop)
Electrical energy lost due to inherent
inefficiencies in an electrical
transmission and distribution system
under specific conditions.
Liquefied Natural Gas
(LNG) Natural gas that has been
liquefied by reducing its temperature to
minus 258 degrees Fahrenheit at
atmospheric pressure. LNG is kept in
special cryogenic tanks and often is
stored in great quantities for use in
distribution systems during periods of
high natural gas demand. It also has
been used as a vehicle fuel. One cubic
foot of LNG, when vaporized, equals
approximately 620 cubic feet of gas.
Gas (LPG) A group of hydrocarbonbased
gases derived from crude oil refining or
natural gas fractionation. They include
ethane, ethylene, propane, propylene,
normal butane, butylene, isobutane, and
isobutylene. For convenience of
transportation, these gases are
liquefied through pressurization.
Heating System A solar heating system
that uses a liquid as the heat transfer
Exchanger A heat exchanger that
transfers the heat contained in a liquid
heat transfer fluid to air.
Exchanger A heat exchanger that
transfers heat contained in a liquid
heat transfer fluid to another liquid.
Battery A battery that uses lithium in
the negative electrode and a metal
sulfide in the positive electrode, and
the electrolyte is molten salt; can
store large amounts of energy per unit
Live Steam Steam
available directly from a boiler under
Load The power and
energy requirements of users on the
electric power system in a certain area
or the amount of power delivered to a
certain point. The power required to run
a defined circuit or system, such as a
refrigerator, building, or an entire
electricity distribution system.
Assessing and quantifying the discrete
components that comprise a load. This
analysis often includes time of day or
season as a variable.
Load Duration Curve
A curve that displays load values on the
horizontal axis in descending order of
magnitude against the percent of time
(on the vertical axis) that the load
values are exceeded.
Load Factor The
ratio of average energy demand (load) to
maximum demand (peak load) during a
Load Forecast An
estimate of power demand at some future
Load Leveling The
deferment of certain loads to limit
electrical power demand, or the
production of energy during off-peak
periods for storage and use during peak
Load Management To
influence the demand on a power source.
Load Profile or Shape
A curve on a chart showing power (kW)
supplied (on the horizontal axis)
plotted against time of occurrence (on
the vertical axis) to illustrate the
variance in a load in a specified time
Turning off or disconnecting loads to
limit peak demand.
Load Shifting A
load management objective that moves
loads from on-peak periods to off-peak
Local Solar Time A
system of astronomical time in which the
sun crosses the true north-south
meridian at 12 noon, and which differs
from local time according to longitude,
time zone, and equation of time.
Log Law In
reference to a wind energy conversion
system, the wind speed profile in which
wind speeds increase with the
logarithmic of the height of the wind
turbine above the ground.
Long Ton A unit
that equals 20 long hundredweight or
2,240 pounds. Used mainly in England.
Longwall Mining An
automated form of underground coal
mining characterized by high recovery
and extraction rates, feasible only in
relatively flatlying, thick, and
uniform coal beds. A highpowered
cutting machine is passed across the
exposed face of coal, shearing away
broken coal, which is continuously
hauled away by a floorlevel conveyor
system. Longwall mining extracts all
machine minable coal between the floor
and ceiling within a contiguous block of
coal, known as a panel, leaving no
support pillars within the panel area.
Panel dimensions vary over time and with
mining conditions but currently average
about 900 feet wide (coal face width)
and more than 8,000 feet long (the
minable extent of the panel, measured in
direction of mining). Longwall mining is
done under movable roof supports that
are advanced as the bed is cut. The roof
in the minedout area is allowed to fall
as the mining advances.
Infrared or radiant heat.
construction of a second pipeline
parallel to an existing pipeline, thus
increasing the capacity of the system.
Loose Fill Insulation
Insulation made from rockwool fibers,
fiberglass, cellulose fiber, vermiculite
or perlite minerals, and composed of
loose fibers or granules can be applied
by pouring directly from the bag or with
Loss of Load
Probability (LOLP) A measure of the
probability that a system demand will
exceed capacity during a given period;
often expressed as the estimated number
of days over a long period, frequently
10 years or the life of the system.
Losses (Energy) A
general term applied to the energy that
is converted to a form that can not be
effectively used (lost) during the
operation of an energy producing,
conducting, or consuming system.
Low Btu Gas A fuel
gas with a heating value between 90 and
200 Btu per cubic foot.
Low Flush Toilet A
toilet that uses less water than a
standard one during flushing, for the
purpose of conserving water resources.
Low-E Coatings &
(Window) Films A coating applied to
the surface of the glazing of a window
to reduce heat transfer through the
Windows & (Window) Films
Energy-efficient windows that have a
coating or film applied to the surface
of the glass to reduce heat transfer
through the window.
Lower (Net) Heating
Value The lower or net heat of
combustion for a fuel that assumes that
all products of combustion are in a
gaseous state. (See Net Heating Value
Low-Flow Solar Water
Heating Systems The flow rate in these
systems is 1/8 to 1/5 the rate of most
solar water heating systems. The
low-flow systems take advantage of
stratification in the storage tank and
theoretically allows for the use of
smaller diameter piping to and from the
collector and a smaller pump.
Lamp A type of lamp that produces
light from sodium gas contained in a
bulb operating at a partial pressure of
0.13 to 1.3 Pascal. The yellow light and
large size make them applicable to
lighting streets and parking lots.
Lumen An empirical
measure of the quantity of light. It is
based upon the spectral sensitivity of
the photosensors in the human eye under
high (daytime) light levels.
Photometrically it is the luminous flux
emitted with a solid angle (1 steradian)
by a point source having a uniform
luminous intensity of 1 candela.
Lumens/Watt (lpw) A
measure of the efficacy (efficiency) of
lamps. It indicates the amount of light
(lumens) emitted by the lamp for each
unit of electrical power (Watts) used.
complete lighting unit consisting of a
lamp(s), housing, and connection to the
physical measure of the subjective
sensation of brightness; measured in
Lux The unit of
illuminance equivalent to 1lumen per
Magma Molten or
partially molten rock at temperatures
ranging from 1,260 F to 2,880 F (700 C
to 1600 C). Some magma bodies are
believed to exist at drillable depths
within the Earth's crust, although
practical technologies for harnessing
magma energy have not been developed. If
ever utilized, magma represents a
potentially enormous resource.
Magnet Any piece of
iron, steel, etc., that has the property
of attracting iron or steel.
Magnetic Ballast A
type of florescent light ballast that
uses a magnetic core to regulate the
voltage of a florescent lamp.
Main A distribution
line that serves as a common source of
supply for more than one service line.
Main Extension The
addition of pipe to an existing main to
serve new customers.
Make-Up Air Air
brought into a building from outside to
replace exhaust air.
Manual J The
standard method for calculating
residential cooling loads developed by
the Air-Conditioning and Refrigeration
Institute (ARI) and the Air Conditioning
Contractors of America (ACCA) based
largely on the American Society of
Heating, Refrigeration, and
Air-Conditioning Engineer's (ASHRAE)
"Handbook of Fundamentals."
Marginal Cost The
cost of producing one additional unit of
such as brick, rock, or stone.
Masonry Stove A
type of heating appliance similar to a
fireplace, but much more efficient and
clean burning. They are made of masonry
and have long channels through which
combustion gases give up their heat to
the heavy mass of the stove, which
releases the heat slowly into a room.
Often called Russian or Finnish
Mass Burn Facility
A type of municipal solid waste (MSW)
incineration facility in which MSW is
burned with only minor presorting to
remove oversize, hazardous, or explosive
materials. Mass burn facilities can be
large, with capacities of 3000 tons (2.7
million kg) of MSW per day or more. They
can be scaled down to handle the waste
from smaller communities, and modular
plants with capacities as low as 25 tons
(22.7 thousand kg) per day have been
built. Mass burn technologies represent
over 75% of all the MSW-to-energy
facilities constructed in the United
States to date. The major components of
a mass burn facility include refuse
receiving and handling, combustion and
steam generation, flue gas cleaning,
power generation (optional), condenser
cooling water, residue ash hauling and
Mcf An abbreviation
for one thousand cubic feet of natural
gas with a heat content of 1,000,000
Btus, or 10 therms.
Mean Power Output (of
a Wind Turbine) The average power
output of a wind energy conversion
system at a given mean wind speed based
on a Raleigh frequency distribution.
Mean Wind Speed The
arithmetic wind speed over a specified
time period and height above the ground
(the majority of U.S. National Weather
Service anemometers are at 20 feet (6.1
The energy of motion used to perform
The power produced by motion.
Those elements of building used to
control the interior climate.
Median Wind Speed
The wind speed with 50 percent
probability of occurring.
Medium Btu Gas Fuel
gas with a heating value of between 200
and 300 Btu per cubic foot.
Medium Pressure For
valves and fittings, implies that they
are suitable for working pressures
between 125 to 175 pounds per square
thousand kilowatts, or 1 million watts;
standard measure of electric power plant
thousand kilowatt-hours or 1 million
organic chemical compound that has a
sulfur like odor that is added to
natural gas before distribution to the
consumer, to give it a distinct,
unpleasant odor (smells like rotten
eggs). This serves as a safety device by
allowing it to be detected in the
atmosphere, in cases where leaks occur.
Mercury Vapor Lamp- A
high-intensity discharge lamp that uses
mercury as the primary light-producing
element. Includes clear, phosphor
coated, and self-ballasted lamps.
Met An approximate
unit of heat produced by a resting
person, equal to about 18.5 Btu per
square foot per hour.
Metal Halide Lamp A
high-intensity discharge lamp type that
uses mercury and several halide
additives as light-producing elements.
These lights have the best Color
Rendition Index (CRI) of the
High-Intensity Discharge lamps. They can
be used for commercial interior lighting
or for stadium lights.
Methane (CH4) A
colorless, tasteless, highly flammable,
odorless hydrocarbon gas composed of one
molecule of Carbon and four of hydrogen.
It is the major component of natural
gas. It is also an important source of
hydrogen in various industrial
processes. Methane is a greenhouse gas.
It is the main constituent of "natural
gas" that is formed naturally by
methanogenic, anaerobic bacteria or can
be manufactured, and which is used as a
fuel and for manufacturing chemicals.
Methyl alcohol or wood alcohol) A
clear, colorless, very mobile liquid
that is flammable and poisonous; used as
a fuel and fuel additive, and to produce
Metric Ton (Tonne)
A unit of mass equal to 1,000 kilograms
or 2,204.6 pounds.
local climate of specific place or
habitat, as influenced by landscape
Microgroove A small
groove scribed into the surface of a
solar photovoltaic cell which is filled
with metal for contacts.
millionth of a meter (10-6 m).
Miles Per Gallon
(MPG) A measure of vehicle fuel
efficiency. MPG is computed as the ratio
of the total number of miles traveled by
a vehicle to the total number of gallons
Mill A common
monetary measure equal to one-thousandth
of a dollar or a tenth of a cent.
Minority Carrier A
current carrier, either an electron or a
hole, that is in the minority in a
specific layer of a semiconductor
material; the diffusion of minority
carriers under the action of the cell
junction voltage is the current in a
Lifetime The average time a minority
carrier exists before recombination.
Mixing Valve A
valve operated by a thermostat that can
be installed in solar water heating
systems to mix cold water with water
from the collector loop to maintain a
safe water temperature.
MMcf One million
standard cubic feet of gas.
Method A method used to estimate
building heating loads by assuming that
heat loss and gain is proportional to
the equivalent heat-loss coefficient for
the building envelope.
Module The smallest
protected structure housing
interconnected photovoltaic cells and
providing a single dc electrical output;
also called a panel.
The water content of a substance (a
solid fuel) as measured under specified
conditions being the: Dry Basis, which
equals the weight of the wet sample
minus the weight of a (bone) dry sample
divided by the weight of the dry sample
times 100 (to get percent); Wet Basis,
which is equal to the weight of the wet
sample minus the weight of the dry
sample divided by the weight of the wet
sample times 100.
The process of controlling indoor
moisture levels and condensation.
that normally consist of two or more
atoms joined together. An example is a
water molecule that is made up of two
hydrogen atoms and one oxygen atom.
planting, cultivation, and harvesting of
a single species of crop in a specified
Fabricated as a single structure.
Motor A machine
supplied with external energy that is
converted into force and/or motion.
Motor Speed The
number of revolutions that the motor
turns in a given time period (i.e.
revolutions per minute, rpm).
A device that reduces heat loss at night
and during cloudy periods and heat gain
during the day in warm weather. A
movable insulator could be an insulative
shade, shutter panel, or curtain.
Tertiary Butyl Ether (MTBE) is an ether
compound used as a gasoline blending
component to raise the oxygen content of
gasoline. MTBE is made by combining
isobutylene (from various refining and
chemical processes) and methanol
(usually made from natural gas).
Apartment building and condominiums.
A high-efficiency photovoltaic device
containing two or more cell junctions,
each of which is optimized for a
particular part of the solar spectrum.
Multi-Zone System A
building heating, ventilation, and/or
air conditioning system that distributes
conditioned air to individual zones or
Municipal Solid Waste
(MSW) Residential solid waste and some
nonhazardous commercial, institutional,
and industrial wastes.
Municipal Waste As
defined in the Energy Security Act (P.L.
96-294; 1980) as "any organic matter,
including sewage, sewage sludge, and
industrial or commercial waste, and
mixtures of such matter and inorganic
refuse from any publicly or privately
operated municipal waste collection or
similar disposal system, or from similar
waste flows (other than such flows which
constitute agricultural wastes or
residues, or wood wastes or residues
from wood harvesting activities or
production of forest products)."
Municipal Waste to
Energy Project (or Plant) A facility
that produces fuel or energy from
municipal solid waste.
Nacelle The cover
for the gear box, drive train,
generator, and other components of a
Name Plate A metal
tag attached to a machine or appliance
that contains information such as brand
name, serial number, voltage, power
ratings under specified conditions, and
other manufacturer supplied data.
Code (NEC) The NEC is a set of
regulations that have contributed to
making the electrical systems in the
United States one of the safest in the
world. The intent of the NEC is to
ensure safe electrical systems are
designed and installed. The National
Fire Protection Association has
sponsored the NEC since 1911. The NEC
changes as technology evolves and
component sophistication increases. The
NEC is updated every three years.
Following the NEC is required in most
Policy Act of 1992 The culmination of
several years of effort to define a
national energy strategy, signed into
law by President Bush in 1992.
Electric Cooperative Association (NRECA)
This is a national organization
dedicated to representing the interests
of cooperative electric power providers
and the consumers they serve. Members
come from the 46 states that have an
electric distribution cooperative.
Space cooling achieved by shading,
natural (unassisted, as opposed to
forced) ventilation, conduction control,
radiation, and evaporation; also called
Natural Draft Draft
that is caused by temperature
differences in the air.
Natural Gas A
colorless, odorless, nontoxic gas that
is found in porous geologic formations
beneath the earths surface, often in
association with petroleum. It consists
mostly of methane (CH4), with minor
amounts of ethane, propane and nitrogen.
Natural gas is lighter than air and when
burned, produces only heat, carbon
dioxide and water vapor.
Distribution Company A company that
obtains the major portion of its gas
operating revenues from the operation of
a retail gas distribution system, and
which operates no transmission system
other than incidental connections within
its own system or to the system of
another company. Also known as a local
distribution company (LDC).
Natural Gas Hydrates
Solid, crystalline, waxlike
substances composed of water, methane,
and usually a small amount of other
gases, with the gases being trapped in
the interstices of a waterice lattice.
They form beneath permafrost and on the
ocean floor under conditions of
moderately high pressure and at
temperatures near the freezing point of
Natural Gas Liquids
(NGL) Substances that can be processed
as liquids out of natural gas by
absorption or condensation.
Natural Gas Steam
Reforming Production A two step
process where in the first step natural
gas is exposed to a high-temperature
steam to produce hydrogen, carbon
monoxide, and carbon dioxide. The second
step is to convert the carbon monoxide
with steam to produce additional
hydrogen and carbon dioxide.
Natural Gas Vehicle
(NGV) A vehicle that runs on
compressed or liquefied natural gas.
Often they are equipped to operate on
either compressed natural gas or
Ventilation that is created by the
differences in the distribution of air
pressures around a building. Air moves
from areas of high pressure to areas of
low pressure with gravity and wind
pressure affecting the airflow. The
placement and control of doors and
windows alters natural ventilation
Net (Lower) Heating
Value (NHV) The potential energy
available in a fuel as received, taking
into account the energy loss in
evaporating and superheating the water
in the fuel. Equal to the higher heating
value minus 1050W where W is the weight
of the water formed from the hydrogen in
the fuel, and 1050 is the latent heat of
vaporization of water, in Btu, at 77
Net Energy Production
(or Balance) The amount of useful
energy produced by a system less the
amount of energy required to produce the
Equal to gross generation less
electricity consumption of a power
Net Metering The
practice of using a single meter to
measure consumption and generation of
electricity by a small generation
facility (such as a house with a wind or
solar photovoltaic system). The net
energy produced or consumed is purchased
from or sold to the power provider,
Net Present Value
The value of a personal portfolio,
product, or investment after
depreciation and interest on debt
capital are subtracted from operating
income. It can also be thought of as the
equivalent worth of all cash flows
relative to a base point called the
This compound of nitrogen and oxygen is
formed by the oxidation of nitric oxide
(NO) which is produced by the combustion
of solid fuels.
Nitrogen Oxides (NOx)
The products of all combustion
processes formed by the combination of
nitrogen and oxygen.
The effect of cooling by the radiation
of heat from a building to the night
The approximate energy producing
capacity of a power plant, under
specified conditions, usually during
periods of highest load.
Nominal Price The
price paid for goods or services at the
time of a transaction; a price that has
not been adjusted to account for
System A type of solar energy system
that does not rely on special devices to
concentrate the sun's radiation while
Fuels that cannot be easily made or
"renewed." We can use up nonrenewable
fuels. Oil, natural gas, and coal are
Generator/Power Producer A class of
power generator that is not a regulated
power provider and that has generating
plants for the purpose of supplying
electric power required in the conduct
of their industrial and commercial
Capacity A characteristic applied to
domestic water heaters that is the
amount of gallons raised 100 degrees
Fahrenheit per hour (or minute) under a
specified thermal efficiency.
Planning Council Comprised of
governorappointed representatives from
Idaho, Montana, Oregon and Washington,
the Council is a planning and
policymaking body charged with
developing an electric power plan that
will guarantee adequate and reliable
energy at the lowest cost to the
Northwest. It also is charged with
developing a program to protect and
rebuild the fish and wildlife
populations in the Columbia River Basin
that have been affected by hydroelectric
development; and to conduct and
extensive program to involve the public
in the decisionmaking process.
A semiconductor produced by doping an
intrinsic semiconductor with an
electron-donor impurity (e.g.,
phosphorous in silicon).
Energy that comes from splitting atoms
of radioactive materials, such as
uranium, and which produces radioactive
Occupancy Sensor An
optical, ultrasonic, or infrared sensor
that turns room lights on when they
detect a person's presence and off after
the space is vacated.
Occupied Space The
space within a building or structure
that is normally occupied by people, and
that may be conditioned (heated, cooled
Ocean Energy Systems
Energy conversion technologies that
harness the energy in tides, waves, and
thermal gradients in the oceans.
Ocean Thermal Energy
Conversion (OTEC) The process or
technologies for producing energy by
harnessing the temperature differences
(thermal gradients) between ocean
surface waters and that of ocean depths.
Warm surface water is pumped through an
evaporator containing a working fluid in
a closed Rankine-cycle system. The
vaporized fluid drives a
turbine/generator. Cold water from deep
below the surface is used to condense
the working fluid. Open-Cycle OTEC
technologies use ocean water itself as
the working fluid. Closed-Cycle OTEC
systems circulate a working fluid in a
closed loop. A working 10 kilowatt,
closed-cycle prototype was developed by
the Pacific International Center for
High Technology Research in Hawaii with
U.s. Department of Energy funding, but
was not commercialized.
Off-Peak The period
of low energy demand, as opposed to
maximum, or peak, demand.
geographic area that lies seaward of the
coastline. In general, the coastline is
the line of ordinary low water along
with that portion of the coast that is
in direct contact with the open sea or
the line marking the seaward limit of
Offshore Reserves and
Production Unless otherwise dedicated,
energy source reserves and production
that are in either state or Federal
domains, located seaward of the
Sale of natural gas by an interstate
pipeline to a new customer outside its
traditional service area.
Ohm The unit of
resistance to the flow of an electric
Ohms A measure of
the electrical resistance of a material
equal to the resistance of a circuit in
which the potential difference of 1 volt
produces a current of 1 ampere.
Ohm's Law In a
given electrical circuit, the amount of
current in amperes (i) is equal to the
pressure in volts (V) divided by the
resistance, in ohms (R).
Oil The raw
material that petroleum products are
made from. A black liquid fossil fuel
found deep in the Earth. Gasoline and
most plastics are made from oil.
Oil (fuel) A
product of crude oil that is used for
space heating, diesel engines, and
One Sun The maximum
value of natural solar insolation.
One-Axis Tracking A
system capable of rotating about one
Energy supplied during periods of
relatively high system demands as
specified by the supplier.
Generation of energy at the location
where all or most of it will be used.
OnSystem Sale A
sale of natural gas by an interstate
pipeline to an existing customer within
its traditional service area.
Organization of Petroleum Exporting
Countries organized for the purpose of
negotiating with oil companies on
matters of oil production, prices, and
future concession rights. Current
members (as of the date of writing this
definition) are Algeria, Indonesia,
Iran, Iraq, Kuwait, Libya, Nigeria,
Qatar, Saudi Arabia, the United Arab
Emirates, and Venezuela. See OPEC's site
at http//www.opec.org for more
Open Access The
ability to send or wheel electric power
to a customer over a transmission and
distribution system that is not owned by
the power generator (seller).
The maximum possible voltage across a
photovoltaic cell; the voltage across
the cell in sunlight when no current is
Heat Pump System Open-loop (also known
as "direct") systems circulate water
drawn from a ground or surface water
source. Once the heat has been
transferred into or out of the water,
the water is returned to a well or
surface discharge (instead of being
recirculated through the system). This
option is practical where there is an
adequate supply of relatively clean
water, and all local codes and
regulations regarding groundwater
discharge are met.
Operating Cycle The
processes that a work input/output
system undergoes and in which the
initial and final states are identical.
Organic Waste Waste
material of animal or plant origin.
alignment of a building along a given
axis to face a specific geographical
direction. The alignment of a solar
collector, in number of degrees east or
west of true south.
discontinuance of electric power supply.
Shelf Offshore Federal domain.
process by which materials expel or
Outside Air Air
that is taken from the outdoors.
Outside Coil The
heat-transfer (exchanger) component of a
heat pump, located outdoors, from which
heat is collected in the heating mode,
or expelled in the cooling mode.
Overhang A building
element that shades windows, walls, and
doors from direct solar radiation and
protects these elements from
Overload To exceed
the design capacity of a device.
Ovonic A device
that converts heat or sunlight directly
to electricity, invented by Standford
Ovshinsky, that has a unique glass
composition that changes from an
electrically non-conducting state to a
fuel additives such as ethanol, ETBE, or
MTBE that add extra oxygen to gasoline
to reduce carbon monoxide pollution
produced by vehicles.
P/N A semiconductor
(photovoltaic) device structure in which
the junction is formed between a p-type
layer and an n-type layer.
Packing Factor The
ratio of solar collector array area to
actual land area.
Pane (Window) The
area of glass that fits in the window
Panel (Solar) A
term generally applied to individual
solar collectors, and typically to solar
photovoltaic collectors or modules.
Panel Radiator A
mainly flat surface for transmitting
drag-type wind machine that can react to
wind from any direction.
Reflector Lamp A type of lamp having a
lens of heavy durable glass that focuses
the light. They have longer lifetimes
with less lumen depreciation than
standard incandescent lamps.
Parabolic Dish A
solar energy conversion device that has
a bowl shaped dish covered with a highly
reflective surface that tracks the sun
and concentrates sunlight on a fixed
absorber, thereby achieving high
temperatures, for process heating or to
operate a heat (Stirling) engine to
produce power or electricity.
Parabolic Trough A
solar energy conversion device that uses
a trough covered with a highly
reflective surface to focus sunlight
onto a linear absorber containing a
working fluid that can be used for
medium temperature space or process heat
or to operate a steam turbine for power
or electricity generation.
Parabolic Trough A
type of solar concentrator collector
that has a linear parabolic shaped
reflector that focuses the suns
radiation on a receiver at the focus of
configuration of an electrical circuit
in which the voltage is the same across
the terminals. The positive reference
direction for each resistor current is
down through the resistor with the same
voltage across each resistor.
A way of joining photovoltaic cells or
modules by connecting positive leads
together and negative leads together;
such a configuration increases the
current, but not the voltage.
fine liquid or solid particles contained
in combustion gases. The quantity and
size of particulates emitted by cars,
power and industrial plants, wood
stoves, etc are regulated by the U.S.
Environmental Protection Agency.
chemical reaction that eliminates the
detrimental effect of electrically
reactive atoms on a photovoltaic cell's
System A means of capturing, storing,
and using heat from the sun.
(Building) Design A building design
that uses structural elements of a
building to heat and cool a building,
without the use of mechanical equipment,
which requires careful consideration of
the local climate and solar energy
resource, building orientation, and
landscape features, to name a few. The
principal elements include proper
building orientation, proper window
sizing and placement and design of
window overhangs to reduce summer heat
gain and ensure winter heat gain, and
proper sizing of thermal energy storage
mass (for example a Trombe wall or
masonry tiles). The heat is distributed
primarily by natural convection and
radiation, though fans can also be used
to circulate room air or ensure proper
Passive Solar Heater
A solar water or space-heating system
in which solar energy is collected,
and/or moved by natural convection
without using pumps or fans. Passive
systems are typically integral
collector/storage (ICS; or batch
collectors) or thermosyphon systems. The
major advantage of these systems is that
they do not use controls, pumps,
sensors, or other mechanical parts, so
little or no maintenance is required
over the lifetime of the system.
Passive Solar Home
A house built using passive solar design
Cooling To allow or augment the
natural movement of cooler air from
exterior, shaded areas of a building
through or around a building.
Payback Period The
amount of time required before the
savings resulting from your system equal
the system cost.
The process of implementing measures
to reduce peak power demands on a
The maximum energy demand or load in a
specified time period.
Peak Load Plant A
plant usually housing old,
lowefficiency steam units, gas
turbines, diesels, or pumpedstorage
hydroelectric equipment normally used
during the peakload periods.
Peak Power Power
generated that operates at a very low
capacity factor; generally used to meet
short-lived and variable high demand
Peak Shifting The
process of moving existing loads to
Peak Sun Hours The
equivalent number of hours per day when
solar irradiance averages 1 kW/m2. For
example, six peak sun hours means that
the energy received during total
daylight hours equals the energy that
would have been received had the
irradiance for six hours been 1 kW/m2.
Peak Watt A unit
used to rate the performance of a solar
photovoltaic (PV) cells, modules, or
arrays; the maximum nominal output of a
PV device, in Watts (Wp) under
standardized test conditions, usually
1000 Watts per square meter of sunlight
with other conditions, such as
Peak Wind Speed The
maximum instantaneous wind speed (or
velocity) that occurs within a specific
period of time or interval.
Power generation equipment or system
capacity to meet peak power demands.
A hydropower plant that is operated at
maximum allowable capacity for part of
the day and is either shut down for the
remainder of the time or operated at
minimal capacity level.
Pellet Stove A
space heating device that burns pellets;
are more efficient, clean burning, and
easier to operate relative to
conventional cord wood burning
Pellets Solid fuels
made from primarily wood sawdust that is
compacted under high pressure to form
small (about the size of rabbit feed)
pellets for use in a pellet stove.
Pelton Turbine A
type of impulse hydropower turbine where
water passes through nozzles and strikes
cups arranged on the periphery of a
runner, or wheel, which causes the
runner to rotate, producing mechanical
energy. The runner is fixed on a shaft,
and the rotational motion of the turbine
is transmitted by the shaft to a
generator. Generally used for high head,
low flow applications.
component of a hydropower plant. A
large pipe which carries moving water
from the reservoir to a turbine
generator in a hydropower plant.
Tracer Gas Technique (PFT) An air
infiltration measurement technique
developed by the Brookhaven National
Laboratory to measure changes over time
(one week to five months) when
determining a building's air
infiltration rate. This test cannot
locate exact points of infiltration, but
it does reveal long-term infiltration
Solar collector thermal performance
ratings based on collector efficiencies,
usually expressed in Btu per hour for
solar collectors under standard test or
operating conditions for solar radiation
intensity, inlet working fluid
temperatures, and ambient temperatures.
Perimeter Heating A
term applied to warm-air heating systems
that deliver heated air to rooms by
means of registers or baseboards located
along exterior walls.
Table of all known elements in a
Permeance A unit of
measurement for the ability of a
material to retard the diffusion of
water vapor at 73.4 F (23 C). A perm,
short for permeance, is the number of
grains of water vapor that pass through
a square foot of material per hour at a
differential vapor pressure equal to one
inch of mercury.
Organic and inorganic petroleum
compounds and mixtures that include but
are not limited to organic chemicals,
cyclic intermediates, plastics and
resins, synthetic fibers, elastomers,
organic dyes, organic pigments,
detergents, surface active agents,
carbon black, and ammonia.
refers to crude oil or the refined
products obtained from the processing of
crude oil (gasoline, diesel fuel,
heating oil, etc.) Petroleum also
includes lease condensate, unfinished
oils, and natural gas plant liquids.
Phantom Load Any
appliance that consumes power even when
it is turned off. Examples of phantom
loads include appliances with electronic
clocks or timers, appliances with remote
controls, and appliances with wall cubes
(a small box that plugs into an AC
outlet to power appliances).
current is carried by conductors and a
ground to residential, commercial, or
industrial consumers. The waveform of
the phase power appears as a single
continuous sine wave at the system
frequency whose amplitude is the rated
voltage of the power.
Phase Change The
process of changing from one physical
state (solid, liquid, or gas) to
another, with a necessary or
coincidental input or release of energy.
A material that can be used to store
thermal energy as latent heat. Various
types of materials have been and are
being investigated such as inorganic
salts, eutectic compounds, and paraffins,
for a variety of applications, including
solar energy storage (solar energy heats
and melts the material during the day
and at night it releases the stored heat
and reverts to a solid state).
Hydrogen Production A hydrogen
production process that process uses
algae. Under certain conditions, the
pigments in certain types of algae
absorb solar energy. An enzyme in the
cell acts as a catalyst to split water
molecules. Some of the bacteria produces
hydrogen after they grow on a substrate.
electric current induced by radiant
A device for measuring light intensity
that works by converting light falling
on, or reach it, to electricity, and
then measuring the current; used in
Cell A type of photovoltaic device in
which the electricity induced in the
cell is used immediately within the cell
to produce a chemical, such as hydrogen,
which can then be withdrawn for use.
Hydrogen Production The production of
hydrogen using a photoelectrochemical
Processes The production of electrical
current from light.
Photon A particle
of light that acts as an individual unit
process by which green plants make food
(carbohydrates) from water and carbon
dioxide, using the energy in sunlight.
(Conversion) Efficiency The ratio of
the electric power produced by a
photovoltaic device to the power of the
sunlight incident on the device.
Solar) Array A group of solar
photovoltaic modules connected together.
Cell Treated semiconductor material
that converts solar irradiance to
Module or Panel A solar photovoltaic
product that generally consists of
groups of PV cells electrically
connected together to produce a
specified power output under standard
test conditions, mounted on a substrate,
sealed with an encapsulant, and covered
with a protective glazing. Maybe further
mounted on an aluminum frame. A junction
box, on the back or underside of the
module is used to allow for connecting
the module circuit conductors to
System A complete PV power system
composed of the module (or array), and
balance-of-system (BOS) components
including the array supports, electrical
conductors/wiring, fuses, safety
disconnects, and grounds, charge
controllers, inverters, battery storage,
A device, usually made from silicon,
which converts some of the energy from
light (radiant energy) into electrical
energy. Another name for a solar cell.
Conversion The process by which
radiant (light) energy is changed into
A solid-state electrical device that
converts light directly into direct
current electricity of voltage-current
characteristics that are a function of
the characteristics of the light source
and the materials in and design of the
device. Solar photovoltaic devices are
made of various semi-conductor materials
including silicon, cadmium sulfide,
cadmium telluride, and gallium arsenide,
and in single crystalline,
multi-crystalline, or amorphous forms.
Watt see Peak Watt.
(PV/T) Systems A solar energy system
that produces electricity with a PV
module, and collects thermal energy from
the module for heating. There are no
commercially available systems available
(as of 11/97).
Deposition A method of depositing thin
semiconductor photovoltaic) films. With
this method, physical processes, such as
thermal evaporation or bombardment of
ions, are used to deposit elemental
semiconductor material on a substrate.
semiconductor (photovoltaic) device
structure that layers an intrinsic
semiconductor between a p-type
semiconductor and an n-type
semiconductor; this structure is most
often used with amorphous silicon PV
Pipeline (1) An
entity engaged in the sale and/or
transportation of natural gas in
interstate or intrastate commerce. In
this glossary, pipeline usually
denotes an interstate pipeline regulated
by FERC; (2) All parts of those physical
facilities through which gas is moved in
transportation, including pipe, valves
and other appurtenance attached to the
pipe, compressor units, metering
stations, regulator stations, delivery
stations and fabricated assemblies.
The maximum quantity of gas that can be
moved through a pipeline system at any
given time based on existing service
conditions such as available horsepower,
pipeline diameters, maintenance
schedules, regional demand for natural
gas, ambient temperatures, etc.
Distribution A pipeline that conveys
gas from a transmission pipeline to its
Pitch Control A
method of controlling a wind turbine's
speed by varying the orientation, or
pitch, of the blades, and thereby
altering its aerodynamics and
hightemperature, ionized gas composed
of electrons and positive ions in such
number that it is electrically neutral.
Plenum The space
between a hanging ceiling and the floor
above or roof; usually contains HVAC
ducts, electrical wiring, fire
suppression system piping, etc.
Plug Flow Digester
A type of anaerobic digester that has a
horizontal tank in which a constant
volume of material is added and forces
material in the tank to move through the
tank and be digested.
A high efficiency silicon photovoltaic
concentrator cell that employs light
trapping techniques and point-diffused
contacts on the rear surface for current
semiconductor (photovoltaic) material
composed of variously oriented, small,
registered trademark for plastic
sheeting material that can be used as a
vapor retarder. This plastic is used to
make grocery bags. It is a long chain of
carbon atoms with 2 hydrogen atoms
attached to each carbon atom.
Polystyrene (see Foam
Porous Media A
solid that contains pores; normally, it
refers to interconnected pores that can
transmit the flow of fluids. (The term
refers to the aquifer geology when
discussing sites for CAES.)
The requirement that an electric power
provider generate or purchase a
specified percentage of the power it
supplies/sells from renewable energy
resources, and thereby guarantee a
market for electricity generated from
renewable energy resources.
Potable Water Water
that is suitable for drinking, as
defined by local health officials.
Energy available due to position.
Pound of Steam One
pound of water in vapor phase; is NOT
steam pressure, which is expressed as
pounds per square inch (psi).
Pound Per Square Inch
Absolute (psia) A unit of pressure
[hydraulic (liquid) or pneumatic (gas)]
that does not include atmospheric
Power Energy that
is capable or available for doing work;
the time rate at which work is
performed, measured in horsepower,
Watts, or Btu per hour. Electric power
is the product of electric current and
Power The rate at
which energy is transferred. Electrical
energy is usually measured in watts.
Also used for a measurement of capacity.
Power (Output) Curve
A plot of a wind energy conversion
device's power output versus wind speed.
Power (Solar) Tower
A term used to describe solar thermal,
central receiver, power systems, where
an array of reflectors focus sunlight
onto a central receiver and absorber
mounted on a tower.
The ratio of power produced by a wind
energy conversion device to the power in
a reference area of the free windstream.
The process of modifying the
characteristics of electrical power (for
e.g., inverting dc to ac).
The loss of power when electricity is
sent over long distances.
Power Density The
amount of power per unit area of a free
Power Factor (PF)
The ratio of actual power being used in
a circuit, expressed in watts or
kilowatts, to the power that is
apparently being drawn from a power
source, expressed in volt-amperes or
Power Generation Mix
The proportion of electricity
distributed by a power provider that is
generated from available sources such as
coal, natural gas, petroleum, nuclear,
hydropower, wind, or geothermal.
Power Plant A
facility where power, especially
electricity, is generated.
Power Provider A
company or other organizational unit
that sells and distributes electrical
power (e.g., private or public
electrical utility), either to other
distribution and wholesale businesses or
to end-users. Sometimes power providers
also generate the power they sell.
Line An electrical conductor/cable
that carries electricity from a
generator to other locations for
Efficiency The percentage of the total
energy content of a power plants fuel
which is converted into electric energy.
The remaining energy is lost to the
environment as heat.
Preheater (Solar) A
solar heating system that preheats water
or air that is then heated more by
another heating appliance.
Present Value The
amount of money required to secure a
specified cash flow at a future date at
a specified return.
Pressure Drop The
loss in static pressure of a fluid
(liquid or gas) in a system due to
friction from obstructions in pipes,
from valves, fittings, regulators,
burners, etc, or by a breech or rupture
of the system.
Testing A technique used by energy
auditors, using a blower door, to locate
areas of air infiltration by
exaggerating the defects in the building
shell. This test only measures air
infiltration at the time of the test. It
does not take into account changes in
atmospheric pressure, weather, wind
velocity, or any activities the
occupants conduct that may affect air
infiltration rates over a period of
Reactor A reactor in which water,
heated by nuclear energy, is kept a high
pressure to prevent the water from
boiling. Steam is then generated in a
secondary coolant loop.
Primary Air The air
that is supplied to the combustion
chamber of a furnace.
Prime Mover Any
machine capable of producing power to do
work. The engine, turbine, water wheel,
or similar machine that drives an
electric generator; or, for reporting
purposes, a device that converts energy
to electricity directly (i.e.
photovoltaic solar and fuel cells).
Thermal energy that is used in
agricultural and industrial operations.
Producer Gas Low or
medium Btu content gas, composed mainly
of carbon monoxide, nitrogen(2), and
hydrogen(2) made by the gasification of
wood or coal.
Production, Oil and
Gas The lifting of oil and gas to the
surface and gathering, treating, field
processing (as in the case of processing
gas to extract liquid hydrocarbons), and
Combustion The elements and compounds
that result from the combustion of a
Thermostat A type of thermostat that
allows the user to program into the
devices' memory a pre-set schedule of
times (when certain temperatures occur)
to turn on HVAC equipment.
Projected Area The
net south-facing glazing area projected
on a vertical plane. Also, the solid
area covered at any instant by a wind
turbine's blades from the perspective of
the direction of the windstream (as
opposed to the swept area).
hydrocarbon gas, C3H8, occurring in
crude oil, natural gas, and refinery
cracking gas. It is used as a fuel, a
solvent, and a refrigerant. Propane
liquefies under pressure and is the
major component of liquefied petroleum
Propane (C3H8) A
normally gaseous straightchain
hydrocarbon. It is a colorless
paraffinic gas that boils at a
temperature of 43.67 degrees
Fahrenheit. It is extracted from natural
gas or refinery gas streams.
Turbine A turbine that has a runner
with attached blades similar to a
propeller used to drive a ship. As water
passes over the curved propeller blades,
it causes rotation of the shaft.
A commonly used analysis for reporting
fuel properties; may be on a dry
(moisture free) basis, as "fired", or on
an ash and moisture free basis.
Fractions usually reported include:
volatile matter, fixed carbon, moisture,
ash, and heating value (higher heating
Psi Pounds of
pressure per square inch.
per square inch absolute.
per square inch gauge.
instrument for measuring relative
humidity by means of wet and dry-bulb
analysis of atmospheric conditions,
particularly moisture in the air.
A semiconductor in which holes carry
the current; produced by doping an
intrinsic semiconductor with an electron
acceptor impurity (e.g., boron in
Regulatory Policy Act (PURPA) of 1978
A law that requires electric utilities
to purchase electricity produced from
qualifying power producers that use
renewable energy resources or are
cogenerators. Power providers are
required to purchase power at a rate
equal to the avoided cost of generating
the power themselves. (See Avoided Costs
and Qualifying Facility)
Holding Company Act (PUHCA) of 1935 A
law to protect consumers and investors.
It placed geographic restrictions on
mergers and limitations on
diversification into non-utility lines
of business and takeovers of electric
and gas utilities, and also established
regulated monopoly markets or service
territories for utilities.
Public Utility or
Services Commissions (PUC or PSC)
These are state government agencies
responsible for the regulation of public
utilities within a state or region. A
state legislature oversees the PUC by
reviewing changes to power generator
laws, rules and regulations and
approving the PUC's budget. The
commission usually has five
Commissioners appointed by the Governor
or legislature. PUCs typically regulate:
electric, natural gas, water, sewer,
telephone services, trucks, buses, and
taxicabs within the commission's
operating region. The PUC tries to
balance the interests of consumers,
environmentalists, utilities, and
stockholders. The PUC makes sure a
region's citizens are supplied with
adequate, safe power provider service at
(PWM) Wave Inverter A type of power
inverter that produce a high quality
(nearly sinusoidal) voltage, at minimum
Facility A type of power generating
facility that pumps water to a storage
reservoir during off-peak periods, and
uses the stored water (by allowing it to
fall through a hydro turbine) to
generate power during peak periods. The
pumping energy is typically supplied by
lower cost base power capacity, and the
peaking power capacity is of greater
value, even though there is a net loss
of power in the process.
device used to measure total incident
solar radiation (direct beam, diffuse,
and reflected radiation) per unit time
per unit area.
device that measures the intensity of
direct beam solar radiation.
transformation on a compound or material
into one or more substances by heat
alone (without oxidation). Often called
destructive distillation. Pyrolysis of
biomass is the thermal degradation of
the material in the absence of reacting
gases, and occurs prior to or
simultaneously with gasification
reactions in a gasifier. Pyrolysis
products consist of gases, liquids, and
char generally. The liquid fraction of
pyrolisized biomass consists of an
insoluble viscous tar, and pyroligneous
acids (acetic acid, methanol, acetone,
esters, aldehydes, and furfural). The
distribution of pyrolysis products
varies depending on the feedstock
composition, heating rate, temperature,
quadrillion Btu. (1,000,000,000,000,000
Quadrillion Btu One
quadrillion (1015= 10 to the 15th power)
British thermal units (Btu).
A category of electric power producer
established under the Public Utility
Regulatory Policy Act (PURPA) of 1978,
that includes small-power producers (SPP)
who use renewable sources of energy such
as biomass, geothermal,
hydroelectricity, solar (thermal and
photovoltaic), and wind, or cogenerators
who produce both heat and electricity
using any type of fuel. PURPA requires
utilities to purchase electricity from
these power producers at a rate approved
by a state utility regulatory agency
under Federal guidelines. PURPA also
requires power providers to sell
electricity to these producers. Some
states have developed their own programs
for SPPs and utilities.
Radiant Barrier A
thin, reflective foil sheet that
exhibits low radiant energy transmission
and under certain conditions can block
radiant heat transfer; installed in
attics to reduce heat flow through a
roof assembly into the living space.
Panels Ceiling panels that contain
electric resistance heating elements
embedded within them to provide radiant
heat to a room.
Radiant Energy Any
form of energy radiating from a source
in waves.Radiant Energy Energy that
transmits away from its source in all
Radiant Floor A
type of radiant heating system where the
building floor contains channels or
tubes through which hot fluids such as
air or water are circulated. The whole
floor is evenly heated. Thus, the room
heats from the bottom up. Radiant floor
heating eliminates the draft and dust
problems associated with forced air
System A heating system where heat is
supplied (radiated) into a room by means
of heated surfaces, such as electric
resistance elements, hot water (hydronic)
highspeed transmission of energy in the
form of particles or electromagnetic
waves. The transfer of heat through
matter or space by means of
The process of cooling by which a heat
absorbing media absorbs heat from one
source and radiates the heat away.
Radiator A room
heat delivery (or exchanger) component
of a hydronic (hot water or steam)
heating system; hot water or steam is
delivered to it by natural convection or
by a pump from a boiler.
Radiator Vent A
device that releases pressure within a
radiator when the pressure inside
exceeds the operating limits of the
An element whose atoms have unstable
nuclei that stabilizes itself by giving
Materials left over from making nuclear
energy. Radioactive waste can harm
people and the environment if it is not
property possessed by some elements,
such as uranium, of giving off alpha,
beta, or gamma rays.
Radon A naturally
occurring radioactive gas found in the
U.S. in nearly all types of soil, rock,
and water. It can migrate into most
buildings. Studies have linked high
concentrations of radon to lung cancer.
construction element used for ceiling
Rammed Earth A
construction material made by
compressing earth in a form; used
traditionally in many areas of the world
and widely throughout North Africa and
the Middle East.
Rankine Cycle The
thermodynamic cycle that is an ideal
standard for comparing performance of
heat-engines, steam power plants, steam
turbines, and heat pump systems that use
a condensable vapor as the working
fluid; efficiency is measured as work
done divided by sensible heat supplied.
Rate Schedule A
mechanism used by electric utilities to
determine prices for electricity;
typically defines rates according to
amounts of power demanded/consumed
during specific time periods.
Rated Life The
length of time that a product or
appliance is expected to meet a certain
level of performance under nominal
operating conditions; in a luminaire,
the period after which the lumen
depreciation and lamp failure is at 70%
of its initial value.
Rated Power The
power output of a device under specific
or nominal operating conditions.
Distribution A mathematical
representation of the frequency or ratio
that specific wind speeds occur within a
specified time interval.
Reactive Power The
electrical power that oscillates between
the magnetic field of an inductor and
the electrical field of a capacitor.
Reactive power is never converted to
non-electrical power. Calculated as the
square root of the difference between
the square of the kilovolt-amperes and
the square of the kilowatts. Expressed
as reactive volt-amperes.
Reactor Core Part
of a nuclear power station the
structure inside which fission occurs in
millions of atomic nuclei, producing
huge amounts of heat energy.
Real Price The unit
price of a good or service estimated
from some base year in order to provide
a consistent means of comparison.
component of a central receiver solar
thermal system where reflected solar
energy is absorbed and converted to
(Solar) A panel that contains a
battery of solar cells.
Air that is returned from a heated or
cooled space, reconditioned and/or
cleaned, and returned to the space.
A type of solar heating system that
circulate warm water from storage
through the collectors and exposed
piping whenever freezing conditions
occur; obviously a not very efficient
system when operating in this mode.
electrical device for converting
alternating current to direct current.
The chamber in a cooling device where
water is separated from the working
fluid (for example ammonia).
Recuperator A heat
exchanger in which heat is recovered
from the products of combustion.
Costs that are repetitive and occur when
an organization produces similar goods
or services on a continuing basis.
process of converting materials that are
no longer useful as designed or intended
into a new product.
Products Refined petroleum products
include but are not limited to gasoline,
kerosene, distillates (including No. 2
fuel oil), liquefied petroleum gas,
asphalt, lubricating oils, diesel fuels,
and residual fuels.
industrial plant that heats crude oil
(petroleum) so that is separates into
chemical components, which are then made
into more useful substances.
amount (percent) of light that is
reflected by a surface relative to the
amount that strikes it.
Materials with various qualities that
are applied to glass windows before
installation. These coatings reduce
radiant heat transfer through the window
and also reflects outside heat and a
portion of the incoming solar energy,
thus reducing heat gain. The most common
type has a sputtered coating on the
inside of a window unit. The other type
is a durable "hard-coat" glass with a
coating, baked into the glass surface.
Reflective Glass A
window glass that has been coated with a
reflective film and is useful in
controlling solar heat gain during the
(see also radiant barrier) An aluminum
foil fabricated insulator with backings
applied to provide a series of closed
air spaces with highly reflective
Films A material applied to window
panes that controls heat gain and loss,
reduces glare, minimizes fabric fading,
and provides privacy. These films are
retrofitted on existing windows.
Reflector Lamps A
type of incandescent lamp with an
interior coating of aluminum that
reflects light to the front of the bulb.
They are designed to spread light over
change in direction of a ray of light
when it passes through one media to
another with differing optical
compound (working fluid) used in air
conditioners, heat pumps, and
refrigerators to transfer heat into or
out of an interior space. This fluid
boils at a very low temperature enabling
it to evaporate and absorb heat.
process of the absorption of heat from
one location and its transfer to another
for rejection or recuperation. To make
or keep food cold or cool by using a
Capacity A measure of the effective
cooling capacity of a refrigerator,
expressed in Btu per hour or in tons,
where one (1) ton of capacity is equal
to the heat required to melt 2,000
pounds of ice in 24 hours or 12,000 Btu
The complete cycle of stages
(evaporation and condensation) of
refrigeration or of the refrigerant.
Refuse-Derived Fuel (RDF)
A solid fuel produced by shredding
municipal solid waste (MSW).
Noncombustible materials such as glass
and metals are generally removed prior
to making RDF. The residual material is
sold as-is or compressed into pellets,
bricks, or logs. RDF processing
facilities are typically located near a
source of MSW, while the RDF combustion
facility can be located elsewhere.
Existing RDF facilities process between
100 and 3,000 tons per day.
A type of cooling system that uses a
charging and discharging cycle with a
thermal or latent heat storage
The process of using heat that is
rejected in one part of a cycle for
another function or in another part of
Regional Plan Every
five years the Northwest Power Planning
Council releases a regional electric
power plan that is designed to guide
utilities and BPA toward the most
costeffective, environmentally sound
resources. BPA must observe the plan,
but it is primarily advisory to other
utilities in the region.
replacement of a non-functional or
ineffective lamp with a new, more
Relative Humidity A
measure of the percent of moisture
actually in the air compared with what
would be in it if it were fully
saturated at that temperature. When the
air is fully saturated, its relative
humidity is 100 percent.
Reliability This is
the concept of how long a device or
process can operate properly without
needing maintenance or replacement.
Energy derived from resources that are
regenerative or for all practical
purposes can not be depleted. Types of
renewable energy resources include
moving water (hydro, tidal and wave
power), thermal gradients in ocean
water, biomass, geothermal energy, solar
energy, and wind energy. Municipal solid
waste (MSW) is also considered to be a
renewable energy resource.
Sources Fuels that can be easily made
or "renewed." We can never use up
renewable fuels. Types of renewable
fuels are solar, wind, and hydropower
Energy resources used to generate
electricity and/or provide direct energy
services without relying on fossil or
depletable fuels. Examples include solar
hot water heating, solar electricity
generation, wind generation, geothermal
heating or electricity generation, and
(of the Economy) The part of the
economy having to do with the places
people stay or live. The residential
sector is made up of homes, apartments,
inherent characteristic of a material to
inhibit the transfer of energy. In
electrical conductors, electrical
resistance results in the generation of
heat. Electrical resistance is measured
in Ohms. The heat transfer resistance
properties of insulation products are
quantified as the R-value.
A type of heating system that provides
heat from the resistance of an
electrical current flowing through a
conductor.Resistive Voltage Drop The
voltage developed across a cell by the
current flow through the resistance of
electrical device that resists electric
The process of converting municipal
solid waste to energy and/or recovering
materials for recycling.
process of changing the structure of the
electric power industry from one of
guaranteed monopoly over service
territories, as established by the
Public Utility Holding Company Act of
1935, to one of open competition between
power suppliers for customers in any
Retail Wheeling A
term for the process of transmitting
electricity over transmission lines not
owned by the supplier of the electricity
to a retail customer of the supplier.
With retail wheeling, an electricity
consumer can secure their own supply of
electricity from a broker or directly
from the generating source. The power is
then wheeled at a fixed rate, or at a
regulated "non-discriminatory" rate set
by a utility commission.
process of modifying a building's
Return Air Air that
is returned to a heating or cooling
appliance from a heated or cooled space.
Return Duct The
central heating or cooling system
contains a fan that gets its air supply
through these ducts, which ideally
should be installed in every room of the
house. The air from a room will move
towards the lower pressure of the return
Thermosiphoning When heat seeks to
flow from a warm area (e.g., heated
space) to a cooler area, such as a solar
air collector at night without a reverse
Reversing Valve A
component of a heat pump that reverses
the refrigerant's direction of flow,
allowing the heat pump to switch from
cooling to heating or heating to
Cells A type of solar photovoltaic
device made in a continuous process of
pulling material from a molten bath of
photovoltaic material, such as silicon,
to form a thin sheet of material.
Board An insulation product made of a
fibrous material or plastic foams,
pressed or extruded into board-like
forms. It provides thermal and
acoustical insulation strength with low
weight, and coverage with few heat loss
Rock Bin A
container that holds rock used as the
thermal mass to store solar energy in a
solar heating system.
Rock Wool A type of
insulation made from virgin basalt, an
igneous rock, and spun into loose fill
or a batt. It is fire resistant and
helps with soundproofing.
Roof A building
element that provides protection against
the sun, wind, and precipitation.
Roof Pond A solar
energy collection device consisting of
containers of water located on a roof
that absorb solar energy during the day
so that the heat can be used at night or
that cools a building by evaporation at
Roof Ventilator A
stationary or rotating vent used to
ventilate attics or cathedral ceilings;
usually made of galvanized steel, or
Rotor An electric
generator consists of an armature and a
field structure. The armature carries
the wire loop, coil, or other windings
in which the voltage is induced, whereas
the field structure produces the
magnetic field. In small generators, the
armature is usually the rotating
component (rotor) surrounded by the
stationary field structure (stator). In
large generators in commercial electric
power plants the situation is reversed.
In a wind energy conversion device, the
blades and rotating components.
Hydropower A type of hydroelectric
facility that uses the river flow with
very little alteration and little or no
impoundment of the water.
Administration (REA) An agency of the
U.S. Dept. of Agriculture that makes
loans to states and territories in the
U.S. for rural electrification and the
furnishing of electric energy to persons
in rural areas who do not receive
central station service. It also
furnishes and improves electric and
telephone service in rural areas,
assists electric borrowers to implement
energy conservation programs and on-grid
and off-grid renewable energy systems,
and studies the condition and progress
of rural electrification.
RValue A measure
of a material's resistance to heat flow
in units of Fahrenheit degrees x hours x
square feet per Btu. The higher the
Rvalue of a material, the greater its
insulating capability. The R-Value is
the reciprocal of the conductivity of a
Sacrificial Anode A
metal rod placed in a water heater tank
to protect the tank from corrosion.
Anodes of aluminum, magnesium, or zinc
are the more frequently metals. The
anode creates a galvanic cell in which
magnesium or zinc will be corroded more
quickly than the metal of the tank
giving the tank a negative charge and
An electronic (automatic or manual)
switch that disconnects one circuit from
another circuit. These are used to
isolate power generation or storage
equipment from conditions such as
voltage spikes or surges, thus avoiding
potential damage to equipment.
Salt Gradient Solar
Ponds Consist of three main layers.
The top layer is near ambient and has
low salt content. The bottom layer is
hot, typically 160 F to 212 F (71 C to
100 C), and is very salty. The important
gradient zone separates these zones. The
gradient zone acts as a transparent
insulator, permitting the sunlight to be
trapped in the hot bottom layer (from
which useful heat is withdrawn). This is
because the salt gradient, which
increases the brine density with depth,
counteracts the buoyancy effect of the
warmer water below (which would
otherwise rise to the surface and lose
its heat to the air). An organic Rankine
cycle engine is used to convert the
thermal energy to electricity.
cutting of a grid pattern of grooves in
a semiconductor material, generally for
the purpose of making interconnections.
Heating System A heating system that
uses only outside air for combustion and
vents combustion gases directly to the
outdoors. These systems are less likely
to backdraft and to negatively affect
indoor air quality.
Efficiency Ratio (SEER) A measure of
seasonal or annual efficiency of a
central air conditioner or air
conditioning heat pump. It takes into
account the variations in temperature
that can occur within a season and is
the average number of Btu of cooling
delivered for every watt-hour of
electricity used by the heat pump over a
Factor (SPF) Ratio of useful energy
output of a device to the energy input,
averaged over an entire heating season.
Seasoned Wood Wood,
used for fuel, that has been air dried
so that it contains 15 to 20 percent
moisture content (wet basis).
Second Law Efficiency
The ratio of the minimum amount of
work or energy required to perform a
task to the amount actually used.
Second Law of
Thermodynamics This law states that no
device can completely and continuously
transform all of the energy supplied to
it into useful energy.
Seebeck Effect The
generation of an electric current, when
two conductors of different metals are
joined at their ends to form a circuit,
with the two junctions kept at different
Selectable Load Any
device, such as lights, televisions, and
power tools, which is plugged into your
central power source and used only
A solar absorber surface that has high
absorbence at wavelengths corresponding
to that of the solar spectrum and low
emittance in the infrared range.
Coating A material with high
absorbence and low emittance properties
applied to or on solar absorber
material that has a limited capacity for
conducting an electric current. Certain
semiconductors, including silicon,
gallium arsenide, copper indium
diselenide, and cadmium telluride, are
uniquely suited to the photovoltaic
conversion process. Semiconductors are
crystalline solids, such as silicon,
that have an electrical conductivity
between that of a conductor and an
Senate Committee on
Energy and Natural Resources This
committee has jurisdiction on: coal
production, distribution and
utilization; energy policy; energy
research, conservation, and development;
hydroelectric power; irrigation; mineral
conservation; nonmilitary development of
nuclear energy; solar energy systems;
and over territorial possessions,
including trusteeships of the United
on Energy Research, Development,
Production and Regulation This
committee has jurisdiction on the
oversight and legislative
responsibilities for: coal, nuclear, and
non-nuclear energy commercialization
projects; DOE National Laboratories;
global climate change; new technologies
research and development;
commercialization of new technologies
including, solar energy systems; Federal
energy conservation programs; energy
information; and power provider policy.
Effect The difference between the
total cooling effect and the
Sensible Cooling Load
The interior heat gain due to heat
conduction, convection, and radiation
from the exterior into the interior, and
from occupants and appliances.
Sensible Heat The
heat absorbed or released when a
substance undergoes a change in
Sensible Heat Storage
A heat storage system that uses a heat
storage medium, and where the additional
or removal of heat results in a change
configuration of an electrical circuit
in which the positive lead is connected
to the negative lead of another energy
producing, conducting, or consuming
device. The voltages of each device are
additive, whereas the current is not.
Series Connection A
way of joining photovoltaic cells by
connecting positive leads to negative
leads; such a configuration increases
Parasitic resistance to current flow in
a cell due to mechanisms such as
resistance from the bulk of the
semiconductor material, metallic
contacts, and interconnections.
Territory in which a utility system is
required to or has the right to supply
natural gas service to ultimate
A thermostat that can be set to
automatically lower temperatures in an
unoccupied house and raise them again
before the occupant returns.
A measure of window glazing performance
that is the ratio of the total solar
heat gain through a specific window to
the total solar heat gain through a
single sheet of double-strength glass
under the same set of conditions;
expressed as a number between 0 and 1.
Shaft mine A mine
that reaches the coal bed by means of a
construction element used to cover the
exterior of wall framing and roof
Short Circuit An
electric current taking a shorter or
different path than intended.
Short Circuit Current
The current flowing freely through an
external circuit that has no load or
resistance; the maximum current
Short ton A unit of
weight equal to 2,000 pounds, often used
to measure coal.
Shunt Load An
electrical load used to safely use
excess generated power when not needed
for its primary uses. A shunt load in a
residential photovoltaic system might be
domestic water heating, such that when
power is not needed for typical building
loads, such as operating lights or
running HVAC system fans and pumps, it
still provides value and is used in a
constructive, safe manner.
Shutter An interior
or exterior movable panel that operates
on hinges or slides into place, used to
protect windows or provide privacy.
construction element applied to the
outermost surface of an exterior wall.
Sigma Heat The sum
of sensible heat and latent heat in a
substance above a base temperature,
typically 32 degrees Fahrenheit.
Silicon A chemical
element, of atomic number 14, that is
semi-metallic, and an excellent
semiconductor material used in solar
photovoltaic devices; commonly found in
Simple CS (Caulk and
Seal) A technique for insulating and
sealing exterior walls that reduces
vapor diffusion through air leakage
points by installing pre-cut blocks of
rigid foam insulation over floor joists,
sheet subfloor, and top plates before
drywall is installed.
Sine Wave The type
of alternative current generated by
alternating current generators, rotary
inverters, and solid-state inverters.
Single Glaze or Pane
One layer of glass in a window frame.
It has very little insulating value
(R-1) and provides only a thin barrier
to the outside and can account for
considerable heat loss and gain.
Material In reference to solar
photovoltaic devices, a material that is
composed of a single crystal or a few
A year 'round heating and air
conditioning system that has all the
components completely encased in one
unit outside the home. Proper matching
of components can mean more
energy-efficient operation compared to
components purchased separately.
generator with a single armature coil,
which may have many turns and the
alternating current output consists of a
succession of cycles.
Sizing The process
of designing a solar system to meet a
specified load given the solar resource
and the nominal or rated energy output
of the solar energy collection or
Skylight A window
located on the roof of a structure to
provide interior building spaces with
natural daylight, warmth, and
Slab A concrete pad
that sits on gravel or crushed rock,
well-compacted soil either level with
the ground or above the ground.
Slab on Grade A
slab floor that sits directly on top of
the surrounding ground.
SlinkyTM Ground Loop
In this type of closed-loop,
horizontal geothermal heat pump
installation, the fluid-filled plastic
heat exchanger pipes are coiled like a
Slinky to allow more pipe in a shorter
trench. This type of installation cuts
down on installation costs and makes
horizontal installation possible in
areas it would not be with conventional
horizontal applications. Also see
closed-loop geothermal heat pump
Smart Window A term
used to describe a technologically
advanced window system that contains
glazing that can change or switch its
optical qualities when a low voltage
electrical signal is applied to it, or
in response to changes in heat or light.
Sodium Lights A
type of high intensity discharge light
that has the most lumens per watt of any
Soffit A panel
which covers the underside of an roof
overhang, cantilever, or mansard.
Solar Access or
Rights The legal issues related to
protecting or ensuring access to
sunlight to operate a solar energy
system, or use solar energy for heating
Solar Air Heater A
type of solar thermal system where air
is heated in a collector and either
transferred directly to the interior
space or to a storage medium, such as a
Solar Altitude Angle
The angle between a line from a point
on the earth's surface to the center of
the solar disc, and a line extending
horizontally from the point.
Solar Array A group
of solar collectors or solar modules
Solar Azimuth The
angle between the sun's apparent
position in the sky and true south, as
measured on a horizontal plane.
Solar Cell A solar
photovoltaic device with a specified
area. An electric cell which changes
radiant energy from the sun into
electrical energy by the photovoltaic
Solar Collector A
device used to collect, absorb, and
transfer solar energy to a working
fluid. Flat plate collectors are the
most common type of collectors used for
solar water or pool heating systems. In
the case of a photovoltaics system, the
solar collector could be crystalline
silicon panels or thin-film roof
shingles, for example.
Solar Constant The
average amount of solar radiation that
reaches the earth's upper atmosphere on
a surface perpendicular to the sun's
rays; equal to 1353 Watts per square
meter or 492 Btu per square foot.
Solar Cooling The
use of solar thermal energy or solar
electricity to power a cooling
appliance. There are five basic types of
solar cooling technologies: absorption
cooling, which can use solar thermal
energy to vaporize the refrigerant;
desiccant cooling, which can use solar
thermal energy to regenerate (dry) the
desiccant; vapor compression cooling,
which can use solar thermal energy to
operate a Rankine-cycle heat engine; and
evaporative coolers ("swamp" coolers),
and heat-pumps and air conditioners that
can by powered by solar photovoltaic
The apparent angle of the sun north or
south of the earth's equatorial plane.
The earth's rotation on its axis causes
a daily change in the declination.
Solar Dish A device
that receives radiation collected by
motorized collectors which track the
sun. The collectors focus the radiation
the energy at a focal point of the dish.
The process of distilling (purifying)
water using solar energy. Water can be
placed in an air tight solar collector
with a sloped glazing material, and as
it heats and evaporates, distilled water
condenses on the collector glazing, and
runs down where it can be collected in a
Electromagnetic energy transmitted from
the sun (solar radiation). The amount
that reaches the earth is equal to one
billionth of total solar energy
generated, or the equivalent of about
420 trillion kilowatt-hours. The radiant
energy of the sun, which can be
converted into other forms of energy,
such as heat or electricity.
Collector See solar collector.
Industries Association (SEIA) A
national trade association of solar
energy equipment manufacturers,
retailers, suppliers, installers, and
Solar Energy Research
Institute (SERI) A federally funded
institute, created by the Solar Energy
Research, Development and Demonstration
Act of 1974, that conducted research and
development of solar energy
technologies. Became the National
Renewable Energy Laboratory (NREL) in
Solar Film A window
glazing coating, usually tinted bronze
or gray, used to reduce building cooling
loads, glare, and fabric fading.
Solar Fraction The
percentage of a building's seasonal
energy requirements that can be met by a
solar energy device(s) or system(s).
Solar Furnace A
device that achieves very high
temperatures by the use of reflectors to
focus and concentrate sunlight onto a
Solar Gain The
amount of energy that a building absorbs
due to solar energy striking its
exterior and conducting to the interior
or passing through windows and being
absorbed by materials in the building.
The amount of solar radiation, both
direct and diffuse, received at any
Solar Mass A term
used for materials used to absorb and
store solar energy.
Solar Module (Panel)
A solar photovoltaic device that
produces a specified power output under
defined test conditions, usually
composed of groups of solar cells
connected in series, in parallel, or in
Solar Noon The time
of the day, at a specific location, when
the sun reaches its highest, apparent
point in the sky; equal to true or due,
Solar One A solar
thermal electric central receiver power
plant ("power tower") located in
Barstow, California, and completed in
1981. The Solar One had a design
capacity of 10,000 peak kilowatts, and
was composed of a receiver located on
the top of a tower surrounded by a field
of reflectors. The concentrated sunlight
created steam to drive a steam turbine
and electric generator located on the
Solar Panel See
Solar Pond A body
of water that contains brackish (highly
saline) water that forms layers of
differing salinity (stratifies) that
absorb and trap solar energy. Solar
ponds can be used to provide heat for
industrial or agricultural processes,
building heating and cooling, and to
Solar Power Satellite
A solar power station investigated by
NASA that entailed a satellite in
geosynchronous orbit that would consist
of a very large array of solar
photovoltaic modules that would convert
solar generated electricity to
microwaves and beam them to a fixed
point on the earth.
Solar Power Tower
The conceptual method of producing
electrical energy from solar rays. It
involved the focusing of a large number
of solar rays on a single source
(boiler), usually located on an elevated
tower, to produce high temperatures. A
fluid located in or passed through the
source changes into steam and used in a
turbine generator to produce electrical
Solar Radiation A
general term for the visible and near
visible (ultraviolet and near-infrared)
electromagnetic radiation that is
emitted by the sun. It has a spectral,
or wavelength, distribution that
corresponds to different energy levels;
short wavelength radiation has a higher
energy than long-wavelength radiation.
Solar Simulator An
apparatus that replicates the solar
spectrum, and used for testing solar
energy conversion devices.
Solar Space Heater
A solar energy system designed to
provide heat to individual rooms in a
Solar spectrum The
total distribution of electromagnetic
radiation emanating from the sun. The
different regions of the solar spectrum
are described by their wavelength range.
The visible region extends from about
390 to 780 nanometers (a nanometer is
one billionth of one meter). About 99
percent of solar radiation is contained
in a wavelength region from 300 nm
(ultraviolet) to 3,000 nm
(near-infrared). The combined radiation
in the wavelength region from 280 nm to
4,000 nm is called the broadband, or
total, solar radiation.
Electric Systems Solar energy
conversion technologies that convert
solar energy to electricity, by heating
a working fluid to power a turbine that
drives a generator. Examples of these
systems include central receiver
systems, parabolic dish, and solar
trough. The systems use concentrating
collectors to focus the sun's radiant
energy onto or into receivers to produce
Parabolic Dishes A solar thermal
technology that uses a modular mirror
system that approximates a parabola and
incorporates two-axis tracking to focus
the sunlight onto receivers located at
the focal point of each dish. The mirror
system typically is made from a number
of mirror facets, either glass or
polymer mirror, or can consist of a
single stretched membrane using a
polymer mirror. The concentrated
sunlight may be used directly by a
Stirling, Rankine, or Brayton cycle heat
engine at the focal point of the
receiver or to heat a working fluid that
is piped to a central engine. The
primary applications include remote
electrification, water pumping, and
Solar Thermal Systems
Solar energy systems that collect or
absorb solar energy for useful purposes.
Can be used to generate high temperature
heat (for electricity production and/or
process heat), medium temperature heat
(for process and space/water heating and
electricity generation), and low
temperature heat (for water and space
heating and cooling).
Solar Time The
period marked by successive crossing of
the earth's meridian by the sun; the
hour angle of the sun at a point of
observance (apparent time) is corrected
to true (solar) time by taking into
account the variation in the earth's
orbit and rate of rotation. Solar time
and local standard time are usually
different for any specific location.
The amount of solar energy that passes
through a glazing material, expressed as
Solar Trough Systems
(see also Parabolic Trough, above) A
type of solar thermal system where
sunlight is concentrated by a curved
reflector onto a pipe containing a
working fluid that can be used for
process heat or to produce electricity.
The world's largest solar thermal
electric power plants use solar trough
technology. They are located in
California, and have a combined
electricity generating capacity of
Solar Two Solar Two
is a retrofit of the Solar One project
(see above). It is demonstrating the
technical feasibility and power
potential of a solar power tower using
advanced molten-salt technology to store
energy. Solar Two retains several of the
main components of Solar One, including
the receiver tower, turbine, generator,
and the 1,818 heliostats.
Solarium A glazed
structure, such as greenhouse or
electromechanical device composed of a
coil of wire wound around a cylinder
containing a bar or plunger, that when a
current is applied to the coil, the
electromotive force causes the plunger
to move; a series of coils or wires used
to produce a magnetic field.
Solenoid Valve An
automatic valve that is opened or closed
by an electromagnet.
Solid fuel Coal and
Solid Fuels Any
fuel that is in solid form, such as
wood, peat, lignite, coal, and
manufactured fuels such as pulverized
coal, coke, charcoal, briquettes,
reference to a wind energy conversion
device, the ratio of rotor blade surface
area to the frontal, swept area that the
rotor passes through.
Solstice The two
times of the year when the sun is
apparently farthest north and south of
the earth's equator; usually occurring
on or around June 21 (summer solstice in
northern hemisphere, winter solstice for
southern hemisphere) and December 21
(winter solstice in northern hemisphere,
summer solstice for the southern
SOV single occupant
Space Heater A
movable or fixed heater used to heat
Space Heating The
use of energy to generate heat for
warmth in housing units using
spaceheating equipment. The equipment
could be the main spaceheating
equipment or secondary spaceheating
Strips of material used to separate
multiple panes of glass within the
Specific Heat The
amount of heat required to raise a unit
mass of a substance through one degree,
expressed as a ratio of the amount of
heat required to raise an equal mass of
water through the same range.
Capacity The quantity of heat required
to change the temperature of one unit
weight of a material by one degree.
The weight of water vapor, per unit
weight of dry air.
Specific Volume The
volume of a unit weight of a substance
at a specific temperature and pressure.
Distribution A curve illustrating the
variation or spectral irradiance with
The monochromatic irradiance of a
surface per unit bandwidth at a
particular wavelength, usually expressed
in Watts per square meter-nanometer
The ratio of energy reflected from a
surface in a given waveband to the
energy incident in that waveband.
Coatings A type of window glazing
films used to block the infrared (heat)
portion of the solar spectrum but admit
a higher portion of visible light.
Spectrum see Solar
Electromagnetic Radiation The name
that scientists give to a bunch of types
of radiation when they want to talk
about them as a group. The types of
radiation include the full range of
frequencies, from radio waves to gamma
waves, which characterize light.
Irradiated fuel that is permanently
discharged from a nuclear reactor.
Except for possible reprocessing, this
fuel must eventually be removed from its
temporary storage location at the
reactor site and placed in a permanent
repository. Spent fuel is typically
measured either in metric tons of heavy
metal (i.e., only the heavy metal
content of the spent fuel is considered)
or in metric tons of initial heavy metal
(essentially, the initial mass of the
fuel before irradiation). The difference
between these two quantities is the
weight of the fission products.
Spillway A passage
for surplus water to flow over or around
Electric power provider capacity on line
and running at low power in excess of
Photovoltaic Cell A photovoltaic
device where incident sunlight is split
into different spectral regions, with an
optical apparatus, that are directed to
individual photovoltaic cells that are
optimized for converting that spectrum
Split System Air
Conditioner An air conditioning system
that comes in two to five pieces: one
piece contains the compressor,
condenser, and a fan; the others have an
evaporator and a fan. The condenser,
installed outside the house, connects to
several evaporators, one in each room to
be cooled, mounted inside the house.
Each evaporator is individually
controlled, allowing different rooms or
zones to be cooled to varying degrees.
Spray Pyrolysis A
deposition process whereby heat is used
to break molecules into elemental
sources that are then spray deposited on
Spreader Stocker A
type of furnace in which fuel is spread,
automatically or mechanically, across
the furnace grate.
process used to apply photovoltaic
semi-conductor material to a substrate
by a physical vapor deposition process
where high-energy ions are used to
bombard elemental sources of
semiconductor material, which eject
vapors of atoms that are then deposited
in thin layers on a substrate.
Square Wave Inverter
A type of inverter that produces
square wave output.; consists of a DC
source, four switches, and the load. The
switches are power semiconductors that
can carry a large current and withstand
a high voltage rating. The switches are
turned on and off at a correct sequence,
at a certain frequency. The square wave
inverter is the simplest and the least
expensive to purchase, but it produces
the lowest quality of power.
Squirrel Cage Motors
This is another name for an induction
motor. The motors consist of a rotor
inside a stator. The rotor has
laminated, thin flat steel discs,
stacked with channels along the length.
If the casting composed of bars and
attached end rings were viewed without
the laminations the casting would appear
similar to a squirrel cage.
Stack A smokestack
or flue for exhausting the products of
combustion from a combustion appliance.
Stack (Heat) Loss
Sensible and latent heat contained in
combustion gases and vapor emitted to
effect The tendency of the sunlight to
electricity conversion efficiency of
amorphous silicon photovoltaic devices
to degrade (drop) upon initial exposure
Temperature A condition that can occur
in a solar collector if the working
fluid does not circulate when sun is
shining on the collector.
Stall In reference
to a wind turbine, a condition when the
rotor stops turning.
A power source/generator that operates
independently of or is not connected to
an electric transmission and
distribution network; used to meet a
load(s) physically close to the
An inverter that operates independent
of or is not connected to an electric
transmission and distribution network.
An system that operates independent of
or is not connected to an electric
transmission and distribution network.
Standard Air Air
with a weight of 0.075 pounds per cubic
foot with an equivalent density of dry
air at a temperature of 86 degrees
Fahrenheit and standard barometric
pressure of 29.92 inches of mercury.
In refrigeration, an evaporating
temperature of 5 degrees Fahrenheit (F),
a condensing temperature of 86 degrees
F., liquid temperature before expansion
of 77 degrees F., and suction
temperature of 12 degrees F.
Standard Cubic Foot
A column of gas at standard conditions
of temperature and pressure (32 degrees
Fahrenheit and one atmosphere).
Classification (SIC) Code Standardized
codes used to classify businesses by
type of activity they engage in.
Stand-by Heat Loses
A term used to describe heat energy lost
from a water heater tank.
Stand-By Power For
the consumer, this is the electricity
that is used by your TVs, stereos, and
other electronic devices that use remote
controls. When you press "off" to turn
off your device, minimal power (dormant
mode) is still being used to maintain
the internal electronics in a ready,
quick-response mode. This way, your
device can be turned on with your remote
control and be immediately ready to
Power, often above an appliance's rated
wattage, required to bring any appliance
with a motor up to operating speed.
Starting Torque The
torque at the bottom of a speed (rpm)
versus torque curve. The torque
developed by the motor is a percentage
of the full-load or rated torque. At
this torque the speed, the rotational
speed of the motor as a percentage of
synchronous speed is zero. This torque
is what is available to initially get
the load moving and begin its
Static Pressure The
force per unit area acting on the
surface of a solid boundary parallel to
Steam Water in
vapor form; used as the working fluid in
steam turbines and heating systems.
Steam Boiler A type
of furnace in which fuel is burned and
the heat is used to produce steam.
Steam Generator A
generator in which the prime movers
(turbines) are powered by steam.
Steam Turbine A
device that converts high-pressure
steam, produced in a boiler, into
mechanical energy that can then be used
to produce electricity by forcing blades
in a cylinder to rotate and turn a
Stirling Engine A
heat engine of the reciprocating
(piston) where the working gas and a
heat source are independent. The working
gas is compressed in one region of the
engine and transferred to another region
where it is expanded. The expanded gas
is then returned to the first region for
recompression. The working gas thus
moves back and forth in a closed cycle.
The ratio of chemical substances
necessary for a reaction to occur
Chemical reactions, typically associated
with combustion processes; the balancing
of chemical reactions by providing the
exact proportions of reactant compounds
to ensure a complete reaction; all the
reactants are used up to produce a
single set of products.
The amount of energy an energy storage
device or system can store.
A hydropower facility that stores water
in a reservoir during high-inflow
periods to augment water during
low-inflow periods. Storage projects
allow the flow releases and power
production to be more flexible and
dependable. Many hydropower project
operations use a combination of
Storage Tank The
tank of a water heater.
Storage Water Heater
A water heater that releases hot water
from the top of the tank when a hot
water tap is opened. To replace that hot
water, cold water enters the bottom of
the tank to ensure a full tank.
Storm Door An
exterior door that protects the primary
Glass, plastic panels, or plastic sheets
that reduce air infiltration and some
heat loss when attached to either the
interior or exterior of existing
(Costs and Benefits) An investment in
a power plant or demand side management
measures or programs, that become
uneconomical due to increased
competition in the electric power
market. For example, an electric power
plant may produce power that is more
costly than what the market rate for
electricity is, and the power plant
owner may have to close the plant, even
though the capital and financing costs
of building the plant have not been
recovered through prior sales of
electricity from the plant. This is
considered a Stranded Cost. Stranded
Benefits are those power provider
investments in measures or programs
considered to benefit consumers by
reducing energy consumption and/or
providing environmental benefits that
have to be curtailed due to increased
competition and lower profit margins.
Stud A popular term
used for a length of wood or steel used
in or for wall framing.
electrical installation containing power
conversion (and sometimes generation)
equipment, such as transformers,
compensators, and circuit breakers.
physical material upon which a
photovoltaic cell is applied.
Sun Path Diagram A
circular projection of the sky vault
onto a flat diagram used to determine
solar positions and shading effects of
landscape features on a solar energy
Sun Tempered Building
A building that is elongated in the
east-west direction, with the majority
of the windows on the south side. The
area of the windows is generally limited
to about 7% of the total floor area. A
sun-tempered design has no added thermal
mass beyond what is already in the
framing, wall board, and so on.
Insulation levels are generally high.
Sunspace A room
that faces south (in the northern
hemisphere), or a small structure
attached to the south side of a house.
Houses A type of house that has
massive amounts of insulation, airtight
construction, and controlled ventilation
without sacrificing comfort, health, or
Super Window A
popular term for highly insulating
window with a heat loss so low it
performs better than an insulated wall
in winter, since the sunlight that it
admits is greater than its heat loss
over a 24 hour period.
Magnetic Energy Storage (SMES) SMES
technology uses the superconducting
characteristics of low-temperature
materials to produce intense magnetic
fields to store energy. SMES has been
proposed as a storage option to support
large-scale use of photovoltaics and
wind as a means to smooth out
fluctuations in power generation.
The abrupt and large increase in
electrical conductivity exhibited by
some metals as the temperature
approaches absolute zero.
A heat source, such as a space heater,
used to provide more heat than that
provided by a primary heating source.
Supply Duct The
duct(s) of a forced air heating/cooling
system through which heated or cooled
air is supplied to rooms by the action
of the fan of the central heating or
Technologies that pertain to the
generation of electricity.
resources Fuels and other methods of
Surface Mine A
coalproducing mine that is usually
within a few hundred feet of the
surface. Earth above or around the coal
(overburden) is removed to expose the
coal bed, which is then mined with
surface excavation equipment, such as
draglines, power shovels, bulldozers,
loaders, and augers. It may also be
known as an area, contour, openpit,
strip, or auger mine.
Surface Water Loop
In this type of closed-loop geothermal
heat pump installation, the fluid-filled
plastic heat exchanger pipes are coiled
into circles and submerged at least
eight feet below the surface of a body
of surface water, such as a pond or
lake. The coils should only be placed in
a water source that meets minimum
volume, depth, and quality criteria.
Also see closed-loop geothermal heat
Swamp Cooler A
popular term used for an evaporative
Swept Area In
reference to a wind energy conversion
device, the area through which the rotor
blades spin, as seen when directly
facing the center of the rotor blades.
An electrical generator that runs at a
constant speed and draws its excitation
from a power source external or
independent of the load or transmission
network it is supplying.
An electrical inverter that inverts
direct current electricity to
alternating current electricity, and
that uses another alternating current
source, such as an electric power
transmission and distribution network
(grid), for voltage and frequency
reference to provide power in phase and
at the same frequency as the external
Synchronous Motor A
type of motor designed to operate
precisely at the synchronous speed with
no slip in the full-load speeds (rpm).
System Mix The
proportion of electricity distributed by
a power provider that is generated from
available sources such as coal, natural
gas, petroleum, nuclear, hydropower,
wind, or geothermal.
Tank Farm An
installation used by trunk and gathering
pipeline companies, crude oil producers,
and terminal operators (except
refineries) to store crude oil.
Tanker and Barge
Vessels that transport crude oil or
Tankless Water Heater
A water heater that heats water before
it is directly distributed for end use
as required; a demand water heater.
Task Lighting Any
light source designed specifically to
direct light a task or work performed by
a person or machine.
Transmitting information (could be
voice, data, or video signals) by wire,
optical cable, radio waves, or similar
telecommunication technology such as
telephones, personal computers, and fax
machines in ways that permit employees
to work at locations away from the main
office and, by doing so, avoid
Coefficient (of a solar photovoltaic
cell) The amount that the voltage,
current, and/or power output of a solar
cell changes due to a change in the cell
Index An index that combines sensible
temperature and air humidity to arrive
at a number that closely responds to the
effective temperature; used to relate
temperature and humidity to levels of
Individual rooms or zones in a building
where temperature is controlled
separately from other rooms or zones.
Relief Valve A component of a water
heating system that opens at a
designated temperature or pressure to
prevent a possible tank, radiator, or
delivery pipe rupture.
Tempering Valve A
valve used to mix heated water with cold
in a heating system to provide a desired
water temperature for end use.
Authority (TVA) A federal agency
established in 1933 to develop the
Tennessee river valley region of the
southeastern U.S., and which is now
nation's largest power producer.
Termite Shield A
construction element that inhibits
termites from entering building
foundations and walls.
Tesla Coil A device
for producing a highfrequency,
highvoltage electric current.
Therm 100,000 Btus;
the amount of heat energy in
approximately 100 cubic feet of natural
gas. One therm is equivalent to 29.3
Therm A unit of
heat containing 100,000 British thermal
Thermal Balance Point
The point or outdoor temperature where
the heating capacity of a heat pump
matches the heating requirements of a
The ability of a material to absorb and
store heat for use later.
A measure of the efficiency of
converting a fuel to energy and useful
work; useful work and energy output
divided by higher heating value of input
fuel times 100 (for percent).
Thermal Energy The
energy developed through the use of heat
energy.The total potential and kinetic
energy associated with the random
motions of the molecules of a material.
Storage The storage of heat energy
during power provider off-peak times at
night, for use during the next day
without incurring daytime peak electric
Houses An architectural design (also
known as the double envelope house),
sometimes called a
"house-within-a-house," that employs a
double envelope with a continuous
airspace of at least 6 to 12 inches on
the north wall, south wall, roof, and
floor, achieved by building inner and
outer walls, a crawl space or
sub-basement below the floor, and a
shallow attic space below the weather
roof. The east and west walls are
single, conventional walls. A buffer
zone of solar-heated, circulating air
warms the inner envelope of the house.
The south-facing airspace may double as
a sunspace or greenhouse.
Materials that store heat.
(R-Value) This designates the
resistance of a material to heat
conduction. The greater the R-value the
larger the number.
Thermal Storage Walls
(Masonry or Water) A thermal storage
wall is a south-facing wall that is
glazed on the outside. Solar heat
strikes the glazing and is absorbed into
the wall, which conducts the heat into
the room over time. The walls are at
least 8 in thick. Generally, the thicker
the wall, the less the indoor
device consisting of two dissimilar
conductors with their ends connected
together. When the two junctions are at
different temperatures, a small voltage
An idealized process in which a working
fluid (water, air, ammonia, etc)
successively changes its state (from a
liquid to a gas and back to a liquid)
for the purpose of producing useful work
or energy, or transferring energy.
study of the transformation of energy
from one form to another, and its
practical application. (see Law(s) of
Conversion The conversion of heat into
electricity by the use of thermocouples.
building energy auditing technique for
locating areas of low insulation in a
building envelope by means of a
Cell A device where sunlight
concentrated onto a absorber heats it to
a high temperature, and the thermal
radiation emitted by the absorber is
used as the energy source for a
photovoltaic cell that is designed to
maximize conversion efficiency at the
wavelength of the thermal radiation.
Thermopile A large
number of thermocouples connected in
natural, convective movement of air or
water due to differences in temperature.
In solar passive design a thermosyphon
collector can be constructed and
attached to a house to deliver heat to
the home by the continuous pattern of
the convective loop (or thermosyphon).
This passive solar hot water system
consists relies on warm water rising, a
phenomenon known as natural convection,
to circulate water through the
collectors and to the tank. In this type
of installation, the tank must be above
the collector. As water in the collector
heats, it becomes lighter and rises
naturally into the tank above.
Meanwhile, cooler water in the tank
flows down pipes to the bottom of the
collector, causing circulation
throughout the system. The storage tank
is attached to the top of the collector
so that thermosiphoning can occur.
Thermostat A device
used to control temperatures; used to
control the operation of heating and
cooling devices by turning the device on
or off when a specified temperature is
Thin-Film A layer
of semiconductor material, such as
copper indium diselenide or gallium
arsenide, a few microns or less in
thickness, used to make solar
Alternating current in which three
separate pulses are present, identical
in frequency and voltage, but separated
120 degrees in phase.
Tidal Power The
power available from the rise and fall
of ocean tides. A tidal power plant
works on the principal of a dam or
barrage that captures water in a basin
at the peak of a tidal flow, then
directs the water through a
hydroelectric turbine as the tide ebbs.
Tilt Angle (of a
Solar Collector or Module) The angle
at which a solar collector or module is
set to face the sun relative to a
horizontal position. The tilt angle can
be set or adjusted to maximize seasonal
or annual energy collection.
Rates The pricing of electricity based
on the estimated cost of electricity
during a particular time block.
Time-of-use rates are usually divided
into three or four time blocks per
twenty-four hour period (on-peak,
mid-peak, off-peak and sometimes super
off-peak) and by seasons of the year
(summer and winter). Real-time pricing
differs from TOU rates in that it is
based on actual (as opposed to
forecasted) prices which may fluctuate
many times a day and are
weather-sensitive, rather than varying
with a fixed schedule.
Timer A device that
can be set to automatically turn
appliances (lights) off and on at set
Timer (Water Heater)
This device can automatically turn the
heater off at night and on in the
Tip Speed Ratio In
reference to a wind energy conversion
device's blades, the difference between
the rotational speed of the tip of the
blade and the actual velocity of the
Ton (of Air
Conditioning) A unit of air cooling
capacity; 12,000 Btu per hour.
means to increase the thermal efficiency
of a steam electric generating system by
increasing temperatures and interposing
a device, such as a gas turbine, between
the heat source and the conventional
steam-turbine generator to convert some
of the additional heat energy into
Torque (Motor) The
turning or twisting force generated by
an electrical motor in order for it to
Distortion The measure of closeness in
shape between a waveform and it's
Total Heat The sum
of the sensible and latent heat in a
substance or fluid above a base point,
usually 32 degrees Fahrenheit.
Radiation The total radiation incident
on a specific surface area over a time
Reflection The trapping of light by
refraction and reflection at critical
angles inside a semiconductor device so
that it cannot escape the device and
must be eventually absorbed by the
Tracking Solar Array
A solar energy array that follows the
path of the sun to maximize the solar
radiation incident on the PV surface.
The two most common orientations are (1)
one axis where the array tracks the sun
east to west and (2) two-axis tracking
where the array points directly at the
sun at all times. Tracking arrays use
both the direct and diffuse sunlight.
Two-axis tracking arrays capture the
maximum possible daily energy.
Trailing Edge The
part of a wind energy conversion device
blade, or airfoil, that is the last to
contact the wind.
device which converts the generator's
lowvoltage electricity to
highervoltage levels for transmission
to the load center, such as a city or
electromagnetic device that changes the
voltage of alternating current
electricity. It consists of an induction
coil having a primary and secondary
winding and a closed iron core.
process of sending or moving electricity
from one point to another; usually
defines that part of an electric power
provider's electric power lines from the
power plant buss to the last transformer
before the customer's connection.
(Electric) The movement or transfer of
electric energy over an interconnected
group of lines and associated equipment
between points of supply and points at
which it is transformed for delivery to
consumers or is delivered to other
electric systems. Transmission is
considered to end when the energy is
transformed for distribution to the
Distribution Losses The losses that
result from inherent resistance in
electrical conductors and transformation
inefficiencies in distribution
transformers in a transmission and
Transmission Line A
set of conductors, insulators,
supporting structures, and associated
equipment used to move large quantities
of power at high voltage, usually over
long distances between a generating or
receiving point and major substations or
Transmit high-voltage electricity from
the transformer to the electric
(Electric) An interconnected group of
electric transmission lines and
associated equipment for moving or
transferring electric energy in bulk
between points of supply and points at
which it is transformed for delivery
over the distribution system lines to
consumers or is delivered to other
(of the Economy) The part of the
economy having to do with the how people
and goods are transported (moved) from
place to place.. The transportation
sector is made up of automobiles,
airplanes, trucks, and ships. trains,
Traveling Grate A
furnace grate that moves fuel through
the combustion chamber.
architectural feature used to shade
exterior walls; usually made of a
lattice of metal or wood; often covered
by vines to provide additional
Collector A type of solar thermal
collector in which a heat transfer fluid
drips out of header pipe at the top of
the collector, runs down the collector
absorber and into a tray at the bottom
where it drains to a storage tank.
Triple Pane (Window)
This represents three layers of
glazing in a window with an airspace
between the middle glass and the
exterior and interior panes.
Trombe Wall A wall
with high thermal mass used to store
solar energy passively in a solar home.
The wall absorbs solar energy and
transfers it to the space behind the
wall by means of radiation and by
convection currents moving through
spaces under, in front of, and on top of
True Power The
actual power rating that is developed by
a motor before losses occur.
True South The
direction, at any point on the earth
that is geographically in the northern
hemisphere, facing toward the South Pole
of the earth. Essentially a line
extending from the point on the horizon
to the highest point that the sun
reaches on any day (solar noon) in the
Light) A fluorescent lamp that has a
Tube-In-Plate-Absorber A type of solar
thermal collector where the heat
transfer fluid flows through tubes
formed in the absorber plate.
A type of solar thermal collector that
has tubes (pipes) that the heat transfer
fluid flows through that are connected
to a flat absorber plate.
Tungsten Halogen Lamp
A type of incandescent lamp that
contains a halogen gas in the bulb,
which reduces the filament evaporation
rate increasing the lamp life. The high
operating temperature and need for
special fixtures limits their use to
commercial applications and for use in
projector lamps and spotlights.
Turbine A device
which blades, which is turned by a
force, e.g. that of wind, water , or
high pressure steam. The mechanical
energy of the spinning turbine is
converted into electricity by a
generator. A device for converting the
flow of a fluid (air, steam, water, or
hot gases) into mechanical motion.
that generate electricity when they are
turned by water force, wind, or heat.
Turn Down Ratio The
ratio of a boiler's or gasifier's
maximum output to its minimum output.
Two-Axis Tracking A
solar array tracking system capable of
rotating independently about two axes
(e.g., vertical and horizontal).
Two-Tank Solar System
A solar thermal system that has one
tank for storing solar heated water to
preheat the water in a conventional
Ultimate Analysis A
procedure for determining the primary
elements in a substance (carbon,
hydrogen, oxygen, nitrogen, sulfur, and
Electromagnetic radiation in the
wavelength range of 4 to 400 nanometers.
Underground Home A
house built into the ground or slope of
a hill, or which has most or all
exterior surfaces covered with earth.
Underground Mine A
mine where coal is produced by tunneling
into the earth to the coal bed, which is
then mined with underground mining
equipment such as cutting machines and
continuous, long wall, and short wall
mining machines. Underground mines are
classified according to the type of
opening used to reach the coal, i.e.,
drift (level tunnel), slope (inclined
tunnel), or shaft (vertical tunnel).
Collector A solar thermal collector
that has an absorber that does not have
a glazed covering. Solar swimming pool
heater systems usually use unglazed
collectors because they circulate
relatively large volumes of water
through the collector and capture nearly
80 percent of the solar energy
Conditioner An air conditioner
consisting of one or more assemblies
that move, clean, cool, and dehumidify
Unvented Heater A
combustion heating appliance that vents
the combustion by-products directly into
the heated space. The latest models have
oxygen-sensors that shut off the unit
when the oxygen level in the room falls
below a safe level.
Uranium A heavy,
Uranium Fuel Cycle
The series of steps involved in
supplying fuel for nuclear power
reactors. It includes mining, refining,
the making of fuel elements, their use
in a reactor, chemical processing to
recover spent (used) fuel, reenrichment
of the fuel material, and remaking into
new fuel elements.
Useful Heat Heat
stored above room temperature (in a
solar heating system).
Utility A regulated
entity which exhibits the
characteristics of a natural monopoly
(also referred to as a power provider).
For the purposes of electric industry
restructuring, "utility" refers to the
electric company. "Transmission utility"
refers to the regulated owner/operator
of the transmission system only.
"Distribution utility" refers to the
regulated owner/operator of the
distribution system which serves retail
Generation by electric systems engaged
in selling electric energy to the
Coefficient of Heat Transmission) The
reciprocal of R-Value. The lower the
number, the greater the heat transfer
resistance (insulating) characteristics
of the material.
The deposition of thin films of
semiconductor material by the
evaporation of elemental sources in a
Valence Band The
highest energy band in a semiconductor
that can be filled with electrons.
Vapor Retarder A
material that retards the movement of
water vapor through a building element
(walls, ceilings) and prevents
insulation and structural wood from
becoming damp and metals from corroding.
Often applied to insulation batts or
separately in the form of treated
papers, plastic sheets, and metallic
Turbines Turbines in which the rotor
speed increases and decreases with
changing wind speed, producing
electricity with a variable frequency.
Consumption Vehicle fuel consumption
is computed as the vehicle miles
traveled divided by the fuel efficiency
reported in miles per gallon (MPG).
Vehicle fuel consumption is derived from
the actual vehicle mileage collected and
the assigned MPGs obtained from EPA
certification files adjusted for onroad
driving. The quantity of fuel used by
Vent A component of
a heating or ventilation appliance used
to conduct fresh air into, or waste air
or combustion gases out of, an appliance
or interior space.
Vent Damper A
device mounted in the vent connector
that closes the vent when the heating
unit is not firing. This traps heat
inside the heating system and house
rather than letting it draft up and out
the vent system.
Vent Pipe A tube in
which combustion gases from a combustion
appliance are vented out of the
appliance to the outdoors.
Vented Heater A
type of combustion heating appliance in
which the combustion gases are vented to
the outside, either with a fan (forced)
or by natural convection.
process of moving air (changing) into
and out of an interior space either by
natural or mechanically induced (forced)
That portion of supply air that is drawn
from outside, plus any recirculated air
that has been treated to maintain a
desired air quality.
Vertical Ground Loop
In this type of closed-loop geothermal
heat pump installation, the fluid-filled
plastic heat exchanger pipes are laid
out in a plane perpendicular to the
ground surface. For a vertical system,
holes (approximately four inches in
diameter) are drilled about 20 feet
apart and 100 to 400 feet deep. Into
these holes go two pipes that are
connected at the bottom with a U-bend to
form a loop. The vertical loops are
connected with horizontal pipe (i.e.,
manifold), placed in trenches, and
connected to the heat pump in the
building. Large commercial buildings and
schools often use vertical systems
because the land area required for
horizontal ground loops would be
prohibitive. Vertical loops are also
used where the soil is too shallow for
trenching, or for existing buildings, as
they minimize the disturbance to
landscaping. Also see closed-loop
geothermal heat pump systems.
Turbine (VAWT) A type of wind turbine
in which the axis of rotation is
perpendicular to the wind stream and the
Transmittance The amount of visible
light that passes through the glazing
material of a window, expressed as a
The visible portion of the
electromagnetic spectrum with
wavelengths from 0.4 to 0.76 microns
VMT Vehicle miles
Energy produced from volcanic action.
Volt A unit of
electrical force equal to that amount of
electromotive force that will cause a
steady current of one ampere to flow
through a resistance of one ohm.
Volt (V) The volt
is the International System of Units
(SI) measure of electric potential or
electromotive force. A potential of one
volt appears across a resistance of one
ohm when a current of one ampere flows
through that resistance. Reduced to SI
base units, 1 V = 1 kg times m2 times
s3 times A1 (kilogram meter squared
per second cubed per ampere).
Voltage The amount
of electromotive force, measured in
volts, that exists between two points.
difference in electrical potential
between any two conductors or between a
conductor and ground. It is a measure of
the electric energy per electron that
electrons can acquire and/or give up as
they move between the two conductors.
Electricity produced by chemical action.
Volt-Ampere A unit
of electrical measurement equal to the
product of a volt and an ampere.
Wafer A thin sheet
of semiconductor (photovoltaic material)
made by cutting it from a single crystal
Wall A vertical
structural element that holds up a roof,
encloses part or all of a room, or
stands by itself to hold back soil.
The geographical direction that the
primary or largest exterior wall of a
solid waste, landfill gas, methane,
digester gas, liquid acetonitrile waste,
tall oil, waste alcohol, medical waste,
paper pellets, sludge waste, solid
byproducts, tires, agricultural
byproducts, closed loop biomass, fish
oil, and straw. Waste Energy Municipal
solid waste, landfill gas, methane,
digester gas, liquid acetonitrile waste,
tall oil, waste alcohol, medical waste,
paper pellets, sludge waste, solid
byproducts, tires, agricultural
byproducts, closed loop biomass, fish
oil, and straw used as fuel.
Water Cycle Water
constantly moves through a vast global
cycle, in which it evaporates from lakes
and oceans, forms clouds, precipitates
as rain or snow, then flows back to the
ocean. The energy of this water cycle,
which is driven by the sun, is tapped
most efficiently with hydropower.
Water Heater An
automatically controlled, thermally
insulated vessel designed for heating
water and storing heated water at
temperatures less than 180 degrees
Water Jacket A heat
exchanger element enclosed in a boiler.
Water is circulated with a pump through
the jacket where it picks up heat from
the combustion chamber after which the
heated water circulates to heat
distribution devices. A water jacket is
also an enclosed water-filled chamber in
a tankless coiled water heater. When a
faucet is turned on water flows into the
water heater heat exchanger. The water
in the chamber is heated and transfers
heat to the cooler water in the heat
exchanger and is sent through the hot
water outlet to the appropriate faucet.
Water Source Heat
Pump A type of (geothermal) heat pump
that uses well (ground) or surface water
as a heat source. Water has a more
stable seasonal temperature than air
thus making for a more efficient heat
Water Turbine A
turbine that uses water pressure to
rotate its blades; the primary types are
the Pelton wheel, for high heads
(pressure); the Francis turbine, for low
to medium heads; and the Kaplan for a
wide range of heads. Primarily used to
power an electric generator.
Water Wall An
interior wall made of water filled
containers for absorbing and storing
Water Wheel A wheel
that is designed to use the weight
and/or force of moving water to turn it,
primarily to operate machinery or grind
Watt A metric unit
of power, usually used in electric
measurements, which gives the rate at
which work is done or energy used. The
rate of energy transfer equivalent to
one ampere under an electrical pressure
of one volt. One watt equals 1/746
horsepower, or one joule per second. It
is the product of Voltage and Current
Watt-hour A unit of
electricity consumption of one Watt over
the period of one hour.
Wattmeter A device
for measuring power consumption.
Wave Form The shape
of the phase power at a certain
frequency and amplitude.
Wave Power The
concept of capturing and converting the
energy available in the motion of ocean
waves to energy.
distance between similar points on
successive waves. The distance, measured
in the direction of progression of a
wave, from any given point to the next
point in the same phase.
Caulking and weatherstripping to reduce
air infiltration and exfiltration
into/out of a building.
material used to seal gaps around
windows and exterior doors.
Well A hole drilled
in the earth for the purpose of (1)
finding or producing crude oil or
natural gas; or (2) producing services
related to the production of crude or
Wellhead The point
at which the crude (and/or natural gas)
exits the ground.
process of transmitting electricity over
one or more separately owned electric
transmission and distribution systems.
(See Wholesale and Retail Wheeling.)
Whole House Fan A
mechanical/electrical device used to
pull air out of an interior space;
usually located in the highest location
of a building, in the ceiling, and
venting to the attic or directly to the
The wheeling of electric power in
amounts and at prices that generally
have been negotiated in long term
contracts between the power provider and
a distributor or very large power
Wind The term given
to any natural movement of air in the
atmosphere. A renewable source of energy
used to turn turbines to generate
Wind Energy Energy
available from the movement of the wind
across a landscape caused by the heating
of the atmosphere, earth, and oceans by
Conversion System (WECS) or Device An
apparatus for converting the energy
available in the wind to mechanical
energy that can be used to power
machinery (grain mills, water pumps) and
to operate an electrical generator.
Wind Generator A
WECS designed to produce electricity.
Devices powered by the wind that produce
mechanical or electrical power.
Wind Power Plant A
group of wind turbines interconnected to
a common power provider system through a
system of transformers, distribution
lines, and (usually) one substation.
Operation, control, and maintenance
functions are often centralized through
a network of computerized monitoring
systems, supplemented by visual
inspection. This is a term commonly used
in the United States. In Europe, it is
called a generating station.
Assessment The process of
characterizing the wind resource, and
its energy potential, for a specific
site or geographical area.
Wind Rose A diagram
that indicates the average percentage of
time that the wind blows from different
directions, on a monthly or annual
Wind Speed The rate
of flow of the wind undisturbed by
Wind Speed Duration
Curve A graph that indicates the
distribution of wind speeds as a
function of the cumulative number of
hours that the wind speed exceeds a
given wind speed in a year.
Wind Speed Frequency
Curve A curve that indicates the
number of hours per year that specific
wind speeds occur.
Wind Speed Profile
A profile of how the wind speed changes
with height above the surface of the
ground or water.
Wind Tower Devices,
some as tall as 120 feet, which lift
wind turbine blades high above the
ground to catch stronger wind currents.
Wind Turbine A term
used for a wind energy conversion device
that produces electricity; typically
having one, two, or three blades.
Wind Turbine Rated
Capacity The amount of power a wind
turbine can produce at its rated wind
speed, e.g., 100 kW at 20 mph. The rated
wind speed generally corresponds to the
point at which the conversion efficiency
is near its maximum. Because of the
variability of the wind, the amount of
energy a wind turbine actually produces
is a function of the capacity factor
(e.g., a wind turbine produces 20% to
35% of its rated capacity over a year).
Wind Velocity The
wind speed and direction in an
Windmill A WECS
that is used to grind grain, and that
typically has a high-solidity rotor;
commonly used to refer to all types of
Window A generic
term for a glazed opening that allows
daylight to enter into a building and
can be opened for ventilation.
Windpower Curve A
graph representing the relationship
between the power available from the
wind and the wind speed. The power from
the wind increases proportionally with
the cube of the wind speed.
The change in the power available in the
wind due to changes in the wind speed or
velocity profile; the windpower profile
is proportional to the cube of the wind
Wingwall A building
structural element that is built onto a
building's exterior along the inner
edges of all the windows, and extending
from the ground to the eaves. Wingwalls
help ventilate rooms that have only one
exterior wall which leads to poor cross
ventilation. Wingwalls cause
fluctuations in the natural wind
direction to create moderate pressure
differences across the windows. They are
only effective on the windward side of
Wire (Electrical) A
generic term for an electrical
Natural Gas Company
Wood and Waste (as
used at electric utilities) Wood
energy, garbage, bagasse (sugarcane
residue), sewerage gas, and other
industrial, agricultural, and urban
refuse used to generate electricity for
Wood Energy Wood
and wood products used as fuel,
including round wood (cord wood), limb
wood, wood chips, bark, sawdust, forest
residues, charcoal, pulp waste, and
spent pulping liquor.
Wood Stove A
wood-burning appliance for space and/or
water heating and/or cooking.
Working Fluid A
fluid used to absorb and transfer heat
Wound Rotor Motors
A type of motor that has a rotor with
electrical windings connected through
slip rings to the external power
circuit. An external resistance
controller in the rotor circuit allows
the performance of the motor to be
tailored to the needs of the system and
to be changed with relative ease to
accommodate system changes or to vary
the speed of the motor.
Public Power Supply System
State Department of Transportation
State Energy Office (now Energy Policy
Division of CTED)
Utilities and Transportation Commission
Yaw The rotation of
a horizontal axis wind turbine around
its tower or vertical axis.
Yellowcake A natural
uranium concentrate that takes its name
from its color and texture. Yellowcake
typically contains 70 to 90 percent U3O8
(uranium oxide) by weight. It is used as
feedstock for uranium fuel enrichment
and fuel pellet fabrication.
Yurt An octagonal
shaped shelter that originated in
Mongolia, and traditionally made from
leather or canvas for easy
Zone An area within
the interior space of a building, such
as an individual room(s), to be cooled,
heated, or ventilated. A zone has its
own thermostat to control the flow of
conditioned air into the space.
combining of rooms in a structure
according to similar heating and cooling
patterns. Zoning requires using more
than one thermostat to control heating,
cooling, and ventilation equipment.
Credits: Washington State
Department of Community, Trade &
Economic Development (http://www.cted.wa.gov/portal/alias__CTED/lang__en/tabID__541/DesktopDefault.aspx)
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