Glossary of Energy Terms

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A B C D E F G H I J K L M N O P Q R S T U V W X-Z Acronyms

Note: No entries for Y or Z.

Letter H

H-COAL PROCESS - A means of making coal cleaner so it will produce less ash and less sulfur emissions.


HEAT BALANCE - The outdoor temperature at which a building's internal heat gain (from people, lights and machines) is equal to the heat loss through windows, roof and walls.

HEAT CAPACITY - The amount of heat necessary to raise the temperature of a given mass one degree. Heat capacity may be calculated by multiplying the mass by the specific heat.

HEAT ENGINE - An engine that converts heat to mechanical energy.

HEAT GAIN - an increase in the amount of heat contained in a space, resulting from direct solar radiation, heat flow through walls, windows, and other building surfaces, and the heat given off by people, lights, equipment, and other sources.

HEAT LOSS - A decrease in the amount of heat contained in a space, resulting from heat flow through walls, windows, roof and other building surfaces and from ex-filtration of warm air.

HEAT PUMP - An air-conditioning unit which is capable of heating by refrigeration, transferring heat from one (often cooler) medium to another (often warmer) medium, and which may or may not include a capability for cooling. This reverse-cycle air conditioner usually provides cooling in summer and heating in winter.

HEAT RATE - A number that tells how efficient a fuel-burning power plant is. The heat rate equals the Btu content of the fuel input divided by the kilowatt-hours of power output.

HEAT STORM - Heat storms occur when temperatures exceed 100 degrees Fahrenheit over a large area for three days in a row. Normal hot temperatures cause electricity demand to increase during the peak summertime hours of 4 to 7 p.m. when air conditioners are straining to overcome the heat. If a hot spell extends to three days or more, however, nighttime temperatures do not cool down, and the thermal mass in homes and buildings retains the heat from previous days. This heat build-up causes air conditioners to turn on earlier and to stay on later in the day. As a result, available electricity supplies are challenged during a higher, wider peak electricity consumption period.

HEAT TRANSFER - Flow of heat energy induced by a temperature difference. Heat flow through a building envelope typically flows from a heated, or hot area to a cooled, or cold area.

HEATING DEGREE DAY - A unit that measure the space heating needs during a given period of time.

HEATING LOAD - The rate at which heat must be added to a space in order to maintain the desired temperature within the space.

HEATING SEASONAL PERFORMANCE FACTOR - A representation of the total heating output of a central air-conditioning heat pump in Btus during its normal usage period for heating, divided by the total electrical energy input in watt-hours during the same period, as determined using the test procedure specified in the California Code of Regulations, Title 20, Section 1603(c).

HEATING VALUE - The amount of heat produced by the complete combustion of a given amount of fuel.

HEAVY WATER - A type of hydrogen atom that may be used as fuel for fusion power plants. Also called DEUTERIUM, it is found in abundance in the seas.

HEDGING CONTRACTS - Contracts which establish future prices and quantities of electricity independent of the short-term market. Derivatives may be used for this purpose. (See Contracts for Differences, Forwards, Futures Market, and Options.)

HELIOCHEMICAL - Using solar radiation to cause chemical reactions.

HELIOTHERMAL - A process that uses the sun's rays to produce heat.

HERTZ - A unit of electromagnetic wave frequency that is equal to one cycle per second. - It is named after Henrich R. Hertz.

HIGH-SULFUR COAL - Coal whose weight is more than one percent sulfur.

HOME ENERGY ASSISTANCE PROGRAM (HEAP) - A centrally operated direct payment program that assists eligible households in offsetting the cost of heating and cooling their homes. Payments are generally made in the form of dual party warrants (checks) made payable to the applicant and their designated utility company. The program is administered by the California Department of Economic Opportunity using federal and state funds. The toll-free number for the HEAP Program is (800) 433-4327. For more information about your utility bills.

HORSEPOWER (HP) - A unit for measuring the rate of doing work. One horsepower equals about three-fourths of a kilowatt (745.7 watts).

HOT - (Colloquial) - The word is sometimes used to describe electric utility lines that are carrying electric currently. It also is used to refer to anything that is highly radioactive.

HOT DRY ROCK - A geothermal resource created when impermeable, subsurface rock structures, typically granite rock 15,000 feet or more below the earth's surface, are heated by geothermal energy. The resource is being investigated as a source of energy production.

HSPF (Heating Seasonal Performance Factor) - A measure of heating efficiency for the total heating output of a central air-conditioning heat pump. Efficiency is derived according to federal test methods by using the total Btus during its normal usage period for heating divided by the total electrical energy input in watt-hours during the same period. California Code of Regulations, Section 2-1602(c)(7).

HVAC (Heating Ventilation and Air Conditioning) - A system that provides heating, ventilation and/or cooling within or associated with a building.

HYDROELECTRIC POWER - Electricity produced by falling water that turns a turbine generator. Also referred to as HYDRO.

HYDROELECTRIC SPILL GENERATION - Hydroelectric generation in existence prior to January 1, 1998, that has no storage capacity and that, if backed down, would spill. This term also refers to a hydro resource that has exceeded or has inadequate storage capacity and is spilling, even though generators are operating at full capacity.

HYBRID VEHICLE - Usually a hybrid EV, a vehicle that employs a combustion engine system together with an electric propulsion system. Hybrid technologies expand the usable range of EVs beyond what an all-electric-vehicle can achieve with batteries only.

HYDRONIC HEATING - A system that heats a space using hot water which may be circulated through a convection or fan coil system or through a radiant baseboard or floor system.

HYDROTHERMAL SYSTEMS - Underground reservoirs that produce either dry steam or a mixture of steam and water.

HYGAS - A process that uses water to help produce pipeline-quality gas from coal.

A B C D E F G H I J K L M N O P Q R S T U V W X-Z Acronyms
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