Haboob |
A squall of billowing dust that blows across the Syrian Desert when a monsoon collides with dry air currents above it. |
Halogen Lamp |
A special type of incandescent globe made of quartz glass and a tungsten filament, enabling it to run at a much higher temperature than a conventional incandescent globe. Efficiency is better than a normal incandescent, but not as good as a fluorescent light. |
Harmattan |
A very hot wind with dangerous cross-currents that blows southwest from central Africa and across the Sudan, typically December through February. It is often preceded by “the smokes,” clouds of stinging, red dust. |
Harmonic Content |
Frequencies in the output waveform in addition to the primary frequency (usually 50 or 60 Hz.) Energy in these harmonics is lost and can cause undue heating of the load. |
H-Coal Process |
A means of making coal cleaner so it will produce less ash and less sulfur emissions. |
Head |
The difference in elevation between two parts of a liquid-based system. In hydro power, the difference between a source of water and the location at which the water from that source may be used (synonym vertical drop). With pumps, the vertical distance the pump must move the water. |
Headrace |
A flume or channel that feeds water into a hydro turbine. |
Health Spa |
an establishment (often commercial) which is visited by guests seeking therapy and relaxation; many center around hot mineral springs or use hot water from geothermal wells. |
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 Exchanger |
a device in which heat is transferred by conduction through a metal barrier from a hotter liquid or gas, to warm a cooler liquid or gas on the other side of the metal barrier. Types of heat exchangers include "shell and tube," and "plate." |
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 exfiltration of warm air. |
Heat Pump |
A device typically used for heating and cooling of buildings by drawing from or dissipating into the ambient temperature of air or water. When cooling, a heat pump works like a refrigerator. When heating, it also works like a fridge, except the heat produced is used to heat a space. |
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 Sink |
A medium or container to which heat flows. Thermal mass walls and floors in a passive solar home act as a heat sink during the day. |
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 |
Heat is transferred from one substance or location to another by three methods—radiation, convection and conduction. The sun’s rays are a good example of radiation; warm air rising is heat movement by convection; and touching a hot iron or frying pan with your hand is heat transfer by conduction. |
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 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. |
Helm Wind |
A wind that blows down the slopes of small, smooth hills. Helm winds are common in the British Isles. |
Hertz |
The frequency of electrical current described in cycles per second. |
Hertz (Hz) |
A measure of the number of cycles or wavelengths of electrical energy per second. The United States electricity supply has a standard frequency of 60 hertz. |
Heterojunction |
A region of electrical contact between two different materials. |
High Voltage Disconnect |
The voltage at which a charge controller will disconnect the photovoltaic array from the batteries to prevent overcharging. |
High Voltage Disconnect Hysteresis |
The voltage difference between the high voltag disconnect set point and the voltage at which the full photovoltaic array current will be reapplied. |
High-Sulfur Coal |
Coal whose weight is more than one percent sulfur. |
Hms:O |
The unit of measurement of the electrical resistance of a material to the flow of current. |
Hole |
The vacancy where an electron would normally exist in a solid; behaves like a positively charged particle. |
Homojunction |
The region between an n-layer and a p-layer in a single material, photovoltaic cell. |
Horizontal-Axis Wind Turbines |
Turbines on which the axis of the rotor’s rotation is parallel to the wind stream and the ground. |
Horsepower |
A measure of the capacity to generate energy or do work. 1 horsepower = 746 watts. |
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) |
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. |
Hot Spot |
A phenomenon where one or more cells within a PV module or array act as a resistive load, resulting in local overheating or melting of the cells. |
Hot Springs |
a natural spring that puts out water warmer than body temperature and therefore feels hot; may collect in pools or flow into streams an lakes. A geothermal phenomenon. |
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 |
Hub |
The center mount for the blades. Laser cut like mine are hard to beat. |
HVAC (Heating Ventilation And Air Conditioning) |
A system that provides heating, ventilation and/or cooling within or associated with a building. |
Hybrid System |
A PV system that includes solar PV and some other electricity generating power source. |
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. |
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. |
Hydroelectricity |
Electric energy made by the conversion of energy produced from running water. |
Hydro-Electricity |
Any electricity that is generated by the flow of water. |
Hydrogen Fuel Cell |
A device that converts hydrogen to DC electricity. |
Hydrogenated 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 freely. |
Hydrometer |
A hydrometer is an instrument for measuring the density of liquids in relation to the density of water. The hydrometer is used to indicate the state of charge in lead-acid cells by measuring the specific gravity of the electrolyte. |
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. |
Hydronic Heating System |
A type of heating system where water is heated in a solar collector or boiler, and is pumped to heat exchangers or radiators in rooms. Radiant floor systems have a grid of tubing laid out in the floor for distributing the heat. Temperature of the space is controlled by regulating the flow and/or temperature of the circulating water. |
Hydropower |
captures the energy in flowing water and uses it to generate electricity. |
Hydrothermal |
hydro means water and thermal means heat. Literally hydrothermal means hot water. Steam and hot water reservoirs are hydrothermal reservoirs. Hot dry rock resources and magma resources are not considered to be hydrothermal resources. |
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. |