 Glossary
Confused with technical jargon? This section contains a list of commonly used technical words related to renewable energy or the environment. A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z AC - in electricity, alternating current. Most electrical appliances use AC electricity. Active Solar Water Heater - A device using solar energy to heat water and requiring external power such as electricity to run a pump to circulate the water. Alternating Current - Electric current in which the flow of electrons reverses at regular and recurring intervals. In the U.S. the alternating frequency is 60 cycles per second. Ampere - Abbreviate Amp. A standard unit for measuring electric current. Array - A small group of solar thermal collectors or photovoltaic panels placed together. Atrium - A closed interior court with a glazed roof to which other rooms in a building open. Often it is used to collect passive solar heat. Batch Water Heater - A passive solar water heater in which water is heated and stored for later use in a tank. Berm - a mound of earth either abutting a building wall to help stabilize inside building temperature or positioned to deflect wind from the building. British Thermal Unit (BTU) - A unit of heat equal to the amount needed to raise one pound of water one degree Fahrenheit. Clerestory - Windows placed high in the wall near eaves or vertically over the roof for light, heat and ventilation. Composting toilet - A waterless sewage recycling system which decomposes human excreta, and other organic materials such as leaves to create a humus. Cord - A unit of measurement for firewood. It is a stack four ft. high, four ft. deep and eight ft. wide. Direct Current (DC) - Electric current which flows in one direction. Direct Gain System - Passive solar heating system in which sun directly penetrates and warms a building's interior. A building with south-facing windows and thermal mass to absorb the solar gain. Domestic Hot Water (DHW) - A water heating system used to supply household hot water needs for bathing, washing clothes. etc. Double-Glazing - Two panes of glass or other transparent material mounted parallel to each other within a frame, enclosing a dead air space to create an insulating barrier to heat flow. Electric Current - The "volume" of electron flow in an electric circuit. Measured in Amperes. Energy Storage - The ability to hold energy for later retrieval. In solar devices this is typically either heat storage in thermal mass or electric storage in batteries or the power grid. Evaporative Cooling - A means of temperature reduction which operates on the principle that water absorbs latent heat from the surrounding air when it evaporates. Flat Plate Collector - A solar collector in which the absorber is a flat or nearly flat surface. Typically, it is comprised of an insulated box or enclosure, one or more layers of glazing and an absorber. Pipes or ducts deliver the heat transfer fluid to and from the collector to the storage and distribution components of the systems. Glazing - A covering of transparent or translucent materials, usually glass or plastic, used for admitting light. Heat Exchanger - A device used to transfer heat from a fluid flowing on one side of a barrier to a fluid or fluids flowing on the other side without bringing the two fluids into direct contact. Many solar heating systems use heat exchangers. Heating Load - The rate of heat gain required to maintain indoor comfort; measured in BTU's per hour. Heat Pump - A mechanical device that transfers heat from one medium, the heat source, to another, the heat sink thereby cooling the first and warming the second. Indirect Gain System - Passive solar heating system in which the sun directly warms a heat storage medium in an area of the building, and heat then is distributed from the medium to the rest of the building by natural convection, conduction or radiation. Insulation - A material with a high resistance to heat flow. Many kinds of insulation are available. Inverter - A device which converts direct current (DC) electricity to alternating current. Kilowatt - A unit of electrical power equal to one thousand watts in one hour. Symbolized kW and equal to 3,413 BTU/hour or about 1 l/3 Horsepower. Orientation - The direction that a building or solar collector faces. Panel - (1) A solar collector. (2) A photovoltaic module. Passive Solar Water Heater - A solar water heater which operates exclusively on the energy of the sun, without the aid of any supplemental energy to run pumps, fans or other devices. The two most common types are batch solar water heaters and thermosiphon water heaters. Payback Period - In economic analysis, the amount of time it takes for a solar system or component to pay for itself in fuel savings. Photovoltaic Cell - The smallest device capable of converting sunlight directly to direct current electricity. Photovoltaic Effect - The process by which sunlight generates electricity in a photovoltaic cell. The cell has several layers. The back of the cell is commonly made of crystalline silicon, doped with a chemical that creates positively charged spaces or "holes" in the crystalline structure. The front of the cell is doped with a chemical that creates an abundance of negatively charged electrons. When sunlight passes through the front layer, the added energy knocks "loose" some of the electrons, which jump to the positively charged "holes." The movement of electrons is the flow of electricity and this can be channeled away through thin wires embedded in the cell. Photovoltaic System - A complete set of components for converting sunlight to electricity, storing that electricity and delivering it to its end use. Power - The conversion of energy over time, usually to work. Commonly expressed in units of energy per unit of time, e.g., BTU/hour, Watts, Horsepower. Propane - A gaseous hydrocarbon of the methane series. It is stored as a liquid in pressurized tanks and burned as a gas at atmospheric pressure. Retrofitting - The application of a solar heating or cooling system to an existing building. R-Value - A unit for measuring the insulating value of a substance, or its resistance to heat flow. Skylight - A window placed in the roof of a building, typically mounted horizontally or near to horizontal. Solar - Of, derived from or relating to the sun especially as affecting the earth. Utilizing the sun's rays. Solar Access - The ability of sunlight to reach a solar collector unimpeded by trees, fences, buildings, or other obstruction. Solar Cell - The basic photovoltaic device which generates electricity when exposed to sunlight. Solar Collection - The absorption of sunlight with the intent of applying the energy thus generated to a certain task. Solar Cooling - Cooling that is either powered mechanically by solar energy or accomplished through passive design elements that keep a building cooler than it would otherwise be. Solar Easement - An agreement between property owners whereby one grants the other the use of his/her solar right or access to sunlight. Solar Energy - Electromagnetic radiation emitted by the sun. Each day, the sun sends 400 million times the amount of energy to earth than humans use. Viewed in this context, it becomes apparent that with ingenuity and effort, we can provide all of our energy needs in a gentle, environmentally sound way by using a small fraction of what the sun has to offer. Solar Hot Water - Water heated by the sun. Solar House - A residence whose primary heating source is the sun. Solar Oven - An insulated enclosure with a glazed surface that reaches 300 to 400 degrees F. in full sun and is used for cooking. Space Heating - Heating of an interior space. Storage Capacity - In a solar system, the amount of energy that the storage device can hold under normal operating conditions. Sunspace - A living space enclosed by glazing. A solarium or greenhouse designed more for people than for plants. Thermal Mass - Materials such as concrete, brick, adobe, stone and water which can readily absorb, store and release a lot of heat. Thermal Storage - The absorption and subsequent release of heat. Thermal Storage Wall - A wall made of massive materials that can absorb, store, transmit and release large amounts of heat and is covered on the exterior with a glazing. Typically made of brick, cement filled concrete or cinder block, adobe, cement, or containers full of water. Thermosiphon Air Panel (TAP) - A hot air collector typically mounted vertically on the wall of a frame construction or other low mass structure to provide daytime space heating. Heat is delivered in this system by natural convection. Tracker - A device upon which a solar collector is mounted and which moves throughout the day to keep the collectors pointed directly at the sun. Trombe Wall - One kind of thermal storage wall named after its French inventor, Felix Trombe. It is comprised of a masonry wall covered on the outside with glazing. Sunlight passing through the glazing generates heat which conducts through the wall. Warm air between the glazing and the Trombe wall surface can also be channeled by natural convection into the building interior or to the outside, depending on the building's heating or cooling needs. Watt - The unit of work in an electric circuit. It equals the flow of one Ampere at a pressure of one volt. One watt equals l/746 horsepower. Source: The American
Solar Energy Society (ASES)
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