GLOSSARY OF TERMS: Renewable Energy

Dec. 9, 2008

Test your renewable energy know-how with these terms and definitions from the U.S. Renewable Energy Association.

ABSORBER: The 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 holes).

BAGHOUSE: An air pollution control device used to filter particulates from waste combustion gases; a chamber containing a bag filter.

BLACKBODY: An ideal substance that absorbs all radiation falling on it and reflects nothing.

CLIMATE CHANGE: A term used to describe short and long-term effects on the Earth”s climate as a result of human activities, such as fossil fuel combustion and vegetation clearing and burning.

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 system.

DIRECT GAIN: The process by which sunlight directly enters a building through the windows and is absorbed and stored in massive floors or walls.

EARTH BERM: A mound of dirt next to exterior walls to provide wind protection and insulation.

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.

GOVERNOR: A device used to regulate motor speed, or, in a wind energy conversion system, to control the rotational speed of the rotor.

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.

HELIOTHERMAL: Any process that uses solar radiation to produce useful heat.

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 power demand.

LANDSCAPING: Features and vegetation on the outside of or surrounding a building for aesthetics and energy conservation.

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.

ONE SUN: The maximum value of natural solar insulation.

SOLAR FRACTION: The percentage of a building”s seasonal energy requirements that can be met by a solar energy device(s) or system(s).

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.

This glossary of terms was abstracted from a resource compiled by the U.S. Department of Energy’s Energy Efficiency & Renewable Energy group (

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