GLOSSARY OF SOLAR TERMINOLOGY
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ABSORBER: The heat absorber is the part of the solar collector which receives radiant energy from the sun and transforms it into thermal energy.  It is usually made of metal that is coated with a heat-absorbing material.
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ACTIVE SYSTEM:  An active solar energy system uses either liquid or air to transport heat to the point of use.  It is comprised of collectors to absorb the sun's solar energy; pumps, pipes, blowers and/or ducts to transport the energy, a heat storage area, controls and valves.  An active system can be installed during construction or retrofitted into an existing structure.
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COLLECTOR: A collector is the part of a system that collects and absorbs the heat of the sun and, in turn, heats a fluid or air.
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EXPANSION TANK:  A small tank that compensates for liquid expansion in a fluid system.
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GLAZING: The transparent covering on the collector, usually glass or plastic.
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HEAT EXCHANGER: This is a device for transferring heat energy from one medium to another.  In a solar energy system as heated fluid or air from the collector passes through the heat exchanger, it transfers its heat load for immediate use or storage.
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HYDRONIC SYSTEM:  A closed loop heating system utilizing the solar-heated hot water.
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INSOLATION: The rate of solar radiation received.
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INSULATION: Material used to reduce heat loss on exposed piping and through the wall of collector assemblies, water heaters and storage tanks.
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MIXING VALVE:  A valve which automatically mixes hot and cold water to meet a controlled temperature setting.
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PASSIVE SYSTEMS:  A passive solar energy system utilizes the design of the structure to collect, store and transmit solar heat.  It maximizes the use of natural convection, conduction and radiation while minimizing the use of mechanical devices powered by conventional fuel.
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PUMP: In active solar space heating and water heating systems, small electric pumps are required to move the heat transfer fluid through the system and back to the collector.
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STORAGE: Storage of solar heat is necessary to meet energy demands during non-sunny hours.  Heat storage is accomplished by properly sized hot liquid storage tanks, heating rocks in a large storage bin, or eutectic salt storage.
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TILT ANGLE: The angle from horizontal that the collector is tilted to provide maximum exposure to the sun.  This angle is determined by geographic location and any seasonal variations in the projected use of solar energy.  (Pool heating in the spring and fall, space heating in the winter months)
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TRANSFER MEDIUM:  The liquid or air used to transport solar heat.

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