Glossary of Solar Radiation Resource Terms

Other relevant glossaries


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Heating Degree-Days - the amount of building heating needed, created by adding up all temperature differences of the form ( 65°F - daily temperature in °F ) for each day in which the temperature falls below 65°F.


Heliostat - a large flat mirror, usually on a tracker so that it can continuously reflect the sun's rays onto a central receiver. A typical central receiver system requires hundreds of heliostats.


Humidity - the amount of water vapor in the air. Because the common measure of water vapor is the ratio between the measured amount and the maximum possible amount (the saturation point at which water condenses as dew), humidity and relative humidity are generally used interchangeably.


Hybrid System - a heating system or energy generator that does not rely on one exclusive energy source. For example, many domestic photovoltaic systems use gasoline generators as backup systems during periods of extreme cloudiness. Utility-scale hybrid solar thermal power plants use sunlight to boil water, and an alternative energy source such as natural gas when there is insufficient sunlight.


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