Active Solar Heating
There
are two basic types of active solar heating systems based on the type of
fluid—either liquid or air—that is heated in the solar energy
collectors. (The collector is the device in which a fluid is heated by the
sun.) Liquid-based systems heat water or an antifreeze solution in a
"hydronic" collector, whereas air-based systems heat air in an
"air collector."
Both of these systems collect and absorb solar radiation, then transfer the solar heat directly to the interior space or to a storage system, from which the heat is distributed. If the system cannot provide adequate space heating, an auxiliary or back-up system provides the additional heat. Liquid systems are more often used when storage is included.