Active solar thermal systems collect solar radiation to heat air and/or water for domestic, commercial, or industrial use. The collector for a solar hot water system is typically a 4 ft. x 8 ft. box structure that has a glass top with a black absorber underneath it to circulate water. As the water is pumped through the collector, it is warmed and then circulated through a large, insulated tank inside a building. The warmed water can then be used to provide heat or hot water to the building. A solar hot water system can comprise one or more solar collectors, which are mounted on either a pitched, south-facing roof or on the ground. A solar water heater can offer a cost-effective way to produce hot water. The DOE's "Energy Savers" website outlines the types of solar water heaters available and can help you assess the best system for your home or business.
A solar air heating system uses the sun's energy to heat air. The indoor air is drawn through the collector, which heats the air up to an additional 30 degrees. A small fan pushes the warmed air back into the building. The DOE's "Energy Savers" website provides a complete overview on the types, benefits, and maintenance of active solar heating systems