Turning solar energy into heat

Solar thermal energy is a technology for harnessing solar energy for thermal energy (heat). There are different types of solar thermal collectors. Low temperature collectors are flat plates generally used to heat swimming pools. Medium-temperature collectors are also usually flat plates but are used for creating hot water for residential and commercial use. High-temperature collectors concentrate sunlight using mirrors or lenses and are generally used for electric power production.

Solar thermal systems are usually composed of solar thermal collectors, a fluid system to move the heat from the collector to its point of usage. The systems may be used to heat water for a wide variety of uses, including home, business and industrial uses.  In many regions of the world, a solar hot water system can provide up to 85% of domestic hot water energy. In northern European countries, combined hot water and space heating systems are used to provide 15% to 25% of home heating energy.

In order to heat water using solar energy, a collector is fastened to the roof of a building, or on a wall facing the sun. In some cases, the collector may be free-standing. The working fluid is either pumped (active system) or driven by natural convection (passive system) through it.