Solar Thermal Energy is a system which traps the heat from the sun and uses it, either for heating water, or in some cases for producing electricity. It is to be distinguished from Photovoltaic solar energy, which is a system where the panels convert the sun's energy into electricity themselves.
These are the sort of solar panels that are sometimes found at the bottom of a swimming pool. They are also sometimes used to heat rooms. Air or water is used to transfer the heat that the panel stores into the space or pool which is to be heated. The amount of heat trapped is not enormous. They are also often used in ventilation (HVAC) systems in offices and homes. This is especially common in the USA.
Medium heat panels are able to produce enough heat to heat water for domestic hot water needs. It will cost up to £10,000 for the average household to install a solar thermal energy system, and they can hope to be able to heat up to 50% of their hot water using this method. These systems can also be used to distill clean drinking water in areas where there is no good supply of clean water.
Solar thermal energy (STE) is a technology for harnessing solar energy for thermal energy (heat). Solar thermal collectors are classified by the United States Energy Information Administration as low-, medium-, or high-temperature 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 heating water or air for residential and commercial use. High-temperature collectors concentrate sunlight using mirrors or lenses and are generally used for electric power production. STE is different from and much more efficient than photovoltaics, which converts solar energy directly into electricity. While existing generation facilities provide only 600 megawatts of solar thermal power worldwide in October 2009, [note 1] plants for an additional 400 megawatts are under construction and development is underway for concentrated solar power projects totalling 14,000 megawatts.