Energy from the sun can be used in three main ways, and when talking about solar energy, it is important to distinguish between these three types:
The basic principle common to all solar thermal systems is simple: solar radiation is collected and the resulting heat conveyed to a heat transfer medium - usually a fluid but also air in the case of air collectors. The heated medium is used either directly - for example to heat swimming pools - or indirectly, by means of a heat exchanger which transfers the heat to its final destination - for instance: space heating.
Solar thermal can be successfully applied to a broad range of heat requirements including domestic water heating, space heating, and drying. New exciting areas of applications are being developed in particular solar assisted cooling. System design, costs and solar yield are being constantly improved.
Photovoltaic systems use cells to convert solar radiation into electricity. The cell consists of one or two layers of a semi-conducting material. When light shines on the cell it creates an electric field across the layers, causing electricity to flow. The greater the intensity of the light, the greater the flow of electricity is.The most common semi conductor material used in photovoltaic cells is silicon, an element most commonly found in sand. There is no limitation to its availability as a raw material; silicon is the second most abundant material in the earth’s mass.A photovoltaic system therefore does not need bright sunlight in order to operate. It can also generate electricity on cloudy days.
Sources: European Photovoltaic Industry Association: www.epia.orgEuropean Solar Thermal Industry federation: www.estif.org