Solar thermal systems make use of the large amount of solar irradiation that hits the earth’s surface every year. Solar irradiation in the U.K varies from approximately 900 kWh/m²/yr to 1,200 kWh/m²/yr, depending on location.
Solar thermal panels mounted on the roof of a building transfer heat from the available solar radiation to a heat transfer medium, usually water or a water/antifreeze mixture, through a system of heat conducting tubes arranged in the solar collector.
In the U.K. solar thermal systems are mainly used for domestic hot water, and are used with a dual coil cylinder. This allows heat from a boiler to be used to supplement the solar thermal system during the winter months and at night. A well designed solar thermal system can supply 60% of a buildings hot water requirement over the year.
Ideally a solar thermal system needs to be mounted on a south facing roof, with minimal shading and at an angle of inclination of 30º to the horizontal. Other orientations and pitches are possible, although these do lead to slight reductions in collector efficiency.
Solar thermal provides emission free hot water, and depending on the fuel displaced can offer substantial cost and CO2 savings. It is a well established technology, with a large number of suppliers offering systems in the U.K., and is an excellent measure to reduce carbon emissions.