Introduction

Solar thermal energy is based on the conversion of short-wave solar radiation into thermal energy.

The functional principle of a solar thermal system is as follows: Solar radiation is absorbed by an absorber material, usually metals such as copper and aluminium, and converted into heat. The thermal energy generated is transferred via heat conduction to a heat transfer medium circulating in pipes. The heat transfer medium is thus heated as it flows through the collector and then fed to a storage tank so that hot water is available even at times when there is no solar radiation.

This way of generating heat is suitable for detached houses or, in the case of larger collector arrays, for feeding into a local or district heating network as well as for solar process heat and solar cooling.

The most common application is still in the private sector, with typical collector areas of 6 m2 for solar systems for hot water production and 15 to 20 m2 for combined systems (in single-family homes). These systems normally cover 40 to 80 % of the annual hot water demand. At the end of 2010, approximately 4.5 million square metres of solar collectors with a total output of 3,191 MWth were installed in Austria. (Weiss/Eberl 2011)