The potential of solar energy in Finland is high. The solar radiation on a horizontal level is annually approximately 800 kWh/m2. Solar radiation is basically pure exergy. The problem is the low power density and for heating purposes the time difference between the maximum of solar energy input (summer) and the maximum heat demand (winter). Therefore, an effective exploitation of solar energy also requires high-performance thermal storage systems.
Solar heating provides thus also for Finland a possibility to produce part of the annual energy needs. This option is also a must in the future, because the use of renewable energy in buildings must be added due to the European commitments. Solar heating has been used for a long time for hot water heating and partly also for heating of premises. In Finland the nearly inscrutable option is to use solar heating in producing energy for district heating networks. In these it is possible to use concentrating solar collectors and to achieve so high temperatures that the energy can be supplied into supply duct.