1. Solar thermal systems in Finland

Solar collectors transform solar radiation into thermal energy that can be used for domestic or industrial heating purposes. Solar thermal systems are a good match also for Finland, because warm water is consumed throughout the year. Solar thermal heat can be used to warm up domestic water supplies throughout the year and from spring to fall solar thermal systems can also be used to warm up living spaces. For example bathroom and shower spaces often require heating all year round. Storage systems are an essential component of solar thermal systems. The storing options vary according to the scale of the uitilization: private households usually have water boiler based storage systems whereas district heating -sized systems use heat liquid based heat batteries at the size of a swimming pool or underground caves. Finnish climate conditions require hybrid heating system that use several sources of energy. In addition to solar energy, for example heat pumps, fireplaces, bio energy, oil or district heating can be used as supportive sources of energy for solar thermal systems. Combining solar thermal collectors to a heat pump system may double the heat pump efficiency and lengthens the system life cycle.  The Coefficient of Performance (COP) rating of a heat pump system can be doubled by integrating solar thermal collectors to a heat pump system. COP-rating depicts the ratio of consumed electricity into produced heat. Solar collector reduces the active hours on heat pump systems and the number of starts. This lengthens the lifetime of for example ground heat system compressor (price ~5000€) when it normally should be replaced every 10-15 years.