Solar-Water In its standard version – certified with the Solar Keymark – the Linear Mirror heats water up to 100 °C, also in winter. It is used for heating building, or for heating sanitary water. For instance a hotel at Pordenone has been using it since 2014 without any problems. The solar-water heat exchanger is a high quality swiss product from Energie Solaire. Its integration in the existing heating system of buildings is very easy.