These glazed flat-plate solar collectors are now obligatory with all new construction projects in Catalonia. They function by pumping a heat transfer fluid through the solar panel which is heated up by the sun. This liquid, normally water with an antifreeze additive, is then used to heat water in a storage tank. This water is then available for domestic use. If due to the weather conditions the water doesn´t reach its set point temperature, an electrical boiler will assist the heating process. Larger solar installations can also be connected to the central heating of the house or can be used to heat the pool.
Connecting solar panels to the central heating system is especially interesting for people who leave their house unattended for larger periods as it will heat the house during their absence.