Concentrating solar power plant. Heliostat array and central tower of the Gemasolar concentrating solar power plant in Seville, Spain. Concentrating solar power plants use arrays of heliostats (mirrors with sun-tracking motion) to reflect sunlight and concentrate it onto a receiver (bright, top) at the top of a central tower. The concentrated solar energy is then used to produce electrical power by boiling water to produce steam, which is piped to a steam turbine electricity generator. This power plant uses molten salt as its heat transfer fluid and energy storage medium.