Power tower of the Themis solar power plant near Targasonne, Pyrenees-Orientales, France. Themis was an early experimental solar thermal power plant that operated between 1983 and 1986. Sunlight reflected from heliostats (large mirrors facing the sun) on the surrounding ground heated a solar boiler containing a coolant (salts of potassium and sodium) at the top of the tower. The heated molten salts transferred heat to a steam generator powering a turbine which produced electricity. After a period of closure the site is now used for several solar research and development projects.