Themis (solar power plant)
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The Themis solar power tower was opened by EDF in May 1983 in Targassonne, France (French Cerdagne), not far from the Odeillo solar furnace.
It had a power output of 2 MW. Construction started in 1979 at a cost of 300 millions French francs (about 45 millions euros). It was based on an array of 201 mirrors which heated a boiler (a cavity lined with coolant tubes) at the top of a 100 m tower where the coolant (molten salts) carryied the thermal energy to a vapor generator, itself powering an electric turbine. The molten salts were potassium nitrate (53%), sodium nitrite (40%) and sodium nitrate (7%). The coolant entry temperature was 250 °C and the exit temperature 450 °C. The vapor produced in the vapor generator was at 50 bar and 430 °C.
Themis produced power for three years and then stopped in June 1986, in part due to the difficult management of the coolant.
Themis went into hibernation for more than twenty years, sometimes used as a science facility, an Air Cherenkov Telescope, measuring gamma rays hitting the atmosphere (see IACT).
[edit] Rehabilitation
Recently, a rehabilitation program has been devised due to the high oil prices. The partners are CNRS, the local and regional political authorities of Pyrénées-Orientales and the Tecsol design office.
Currently Themis still has its 201 mirrors (53.70 m² each) on 4 hectares installed on sun following devices called heliostats covering 11 800 m² to send the solar energy towards the hot spot at the top of the 100 m central tower.
The rehabilitation project would repair half of the heliostats in order to develop a power of 1 MW, thanks to a gas turbine installed at the top of the tower, and replace the other half of the mirrors with solar cells.
