Solar power tower

Concentrating solar power towers:

• Top: Solar towers of the Ivanpah facility, the world's largest solar thermal power station in the Mojave Desert, southeastern California
• Middle: PS10, the world's first commercial solar power tower in Andalusia, Spain (left) and Ashalim Power Station in Negev, Israel (right)
• Bottom: The THEMIS solar power tower in the Eastern Pyrenees, France (left) and the German experimental Jülich tower (right)

A solar power tower, also known as 'central tower' power plant or 'heliostat' power plant, is a type of solar furnace using a tower to receive focused sunlight. It uses an array of flat, movable mirrors (called heliostats) to focus the sun's rays upon a collector tower (the target). Concentrating Solar Power (CSP) systems are seen as one viable solution for renewable, pollution-free energy.^[1]

Early designs used these focused rays to heat water and used the resulting steam to power a turbine. Newer designs using liquid sodium have been demonstrated, and systems using molten salts (40% potassium nitrate, 60% sodium nitrate) as the working fluids are now in operation. These working fluids have high heat capacity, which can be used to store the energy before using it to boil water to drive turbines. Storing the heat energy for later recovery allows power to be generated continuously, while the sun is shining, and for several hours after the sun has set (or been clouded over).