It’s the thing that seems to bother most people whenever solar power is discussed: “What happens at night?” The most sophisticated solar plants have found ways to compensate for the lack of sunlight during the night by coupling solar plants with other energy sources or by storing some energy during the day to be used at night. But now a new power plant developed by Torresol Energy in Spain has claimed to offer once and for all a reliable 24-hour solution to solar energy.


The Gemasolar plant (above) uses hudreds of mirrors to reflect concentrated sunlight toward a central tower, where water is heated to steam, which drives a turbine that produces electricity. This scheme is becoming increasingly more popular than the traditional photovoltaic (PV) cell systems because of lower costs and comparable efficiency. The CSP systems also have the advantage of being easily integrated into existing power plants that already use turbines.


During the day, energy is stored by heating up large tanks of molten salt composed of a mixture of 60 percent potassium nitrate and 40 percent sodium nitrate. The molten salt is able to retain a very large amount of heat — enough to drive the plant for 15 hours without sunlight. Although molten salt has been used in other plants to store heat energy, the efficiency achieved by Torresol is new.

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The plant has a production capacity of 19.9 Megawatts and although this is relatively small as far as power plants go, the fact that the plant runs continuously means that the effective production is comparable to a traditional 50 Megawatt solar power plant. 

Credit: Torresol Energy