Molten Salt Transfers, Stores Heat in Italian CSP Plant
July 30, 2010
A 5-megawatt concentrating solar power (CSP) plant, owned by Italian power company Enel, is the first parabolic trough solar field in the world to use molten salts as both the heat transfer and storage fluid. The facility is also the first to integrate a combined-cycle gas plant and a solar thermal power plant for electricity generation. The Archimede solar thermal power plant in Priolo Gargallo in Syracuse, Sicily, was inaugurated July 14.
The plant uses about 30,000 square meters of mirrors on the parabolic trough collectors to concentrate sunlight onto 5,400 meters of pipe carrying the molten salt fluid. In this way, the fluid is heated to about 550°C, then stored in a high temperature tank before being used to power a steam generator. The high-temperature steam and pressure supplements the turbine in the adjacent combined-cycle power plant to generate electricity when needed, reducing consumption of fossil fuels.
The molten salt used in the system is a eutectic mixture of sodium nitrate and potassium nitrate, which can store heat for prolonged periods. Enel predicts that using the molten salt system will save 2,100 tonnes of oil equivalent, reducing carbon dioxide emissions by about 3,250 tonnes. (One tonne equals 1,000 kilograms or 2,204.6 pounds.)
Archimede gets its name from the famous mathematician and physicist, Archimedes; legend says he used mirrors to set fire to Roman ships besieging Syracuse during the Punic War of 212 BC.