The first power plant in the world to use molten salt technology as a heat transfer fluid has been inaugurated in Italy by Enel.
The Archimede power plant, located at Priolo Gargallo in Sicily, is also the first plant in the world to integrate a combined cycle gas facility with a solar thermal plant, says the Italian utility.
The version of molten salt technology used in this 5 MW plant was developed by Enea and allows energy captured from the sun to be stored and used to generate electricity at night or in overcast conditions. Annually the plant will avoid the use of 2100 tonnes of oil equivalent of fuel and the emission of about 3250 tonnes of carbon dioxide.
The solar thermal plant consists of a field of about 30 000 m2 of parabolic mirrors that concentrate sunlight onto 5400 m of piping carrying the molten salts. The molten salts used in the system are a mixture of sodium nitrates and potassium, which can accumulate heat for prolonged periods.
The thermal energy harvested by the system produces high pressure steam that is channelled into the steam turbines of the combined cycle power plant to produce electricity. The solar collectors (i.e., the parabolic mirrors and pipes or receivers), together with a steam generator and two heat storage tanks – one cold and one hot – make up the solar portion of the system.
When the sun shines, the thermal fluid drawn from the cold tank is circulated through the network of parabolic collectors, where it is heated to a temperature of 550°C and injected into the hot tank, where the thermal energy is stored. The fluid is then drawn from the hot reservoir to produce steam at high pressure and temperature, which is sent to Enel’s nearby combined cycle plant.
This system enables the plant to generate electricity at any time of the day and in all weather conditions until the stored energy is depleted.
The plant is called “Archimede” because the rows of huge parabolic mirrors used to capture the sun’s rays rsemble, says Enel, the “burning mirrors” that Archimedes is said to have used to set fire to the Roman ships besieging Syracuse during the kingdom’s war with the Romans, 214-212 BC.
