One of the obstacles to the success of renewable technologies is to discover a cheap and useful storage system. For solar thermal power plants different options have been investigated and one of them is that of molten salts. However, 2 fires in three months in Abengoa’s La Solana plant in Arizona (USA) have triggered doubts about their operation.
Abengoa’s jewel in the crown is its stellar solar thermal plant of La Solana, representing the company’s ability to develop and implement this technology and being the most powerful of all its facilities with 280 MW. However, the plant has had two fires in just 3 months, both times caused by excessive temperature of molten salts, the energy storage system used in this facility, which in principle should allow the plant to produce up to six hours without sunlight.
Molten salt at high temperature
Solar thermal power plants with molten salt heat energy in the central receiver and store it until the supply company needs electricity. At that time, the molten salt flow into a steam generator driving a standard steam turbine to produce reliable and continuous electricity during peak hours.
The use of this type of solid materials for thermal energy storage seems a logical choice for its low price, modularity, scalability and relative simplicity. But some experts doubt the functionality of this solution considering it limited due to thermal instability.
A breakthrough in solar thermal energy can be in overcoming the limits of the temperatures generated by solar thermal capture devices and enable heat storage cheap enough to operate solar plants with maximum performance throughout the day.
La Solana features
Solana is located about 100 km southwest of Phoenix, near Gila Bend, Arizona. The project began to take shape with the signing of a power supply- purchase agreement with Arizona Public Service (APS), the state’s largest utility. The latter acquired 100% of the electricity that Solana will produce in the next 30 years. Construction began in late 2010.
Solana is the world’s largest parabolic trough plant with an installed capacity of 280 MW (gross) and a six hours thermal energy storage system, allowing meet peak demand in the region at night, especially in summer. Its solar field spans 777 ha, with approximately 3,200 parabolic trough collectors.
The mirrors concentrate sunlight on a receiver tube inside which circulates a fluid that absorbs heat reaching high temperatures. Then this fluid transforms water into steam, to then go to a turbine and finally generate electricity.
Abengoa successfully operated a molten salt based heating storage demonstration plant in Spain, but, it seems, with Abengoa having declined to make any statement to EnergyNews, this is what is now failing in this system which should provide six hours of thermal storage at maximum capacity.