Researchers at the Solar Energy Institute of the Universidad Politécnica de Madrid are working on an energy storage system that uses molten silicon that could be used in some solar power plants or with a thermovoltaic panels.
The researchers say molten silicon is more abundant, less expensive and a more efficient storage medium than molten salt, which is already in use at some concentrating solar power plants.
The researchers have begun to manufacture their first lab-scale prototype and have also started SILSTORE, a business project that aims to commercialize their results.
Molten salt is used at the Crescent Dunes concentrated solar power plant near Tonopah, Nev., which went online last year.
The plant, under a 25-year power purchase agreement with NV Energy, uses concentrating solar panels to heat salt to a molten state. The molten salt stores energy and the heat can be used to run a conventional generator after the sun goes down.
Universidad Politécnica de Madrid (UPM) are now exploring the use of molten silicon to store energy. Silicon, which is the most abundant element in the earth’s crust, is molten at about 1,400° C. Salt melts at 801° C and is stored at about 566° C.
The UPM researchers say molten silicon can store more than 1 MWh per cubic meter, 10 times more than salts can. In addition, “at such high temperatures, silicon intensely shines in the same way that the sun does, thus photovoltaic cells, thermophotovoltaic cells in this case, can be used to convert this incandescent radiation into electricity,” Alejandro Datas, a researcher on the project told Science Daily.
Thermophotovoltaic cells can produce 100 times more electric power per unit area than conventional solar cells and have higher conversion efficiencies, even over 50%. The researchers say that can result in a compact system with no moving parts that can operate silently and uses inexpensive materials.
Correction: An earlier version of this post misidentified the CSP plant that uses molten salt as a storage medium. It is the Crescent Dunes CSP plant, not the Ivanpah plant.