Solar power is critical to meeting the world’s need for zero emissions electricity. But solar alone cannot meet the requirements of a 24 hour energy grid. There needs to be some way to store it so it can be put to use after the sun goes down. Researchers in Spain are exploring the possibility of using molten silicon as a storage medium in what is known as a concentrated solar power system or CSP.
Over the years, many systems have been tried for storing electrical power. In Wales, National Grid operates Electric Mountain. It has a lake at the top and another at the bottom. Inside the mountain are enormous conduits that pump water uphill when electrical power is abundant. When a need for extra electricity arises, the water flows back downhill, spinning turbines as it falls.
In the deserts of Nevada, a start-up company wants to build a railway to nowhere. Freight cars loaded with hundreds of tons of concrete blocks would be dragged uphill during the day, only to roll back down again at night, generating electricity as they descend. Also in Nevada, with its open land and abundant sunshine, the Crescent Dunes CSP facility is now online and generating electricity sufficient for about 75,000 homes.
Instead of using solar panels, Crescent Dunes concentrates the sun’s rays to melt salt. The molten salt is than stored in tanks until there is a need for electrical power. It is then used to heat water to make steam to turn conventional turbines. The facility can continue to make electricity for up to 10 hours after the sun sets.
Researchers at the Solar Energy Institute of the Universidad Politécnica de Madrid are working on technology they say that molten silicone is far more efficient than molten salt. It is able to store 1 MWh of energy per cubic meter — 10 times the capacity of molten salt. The researchers say molten silicon is more abundant and less expensive than molten salt. Silicon is the most abundant element in the earth’s crust and melts at about 1,400° C. Salt melts at 801° C and is stored at about 566° C.
Silicone has another important advantage. “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.
There is one more thing to consider. Today, there is a movement toward using lithium ion batteries for grid storage. Lithium is rare and hard to get. Its cost is going up as more batteries are produced. Silicone is plentiful and cheap. Are we seeing the beginning of a system for creating and storing electrical power that will be even less expensive than the amazing low prices set recently on world markets? Perhaps the advent of cheap, abundant, zero emission electrical power is close at hand.
Source: Utility Dive
