A new liquid silicon based solar battery uses heat to generate light and produce electricity.
The problem with this kind of Thermal Energy Grid Storage Multi Junction Photovoltaic cell is that it has up until now remained too impractical for commercialization. Ordinary molten salt batteries cannot sustain temperatures past 1000 degrees celsius before they start damaging the surrounding infrastructure. The good thing about silicon however is that it can be heated to temperatures that exceed 4000 degrees celsius.
Using that knowledge scientists from MIT have improved upon a previously dormant concept involving the storage of heat generated by concentrated solar power. A new and emerging approach to harvesting solar energy whereby incoming light rays are refocused on to a salt bed by a system of rotating mirrors.
However, this newly resurrected system is more concerned with exploiting the irradiation of light that occurs when liquid silicon is heated to a sufficiently high temperature. In the spirit of concentrated solar power – a series of mirrors refocus incoming light rays on to a silicon tubing system until the element assumes a white-hot molten state where it then begins to emit light that can be harvested by solar panels in a secondary storage tank
Scientists also take advantage of any excess heat to boil a separate tank of water, producing steam, and along with it – more electricity.
After all of that’s accounted for the left over silicon is subsequently pumped back in to the first graphite tank for recycling. The first preliminary tank is held at a constant temperature of 3450 degrees while the secondary harvester is stored at a higher temperature of 4350 degrees.
“The reason that technology is interesting is, once you do this process of focusing the light to get heat, you can store heat much more cheaply than you can store electricity,” says Asegun Henry, lead researcher on the study.
Both graphite tanks measure a significant 33 ft (10 m) wide and scientists claim that one device would be enough to power 100 000 homes.
“This technology has been around for a while, but the thinking has been that its cost will never get low enough to compete with natural gas.
According to researchers the technique flexible, as it can be implemented almost anywhere, and is much less expensive than contemporary methods – about half the price of hydroelectric energy.
“This is geographically unlimited, and is cheaper than pumped hydro, which is very exciting,” says Henry.
“In theory, this is the linchpin to enabling renewable energy to power the entire grid.”
Published in the journal Energy & Environmental Science.
Concentrated photovoltaic solar power recently broke through 40% energy conversion efficiency. Almost twice that of commercialized silicon cells.