Lithium-ion batteries are the ones consumers are most familiar with, so it seems like the obvious choice to scale them up for grid-scale energy storage – as Tesla did with the world’s biggest battery in Australia. But since lithium is relatively hard to come by, it may not be the best choice. Researchers at MIT have outlined a new design they call a “sun in a box,” which stores energy as heat in molten silicon and harvests it by tapping into the bright light it emits.
The new system, which the team calls Thermal Energy Grid Storage-Multi-Junction Photovoltaics (TEGS-MPV), is based on the molten salt batteriesthat sit at the heart of grid-scale energy storage systems like concentrated solar. But there are a few problems with salt as a storage medium – for one, it becomes quite corrosive when the heat is cranked up.
“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. “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. So there was a push to operate at much higher temperatures, so you could use a more efficient heat engine and get the cost down.”