The new design stores heat generated by excess electricity from solar or wind power in large tanks of white-hot molten silicon, and then converts the light from the glowing metal back into electricity when it’s needed. The researchers estimate that such a system would be much more affordable than lithium-ion batteries, which have been proposed as a viable, though expensive, method to store renewable energy. They also estimate that the system would cost about half as much as pumped hydroelectric storage—the cheapest form of grid-scale energy storage so far.
Delivering solar- or wind-generated power on demand, the system, which uses molten silicon, should be cheaper than other leading options.
Source : https://lifeboat.com/blog/2019/02/sun-in-a-box-a-new-way-to-store-renewable-energy-for-the-grid