"When electricity is needed, say, after the sun has set, the hot liquid silicon -- so hot that it's glowing white -- is pumped through an array of tubes that emit that light. Specialized solar cells, known as multijunction photovoltaics, then turn that light into electricity, which can be supplied to the town's grid. The now-cooled silicon can be pumped back into the cold tank until the next round of storage -- acting effectively as a large rechargeable battery. "One of the affectionate names people have started calling our concept, is 'sun in a box,' which was coined by my colleague Shannon Yee at Georgia Tech," Henry says. "It's basically an extremely intense light source that's all contained in a box that traps the heat.""