Using silicon in tanks to store renewable energy

Silicon tanks for renewable energy storage

Concentrated Solar Power, which uses heat from the sun to run turbines to create electricity, has long stored excess heat in molten salt to power turbines at night. MIT researchers have used that idea as a concept for a new way to store heat that is cheaper than any other grid-scale energy storage and it can use any form of renewable energy, not just CSP. This could be a seriously big deal.

This new system stores excess heat in tanks of silicon, which can withstand heat up to 4,000 degrees, much hotter than the 1,000 degree limit for molten salt. More heat means more power for creating electricity. And it can use excess energy from solar PV or wind to heat the silicon. It is cheaper than pumped hydro, which currently is the least expensive way to store grid-scale energy. (Batteries are way more expensive.)

The system would consist of a large, heavily insulated, 10-meter-wide tank made from graphite and filled with liquid silicon, kept at a “cold” temperature of almost 3,500 degrees Fahrenheit. A bank of tubes, exposed to heating elements, then connects this cold tank to a second, “hot” tank. When electricity from the town’s solar cells comes into the system, this energy is converted to heat in the heating elements. Meanwhile, liquid silicon is pumped out of the cold tank and further heats up as it passes through the bank of tubes exposed to the heating elements, and into the hot tank, where the thermal energy is now stored at a much higher temperature of about 4,300 F.

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.

The system would consist of a large, heavily insulated, 10-meter-wide tank made from graphite and filled with liquid silicon, kept at a “cold” temperature of almost 3,500 degrees Fahrenheit. A bank of tubes, exposed to heating elements, then connects this cold tank to a second, “hot” tank. When electricity from the town’s solar cells comes into the system, this energy is converted to heat in the heating elements. Meanwhile, liquid silicon is pumped out of the cold tank and further heats up as it passes through the bank of tubes exposed to the heating elements, and into the hot tank, where the thermal energy is now stored at a much higher temperature of about 4,300 F.
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.