Molten Salt Thermal Storage

Molten salt thermal storage holds heat by keeping a mixture of salts, typically sodium and potassium nitrate, liquid at high temperature in insulated tanks, then drawing that heat back out later to raise steam and run a turbine. It is used mainly alongside concentrated solar power plants, where mirrors heat the salt during the day so the plant can keep generating electricity after sunset, and it is also studied as a way to store surplus heat from other sources. The salt mixture stays liquid over a wide temperature range and can hold heat for many hours with modest losses, which is what makes it useful for shifting solar generation into the evening.