Thermal Energy Storage

Thermal energy storage is the practice of capturing heat or cold for later use, holding it anywhere from a few hours to an entire season, through one of three mechanisms: sensible heat, which simply raises the temperature of a storage material such as water, molten salt or rock; latent heat, which stores energy in a material change of phase, such as melting ice; and thermochemical storage, which uses a reversible chemical reaction. The Solana Generating Station in Arizona stores six hours of its generating capacity in molten salt, letting it keep supplying power after the sun sets, and Spain Gemasolar plant used its own molten salt storage to generate electricity around the clock for 36 consecutive days in 2013. At the seasonal scale, the Drake Landing Solar Community in Alberta, Canada stores summer solar heat underground and meets 97 percent of its winter heating needs from it, and a Finnish facility at Mustikkamaa operates an 11.6 gigawatt hour underground water storage system. Thermal storage is considered an increasingly important tool for balancing electrical grids that draw a growing share of their power from variable solar and wind generation.