Solar Pond

A solar pond is a pool of saltwater that collects and stores solar thermal energy. The saltwater naturally forms a vertical salinity gradient, known as a halocline, in which low-salinity water floats on top of high-salinity water and the layers of salt solution increase in concentration, and therefore density, with depth, so that below a certain depth the solution reaches a uniformly high salt concentration. These density differences between the layers prevent the convective mixing that would otherwise dissipate heat, allowing the bottom layers of a solar pond to reach temperatures around 90 degrees Celsius while the upper layers remain at around 30 degrees Celsius.