Solar pond

Solar thermal energy

A solar pond is a pool of saltwater which collects and stores solar thermal energy. The saltwater naturally forms a vertical salinity gradient also known as a "halocline", in which low-salinity water floats on top of high-salinity water. The layers of salt solutions increase in concentration with depth. Below a certain depth, the solution has a uniformly high salt concentration.

This keyword could refer to multiple things. Here are some suggestions: