A small artificial lake used to collect solar energy, which can then be removed from the pond in the form of useful heat, or an external heat exchanger, or a heat exchanger placed on the bottom of the pond, which converts the thermal energy into electricity.

A solar pond that consists of three main layers; the top one is near ambient temperature and has low salt content, while the bottom one is very hot and salty and is lined with a dark-colored material.

The middle (gradient) zone acts as a transparent insulator, permitting sunlight to be trapped in the bottom layer (from which useful heat is withdrawn).

This middle layer, which increases in brine density with depth, counteracts the tendency of the warmer water below to rise to the surface and lose heat in the air.