School of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran.
Renewable energy is a promising alternative to fossil fuel-based energy and is on the rise, largely to reduce dependency on limited reserves of fossil fuels and to mitigate impacts of climate change. Solar energy is an important source of renewable energy. The development of affordable, inexhaustible and clean solar energy technologies will have huge longer-term benefits. Among such technologies, solar ponds are considered as reliable and economical means of solar energy application. A solar pond is a body of water which collects solar radiation and stores it as thermal energy for a long period of time in the form of a simple and low cost solar energy system. Salt gradient solar pond, capable of providing a considerable quantity of hot water, is one of the most efficient and practical types of solar ponds. These ponds have received wide currency in both research and industrial fields. Heat absorbed in the salt gradient solar pond can be extracted in different ways for various thermal applications, ranging from domestic to industrial uses. The present article introduces solar ponds theory and applications with emphasis on salt gradient solar ponds including mathematical models describing their behavior.