A solar pond is a large scale solar thermal collector with an integrated arrangement for storage of heated water.
A solar pond is simply a pool of saltwater which collects 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 in concentration (and therefore density) with depth. Below a certain depth, the solution has a uniformly high salt concentration.
When the sun’s rays contact the bottom of a shallow pool, they heat the water adjacent to the bottom. When water is at the bottom of the pool, it becomes less dense, and convection begins. Solar ponds heat water by impeding this convection. Salt is added to the water until the lower layers of water become completely saturated . High-salinity water is a low-salinity water-soluble, high-temperature water-soluble solution. . This greatly reduces heat loss, and allows for high-salinity water to get up to 90 ° C while maintaining 30 ° C low-salinity water. This hot, hot water can be used for electricity generation, through a turbine or a source of thermal energy.
Advantages and disadvantages
- The approach is, particularly, attractive for rural areas in developing countries . Very large area collectors can be set up for the cost of the clay or plastic pond liner.
- The accumulating salt crystals have been removed and can be used.
- No need for a separate collector.
- The extremely-large thermal mass power is generated night and day.
- Relatively low-temperature operation means solar energy conversion is typically less than 2%. 
- Due to evaporation, non-saline water is constantly required to maintain salinity gradients.
The energy obtained is in the form of low-grade heat of 70 to 80 ° C compared to an assumed 20 ° C ambient temperature. According to the second law of thermodynamics (see Carnot-cycle ), the maximum theoretical efficiency of a cycle that uses a high temperature reservoir at 80 ° C and has a lower temperature of 20 ° C is 1- (273 + 20) / (273 + 80) = 17%. By comparison, a power plant’s heat engine with high-grade heat at 800 ° C would have a maximum theoretical limit of 73% for converting heat into useful heat (and thus would be forced to divest as little as 27% in waste heatto the cold temperature reservoir at 20 ° C). The low efficiency of solar ponds is usually Justified with the argument que la ‘collector’ being white just a plastic-lined pond, Potentially might result in a wide-scale system of lower overall That Is levelised energy cost than a solar concentrating system .
Further research is aimed at addressing the problems, such as the development of membrane ponds. These use a thin permeable membrane to separate the layers without allowing salt to pass through.
The Largest operating solar pond for electricity generation Was the Beit Haarava pond built in Israel and up to 1988. It operated up Review: had an area of 210,000 m² and gave an electrical output of 5 MW. 
India has been established in Bhuj , in Gujarat. The project was sanctioned under the National Solar Pond Program by the Ministry of Non-Conventional Energy Sources in 1987 and completed in 1993 after a collaborative collaborative effort by TERI, the Gujarat Energy Development Agency, and the GDDC (Gujarat Dairy Development Corporation Ltd.). The solar pond has been proven to supply 80,000 liters of hot water daily to the plant.It is designed to supply about 22,000,000 kWh [ citation needed ] of Thermal Energy annually. The Energy and Resources InstituteProvided all technical inputs and completed the complete execution of research, development, and demonstration. TERI operated and maintained this facility until 1996 before handing it over to the GDDC. The solar pond functioned effortlessly until the year 2000 when severe financial losses crippled GDDC. Subsequently, the Bhuj earthquake left the Kutch Dairy non-functional. 
The 0.8-acre (3,200 m 2 ) solar pond powering 20% of Bruce Foods Corporation’s operations in El Paso, Texas is the second largest in the US It is also the first ever salt-gradient solar pond in the US 
- Ocean thermal energy conversion
- Ice pond
- Seasonal thermal energy storage (STES)
- Thermal storage
- Deep lake water cooling
- Cooling pond
- Salt evaporation pond
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