The “Solar Pond” technology has made substantial progress in the last few years. Which among the following is / are the use / uses of the Solar Ponds?

Only 1, 2 & 3
Fundamentals of Solar Pond Technology In a clear natural pond about 30% solar radiations reaches a depth of 2 metres. This solar radiation is absorbed at the bottom of the pond. The hotter water at the bottom becomes lighter and hence rises to the surface. Here it loses heat to the ambient air and, hence, a natural pond does not attain temperatures much above the ambient. If some mechanism can be devised to prevent the mixing between the upper and lower layers of a pond, then the temperatures of the lower layers will be higher than of the upper layers. This can be achieved in several ways. The simplest method is to make the lower layer denser than the upper layer by adding salt in the lower layers. The salt used is generally sodium chloride or magnesium chloride because of their low cost. The Solar pond is nothing but a large saline water body in which solar energy is trapped in the salt. The salt solution gets denser with depth, making it possible to maintain a concentrated layer of hot brine at the bottom. Thus a solar pond has layers of varied temperature—the deeper you delve into it, the hotter it gets, seemingly defying a simple heat theory that makes hot- air balloons fly. In India, the TERI had developed a Solar Pond in Bhuj Gujarat to put it to a unique use— supply process heat to an end-user, for the first time in India. The Bhuj solar pond covered an area of 6000 square metres. It was the first-ever solar pond in India to have connected itself to an end-user – supplying industrial process heat to the Kutch Dairy – this pond, covering an area of 6000 square metres, was, at that time, the largest operating solar pond in the world. Applications: •Other than process heating, thermal energy collected in a solar pond can be used in many more applications. •Process heat can produce hot air for industrial and space heating applications. •Solar pond-based desalination system offers cost-effective solution for production of potable water from brackish/sea water. •Using the vapour absorption refrigeration system, the heat contained in a solar pond can be used for cold storage of food products and also for air-conditioning. •The hot brine can also generate electricity, using an organic Rankine cycle engine.