Says Amit Kumar, one of the TERI scientists behind the technology: ``We had a lot of meetings with the Gujarat government and business houses, but for the want of financial support and a policy to encourage this technology, nothing has moved.''

Solar ponds are essentially low-cost solar collectors with integrated storage and can deliver industrial process heat to marine chemical industries, process industries and dairies. Alternately, these solar ponds can be used to desalinate water in highly saline areas and provide drinking water to the people living in these areas.

The Bhuj solar pond was conceived as a research and development project of TERI, which took over nine years to establish, to demonstrate the feasibility of using a salt gradient pond for industrial heating. The plant was a collaborative effort between the Gujarat Energy Development Agency (GEDA), the Gujarat Dairy Development Corporation Limited (GDDCL), and TERI.

The pond had a design capacity of supplying 80,000 litres of hot water per day to the dairy at 70 deg C and the target was achieved, says Kumar. ``The pond supplied over 20 million litres of hot water to the dairy between September 1993 and March 1997,'' says Kumar. But then GDDCL's plant in Kutch fell into financial trouble three years ago and the pond fell into disuse along with the closure of the dairy.

The Bhuj solar pond was the fist large-scale solar pond in an industrial environment to cater to the actual user demand. ``The successful demonstration of the solar pond to supply heating for the dairy was accomplished. However, this technology will be throttled in its infancy unless the government does something about it,'' says Kumar.

The solar pond was constructed using a cost-effective and completely indigenous lining developed with a combination of locally mined clay and plastic. The unit cost of construction on the 6,000 sq mt pond was 415 per sq mt (around Rs 500 at 1997 prices) compared with $30 per sq mt of a similar pond constructed in Beth ha Arava in Israel in 1984. The total cost of construction was Rs 87 lakh but the savings to the dairy were to the tune of 935 mt of lignite per year at full capacity utilisation. ``The payback period worked to be less than five years without any subsidy or tax incentives,'' says Kumar.

Solar ponds can be effectively used as replacements in industries that use fossil fuel to generate thermal energy especially in the marine chemicals sector or industries located in areas which have saline water. Solar ponds can be used for process heating, refrigeration, water desalination, production of magnesium chloride, bromine recovery from bittern, enhancement of salt yield in salt farms, etc. The techno-economic viability of the solar pond has been proved, but it only needs to be adopted.