“Water, water, every where, Nor any drop to drink , ” cries out the sailor in Samuel Taylor Coleridge’s classic ‘The Rime of the Ancient Mariner.’
The desperation is not entirely unknown in Peninsular India, where, even with seas surrounding the land on three sides, water often eludes parched tongues.
With desalination — that involves converting saline sea water to potable water — being out of reach currently for the shallow pockets of the government, researchers of Indian Institute of Science (IISc) have hit upon the idea of utilising copious solar energy in the South to reduce the costs of the process.
Ravinder Kumar and Umanand L., from the Department of Electronic Systems Engineering at IISc, have developed a solar hybrid desalination system that works for saline and brackish water. The process described in the International Journal of Low Carbon Technologies shows that at its peak (around 27 degree C) could the system can purify nearly 6.5 litres of saline water per sq.m. of the instrument in six hours of use (tested between 9 a.m. and 3 p.m.).
The stepped solar-still, comprising of semi-circular pipe sections welded progressively one next to the other so as to maintain a constant slope was fabricated to serve as the water channel basin. Vacuum jackets were provided to minimize thermal losses. The instrument could hold between 3 and 4 litres for treatment. During the experimentation, solar intensity was observed at 718.76 Watt per sq.m. With the set-up ensuring pressure was high within, saline water saw evaporation at temperatures lesser than 100 degree C. Water was further pumped in and out using photovoltaic cells as a source of energy — making the instrument self-reliant.
Mr. Kumar believed the system met the major objectives of desalination system: to reduce life span cost, while meeting performance requirements. “This system shows promise that the problem of clean drinking water can be solved in any coastal area where seawater and sunlight are available freely,” he said.