While the Peraringnar Anna Technological University in Madras, in its quest for alternative sources of energy, has come out with Asia's first 'ethanol car', the Tamil Nadu Electricity Board (Tneb) has formulated proposals for another first in India - generation of thermal power from the sea. The proposal envisages technical collaboration with the General Electric Company, and the Union Government has given the board the "go ahead" for talks with the American firm to finalise the details and prepare a project report.
The plan is to have a 25 MW pilot plant near Kulasekharapattinam, a small port in Tirunelveli district, with provisions for further expansion. The scheme is different from tidal power generation which some European countries are reportedly attempting. The tidal power principle is in action, though on a smaller scale, in Madras harbour where wave-activated generators light the buoys.
A. Chockalingam, 53, who was until recently chairman of Tneb, believes that "using this idea for large-scale power generation in India may not be practicable because it requires huge waves, and the sea around is generally placid."
The Principle: The Tneb scheme will utilise the temperature difference between the warm surface water and the cold deep water of the sea. This temperature difference, which in tropical regions is as high as 20 degrees centigrade, is caused by solar radiation of the earth, 70 per cent of which falls on the sea. The sea not only collects it, but stores it. The temperature difference always exists because of the operation of currents and cross-currents, during day and night, and in sunny and cloudy weather. Thus, the need to store energy when there is no sunshine - a process which makes land-based solar power plants very costly - is obviated.
A heat exchanger will help transform this energy into electricity. The warm surface sea water (27 degrees centigrade) is led into a boiler where it gasifies a liquid heat medium like ammonia or freon both of which boil at less than 25 degrees centigrade. This gas will drive a turbine - land-based or sea-based-to generate electricity. The same gas is later cooled and liquified by cold water (seven degrees centigrade) pumped up from the deep, and is recycled into the boiler to repeat the process.
Feasible: The process is simple, and the power to be had unlimited. But it needed an energy crisis to goad American scientists into action and discover that the idea was a feasible one. They have estimated that the entire power requirement of the US 20 years from now could be met by harnessing a mere 0.004 per cent of the solar energy stored by the sea near the equator. Their estimate of the power potential of the surface waters of the Bay of Bengal between Madras and Cape Comorin is a phenomenal 10,000 MW, almost four times Tamil Nadu's present installed hydel and thermal generating capacity.
The Tneb has selected Kulasekharapattinam for the pilot plant because data collected by the board has revealed that the temperature of the surface waters here does not go below 26 degrees centigrade. The cost of the project, according to Chockalingam, might be a little more than a coal-based thermal plant's of a similar size. The capital outlay would be greater because the heat exchangers would have to process 10 times the water required by a coal-based plant to generate the same amount of heat. This would require a larger exchange surface. Being primarily a submarine project, use of costly non-corrosive metal would also be essential.
American scientists believe that if the heat transfer rate could be increased-if the ammonia or freon could be boiled with a lesser quantity of water-the size of the exchangers, and thereby the cost, could be drastically reduced. Research is on to quicken the boiling of ammonia. One method being considered is the coating of the surface of the exchangers with high heat conductors like aluminium.
Plus Points: But Chockalingam believes that even as the scheme stands now, there are advantages which no other plant- hydel, thermal or atomic-has. Says he: "For one, the cost of input is practically nil. The availability of this input-solar energy- is perennial and abundant. There is no pollution hazard. At the same time there can be an additional bonus which might prove a windfall for fishermen: it has been found that the fish population in the area covered by the plant multiplies rapidly, feeding on the fauna and flora pumped up along with the water from below."
The answer to the seemingly insurmountable energy problem may after all lie not below the sands of Arabia but in the depths of the ocean.