Trapping solar energy in space

Can solar power ever become a major source of energy?

Published: Saturday 15 November 1997

scientists feel that it is possible to trap solar power in outer space, beam it to the Earth, and convert it into electricity. With the help of latest techniques, they hope that solar energy could be delivered at prices equal to or even lower than ground-based alternatives without big environmental drawbacks. The National Aeronautics and Space Administration (nasa) has recently studied nearly 30 solar power satellite (sps) concepts.

Researchers at the nasa are probing a method of launching 50 sq km solar panels orbiting in space to gather the Sun's rays and beam them to the Earth in forms of microwaves. The rays would then be gathered by 70 sq km receivers and converted into electricity. John Mankins, who led the nasa's recent Solar Power Satellite (sps) research, says that scientists have been able to design more efficient and lighter solar panels. So, there is no need of sending astronauts in space to fix the components. The advanced computing system helps each piece of a satellite to assemble itself.

However, Lucien Deschamps, adviser at the study and research division of Electricite de France, says that one of the biggest problems with sps is the cost of space transportation. At present, the transportation cost for sps is nearly us $10,000 per kg of payload, which makes it extremely expensive to launch solar panels weighing 35-50 tonnes. Unless the transportation cost is reduced a hundredfold, the project may not be feasible.

Harry Ruppe, director emeritus of space technology at the Technical University of Munich, says that the biggest problem is not the transportation of the sps, but the conservation of solar energy involved in beaming the Sun's power to the Earth. The process includes conversions from solar energy to electric energy, from electric energy to microwaves and from microwaves back into electric energy. According to him, the method is only 30 per cent efficient. So, if the proposed goals are to be achieved, investments must be made to increase the efficiency of all the technologies involved in sps, he says.

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