WASHINGTON, US - USING sheets of glass covered with organic dyes, scientists have devised an efficient and practical solar power device that they believe can help make this clean, renewable energy source more affordable.

Experts eager for energy sources that do not involve the burning of fossil fuels often point to the promise of solar energy - harnessing sunlight to make electricity. But solar power so far has proven costlier than standard energy sources.

Writing on Thursday in the journal Science, Massachusetts Institute of Technology researchers describe the development of a new type of 'solar concentrator' that may provide a better way to extract energy from the sun.

At the edges of the glass are located small solar cells that then transform the light into electricity.

'It consists of just a piece of glass with a layer of paint on top of it,' MIT electrical engineering professor Marc Baldo, who led the research, said in a telephone interview.

'The idea is the light comes in and hits the paint. The paint then bounces the light out to the edges of the glass. All you need is the solar cells on the edges. So we think we can use this to reduce the cost of solar electricity,' added said.

MIT researcher Jonathan Mapel, who also worked on the study, said the hope is that the use of this sort of technology can help bring the cost of solar power closer to the cost of conventional fossil fuel power sources such as coal.

'One of the challenges with solar (energy) in general is that it's just too high in cost. And what you'd like to do is reduce the price of solar electricity,' Mr Mapel said.

Solar concentrators collect sunlight over a large area - in this case the panes of glass - and concentrate it into a small solar cell that turns the light into electricity.

Existing solar concentrators use mirrors or lenses to concentrate the light. The sheets used in this research are flat and light, thus can be utilised in solar panels placed on roofs or even used as windows that could generate power.

The new system, unlike some concentrators, does not have to move to track the progression of the sun across the sky in order to provide a continuous power source, Prof Baldo said.

The researchers think their system could be available within three years and even could be added onto existing solar-panel systems to increase their efficiency.

'This accomplishment demonstrates the critical importance of innovative basic research in bringing about revolutionary advances in solar energy utilisation in a cost-effective manner,' Mr Aravinda Kini of the United States Department of Energy's Office of Science, a sponsor of the work, said in a statement.

Some of the MIT researchers are forming a company, Covalent Solar, based in Boston to develop and market the technology. -- REUTERS