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Stretched solar lens cuts space costs

21 Aug 2003

An ultra-light Fresnel lens harnesses sunlight with record efficiency, reducing the weight and cost of solar panels launched into space.

Researchers in the US have developed a type of lens that promises to dramatically reduce the weight and cost of solar panels used to generate power in space.

The new lens design from Mark O’Neill and colleagues at Entech converts sunlight to electricity while cutting the amount of solar cell material needed per unit of power generated by 85%. The result is a design that produces a record-breaking 180 W per kilogram of solar cell.

The key to the efficient light collection is an ultra-light stretched Fresnel lens. Made from flexible silicone rubber, the lens is just 140 µm thick. O’Neill told Optics.org that the design provides outstanding optical efficiency, and exceptionally high tolerance of errors in the lens shape. It also features a prism covering the solar cell to ensure that there is no loss of conversion efficiency caused by imaging shadows onto the cell.

As a result, the overall solar-to-electric conversion efficiency is 30% - the best yet achieved. “Our 30% module efficiency results from a cell solar-to-electric efficiency of 33% and a lens optical efficiency of 92%,” said O’Neill.

He added that new solar cell technology – so-called multi-junction cells that use a combination of semiconductor materials to convert a greater portion of solar light into electricity than conventional silicon solar cells – is compatible with the Fresnel concentrator. A triple-junction cell, made from gallium indium phosphide, gallium arsenide and germanium, converts light over the 0.36-1.8 µm wavelength range.

“We are redesigning our lenses for higher concentration ratios, to minimize the size and cost of the new solar cells. Our next-generation terrestrial systems will be approximately twice as efficient as the current state-of-the-art in terrestrial technology – a major leap forward.”

Author
Michael Hatcher is technology editor of Opto & Laser Europe magazine.

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