Breakthrough in solar energy: ten times more effective solar power may be available in three years

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Breakthrough in solar energy: ten times more effective solar power may be available in three years
Jeremy Hance, mongabay.com
July 10, 2008

The breakthrough scientists have been waiting for to make solar power cheaper, more efficient--and therefore a more effective replacement for traditional energy sources--has been made by a group of MIT researchers.

The researchers have updated a relic power source developed in the 1970s called luminescent solar concentrator or LSC. An LSC collects light through dyes painted on a transparent surface; the light is then transported across the surface to solar cells at the edge. In the past LSCs have been used with transparent plastic sheets, but MIT's solar concentrator employs glass instead.

LSCs never took off in the 70s because much of the light was lost when transferred from the dyes to the solar panels at the concentrator's edge. The team at MIT used current optical techniques for lasers to get around the problem. The dyes are now applied only to the surface of the glass and in very specific ratios providing more control over the sun's rays.

An artist's representation shows how a cost effective solar concentrator could help make existing solar panels more efficient. The dye-based organic solar concentrator functions without the use of tracking or cooling systems, greatly reducing the overall cost compared to other concentrator technologies. Dye molecules coated on glass absorb sunlight, and re-emit it at a different wavelengths. The light is trapped and transported within the glass until it is captured by solar cells at the edge. Some light passes through the concentrator and can be absorbed by lower voltage solar cells underneath. Alternatively, the partially transmissive concentrator can function as a window. Graphic not to scale. Image courtesy / NSF

Organic solar concentrators collect and focus different colors of sunlight. Solar cells can be attached to the edges of the plates. By collecting light over their full surface and concentrating it at their edges, these devices reduce the required area of solar cells and consequently, the cost of solar power. Stacking multiple concentrators allows the optimization of solar cells at each wavelength, increasing the overall power output. Photo / Donna Coveney

"We made it so the light can travel a much longer distance," Jon Mapel, one of the researchers, said. "We were able to substantially reduce light transport losses, resulting in a tenfold increase in the amount of power converted by the solar cells." This increase in efficiency by ten times could result in a true renewable energy revolution.

Current systems of solar power "track the sun to generate high optical intensities, often by using large mobile mirrors that are expensive to deploy and maintain," the engineers explain in the journal Science. But LSCs will be cheaper because the expensive solar cells will only be on the edges of the flat surface, instead of covering the full area.

These new LSCs would be so simple to construct that the researchers believe they could be available in just three years. The technology could also be added to already-existing solar panels, increasing their efficiency by 50 percent. Three of the researchers have started a new company, Covalent Solar, to manufacture and sell the new technology.

"This accomplishment demonstrates the critical importance of innovative basic research in bringing about revolutionary advances in solar energy utilization in a cost-effective manner." Dr. Aravinda Kini said. A sponsor of the MIT team's work, Kini is program manager in the Office of Basic Energy Sciences in the U.S. Department of Energy.

With the increasing cost of oil and gas worldwide and their large role in global climate change, the timing of this new solar technology could not be more auspicious.

Michael J. Currie, Jonathan K. Mapel, Timothy D. Heidel, Shalom Goffri, Marc Baldo. High-Efficiency Organic Solar Concentrators for Photovoltaics. Science 10 July 2008.

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