Hike in Solar Concentrator Efficiency

Monday, January 23, 2012 @ 05:01 PM gHale

Redesigned luminescent solar concentrators can now be more efficient at sending sunlight to solar cells which is an important breakthrough for solar energy harvesting.

“We tweaked the traditional flat design for luminescent solar concentrators and made them into cylinders,” said University of California, Merced Physics Professor Sayantani Ghosh, who led the solar energy project team. “The results of this architectural redesign surprised us, as it significantly improves their efficiency.”

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The main problem preventing luminescent concentrators from commercial usage is they have high rates of self-absorption, Ghosh said, meaning they absorb a significant amount of the light they produce instead of transporting it to the solar cells.

The research team showed they can address that problem by changing the shape of the concentrator. They discovered a hollow cylindrical solar concentrator is a better design compared with a flat concentrator or a solid cylinder concentrator. The hollow cylinders absorb more sunlight while having lower self-absorption losses.

Luminiscent solar concentrators should absorb solar radiation over a broad range of colors and re-emit it over a narrower range (for example, only red), a process known as down-converting. This light transports to solar cells for photocurrent generation. The quantum dots embedded in the concentrator are the materials that carry out this color conversion.

The biggest advantage they offer over traditional solar cells is they can work even in diffuse sunlight, like on cloudy days. And because of this, they do not need to directly face the sun at all times, eliminating the need for tracking mechanisms.

Ghosh said the discovery could make commercially viable luminescent solar concentrators a reality, especially because the design enhances performance while using the same number of quantum dots, therefore without being more costly.

This saves on infrastructure costs and also opens up the possibility the collectors can integrate onto vertical surfaces like walls and windows. The next step is to develop a large array of hollow cylindrical luminescent solar concentrators and track the efficiency of the panel.

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