High efficiency concentrator solar cells and modules

May 19, 2010
Dr. Andreas Bett and Dr. Frank Dimroth (left to right) working on highest-efficiency solar cells and concentrating solar modules to make solar energy cheaper. (© Fraunhofer / Dirk Mahler)

(PhysOrg.com) -- Solar energy will play a crucial role in the energy mix of tomorrow as solar energy is available in unlimited quantities. With the aid of concentrator solar cells, even more sunlight can be converted into electricity.

Climate change and ever scarcer fossil resources will determine the energy mix of the future. Solar energy will play an integral role in this regard. Dr. Andreas Bett and Dr. Frank Dimroth of the Fraunhofer Institute for Systems ISE in Freiburg, Germany, developed metamorphic triple-junction solar cell consisting of III-V compound semiconductors: gallium indium phosphide, gallium indium arsenide and germanium. This special structure makes it possible to optimize the use of almost the entire for energy production. Researchers have been able to transform more sunlight into power than ever before, at a record degree of efficiency of 41.1 percent. In recognition of their work, they are receiving the 2010 Joseph von Fraunhofer Prize.

This high degree of efficiency is made possible by stacking multiple top-quality solar cells on top of each other. "Our triple solar cell consists of more than 20 individual layers, all of which we have optimized," says Dr. Frank Dimroth. "We have improved both the structure of the semiconductor as well as the material quality, the metal contacts and the antireflection coatings, in order to arrive at this result."

Originally, these compound solar cells were engineered for use in space - most satellites in space are loaded with them. They supply the operating power. Since the production process is comparatively expensive, these cells had not been used on earth before. The combination of highly efficient cells with a lens amplifier ensures that - in comparison to conventional - only one five-hundredth of the semiconductor surface will be needed. The cells within their own specially designed concentrator modules measure only three square millimeters in size.

A Fresnel lens is situated over these mini solar cells, at a distance of approximately ten centimeters. This configuration concentrates the sunlight by a factor of 400 to 500. To prevent the cells from overheating, they are attached to a copper support that distributes the heat sufficiently well. Thus, passive cooling of the solar cells suffices. "Thanks to this construction, we were able to produce modules with a degree of efficiency in excess of 29 percent," says Dr. Andreas Bett. These modules have been on the market since 2007 under the brand name FLATCON®, and are being used in a solar park in Spain, for example.

To facilitate the swift transfer of technology from the laboratory to industry, a demonstration laboratory was constructed at the institute, with the same machines that would be used in industry. Here, researchers are developing and testing production processes for the construction and connection technology, module integration and quality control. A spin-off of ISE - Concentrix Solar GmbH - produces the concentrator systems that, for example, feed solar power into the grid from a solar park in Spain with 25 percent system efficiency. For the development of metamorphic triple-junction solar cells, the team has been closely collaborating for years with AZUR Space Solar Power in Heilbronn, the leading European manufacturer of solar cells for space. This partner is aiming to bring the highly efficient to the market by 2011.

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User comments : 10

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Roj
not rated yet May 19, 2010
In the last year, German solar-cell development has lost political support, since China dominates the solar panel market there. This local development may not pay back if similar market losses result from Chinese competition, intellectual property losses, & underpricing.
dirk_bruere
not rated yet May 19, 2010
$/Watt?
bfast
not rated yet May 19, 2010
dirk_bruere is absolutely right. Watts per square foot, or square meter is must less important than watts per dollar. Any engineers that don't get this have absolutely missed the point in most applications. My understanding is that solar is currently about 5 times the cost of wind.
antialias_physorg
5 / 5 (1) May 19, 2010
When I googled I found a PDF which states that the manufacturing costs are 2,35€/Watt

According to this site:
http://www.wallst...fos-ag-s

The cost per Watt (in March 2007) was 4.80€/Watt (should be a bit lower by now).

Still expensive if you compare it to other solar cell types. However if space is at a premium then these types of solar cells are the way to go.
ricarguy
2 / 5 (4) May 20, 2010
As of a few years ago, it took more energy to make, transport, install and integrate a solar power gen facility than it was expected to produce over its life. Mostly because crystalline Si is very energy intensive to make. Have we turned the corner in a mass producible PV solar technology? I would like to hope but if they can't say that, why should I think it? I assume a lens system means you have to precisely follow the sun and a cloud shuts you down.

Solar makes sense in places where you don't want to run the wires. Keep working at it guys. Some day we may have something.

These expensive solar installations have reportedly helped to bankrupt Spain. France is much more successful with even the moderately high cost of nuclear. A lesson to all, think before you jump.
JamesThomas
not rated yet May 20, 2010
My sense is that nuclear is the old paradigm.

Being bathed in the light and warmth of the Sun, motivates us to take advantage of its free gift.

Clean solar power is transforming exponentially both in efficiency and lowering of cost. Everyday we see breakthroughs. A year from now solar power generation will be significantly improved from today. Two years from now we will be amazed.....
Jimee
not rated yet May 20, 2010
It's hard to see where harvesting the sun's power will lead us in the wrong directions.
PPihkala
not rated yet May 20, 2010
Yes, everyone admits that using the sun's energy is preferable to other more polluting energy sources, but the big question is when is it affordable? It might be that in future, but currently it's quite expensive.
Sonhouse
1 / 5 (1) May 23, 2010
As of a few years ago, it took more energy to make, transport, install and integrate a solar power gen facility than it was expected to produce over its life. Mostly because crystalline Si is very energy intensive to make. Have we turned the corner in a mass producible PV solar technology? I would like to hope but if they can't say that, why should I think it? I assume a lens system means you have to precisely follow the sun and a cloud shuts you down.

Solar makes sense in places where you don't want to run the wires. Keep working at it guys. Some day we may have something.

These expensive solar installations have reportedly helped to bankrupt Spain. France is much more successful with even the moderately high cost of nuclear. A lesson to all, think before you jump.

It's energy intensive but you could use concentrated solar energy to make the heat to melt the crystals, which would make the whole process a lot more efficient.
Skeptic_Heretic
not rated yet May 23, 2010
How would concentrating solar energy for thermal use be more efficient than current thermal technology? Especially when the sun isn't constant but the foundry runs all day long.