Concentrated Sunlight Earns Environmental Award

A multijunction solar cell-based concentrator photovoltaic system that captures nearly all of the sun’s energy is one of two photovoltaic technologies to win a national environmental award.

Earning a €500,000 Deutsche Bundesstiftung Umwelt (DBU) German Environmental Award is a concentrator photovoltaic module developed by Dr. Andreas Bett of the Fraunhofer Institute for Solar Energy Systems ISE and Hansjörg Lerchenmüller, general manager of Soitec Solar GmbH.

Based on multijunction solar cells, the device consists of stacked layers of gallium indium phosphide, gallium indium arsenide and germanium, which convert almost twice as much sunlight into electricity than do conventional silicon-based systems. The team achieved efficiency equal to 39.7 percent four years ago and 41.1 percent three years ago. (See: Fraunhofer Bests Own Solar-Cell Number)

Dr. Andreas Bett (left) of Fraunhofer ISE with Hansjörg Lerchenmüller of the Soitec Co. received the German Environmental Award 2012. Courtesy of Fraunhofer ISE/Soitec.

It is costly to produce triple-junction solar cells to capture all wavelengths of the sun. Instead, to produce affordable multijunction solar cells, the researchers put a lens in front of each cell, exponentially bundling the sunlight. The 3-mm-diameter semiconductors are now sufficient enough to catch focused beams of light, the scientists said.

“The use of low-cost focusing optics fosters an economical use of otherwise expensive semiconducting materials,” Bett said. “Depending on the concentration factor, you only need one five-hundredth to one one-thousandth of the semiconducting material — but you can still elevate the efficiency of the solar cell.”

The technology was first developed by The Concentrix Co., which was founded in 2005 in Freiburg to facilitate its industrial application. The spinoff was later acquired by Soitec, which brought the concentrator PV module design to serial production. It currently has a 30 percent degree of efficiency, which Bett and Lerchenmüller intend to increase over the next few years.

The modules, which require direct solar radiation, are suitable for solar parks in southern Europe, North Africa, the American Southwest and the Middle East.

A photovoltaic inverter developed by Günter Cramer of SMA Solar Technology AG also received the 2012 environmental prize.

The DBU award is one of Europe’s most highly endowed environmental prizes. Since 1993, the organization has honored various individuals for their contributions and dedication to environmental protection.

For more information, visit: www.dbu.de, www.ise.fraunhofer.de or www.soitec.com