PHOTON International The Photovoltaic Magazine

Concentrix to produce concentrator modules

A spin-off from Fraunhofer ISE intends to combine the age-old technique of focusing sunlight onto small cell surfaces with innovative cell technology to produce commercially competitive concentrator modules.

	© Martin Sachse for photon-pictures.com
»The right moment«: As managing director of the newly founded Concentrix Solar GmbH, Hansjörg Lerchenmüller plans to market the Fraunhofer Institute's concentrator modules.

A new »European record,« that's what Andreas Bett, project director at the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Germany announced in April. It's likely he would have preferred to proclaim a new world record, but this title is still held by US company Spectrolab Inc.

The record in question is that of solar cell efficiency – although this time not for the common silicon technology. Rather it's about a multiple layer cell that utilizes different parts of the solar spectrum. The ISE's monolithic cell, explains Bett, »consists of gallium indium phosphide, gallium arsenide, and germanium.« In April, the company achieved a 35.2-percent efficiency with a cell measuring 0.031 cm². Spectrolab's record stands at 36.9 percent. Although these high-efficiency cells are primarily designed to power satellites, they are also suitable for use in terrestrial concentrator modules, which focus sunlight onto an extremely small cell surface area. This process compensates for the high costs of such cells.

The concept is well-known: the pioneer in this area, US company Amonix, has offered these types of systems for some time – though with comparatively simple silicon solar cells – and is currently in negotiations with Spanish company Guascor, which plans to set up a factory for this module technology in Spain (see PI 4/2005, p. 20). Another Spanish company, cell and module manufacturer Isofoton, is also close to commercialization of a concentrator product, and a number of other companies are waiting in the wings. Even ISE has developed a similar module, which is aimed for commercialization under the name Flatcon (Fresnel lens all-glass tandem cell concentrator). The high-powered cells, measuring just 2 cm², are soldered onto copper sheets serving as a heat sink. These sheets are glued to a glass plate. Fresnel lenses made from silicone, which are attached above the cells, concentrate sunlight by 500 times onto the small solar cells.

© Martin Sachse for photon-pictures.com

Building a Flatcon module: Light is concentrated through Fresnel lenses (left) onto tiny high-powered multi-junction III-V cells.

During initial outdoor test, module efficiencies of 22.7 percent were achieved, whereby in this case only tandem cells with efficiencies of 32 percent were used. If the higher quality triple cells are applied, module efficiency will rise to above 25 percent, and will perhaps reach as high as 28 percent, hopes Hansjörg Lerchenmüller, managing director of Concentrix Solar GmbH, an ISE spin-off, in charge of commercializing the Flatcon project.

As concentrator modules can only take advantage of direct sunlight, the intended markets for this product are countries with high solar irradiation. Obviously, the cells will be used in conjunction with tracking systems. ISE estimates that the technology has good chances for application in Southern European locations. For instance, in some of the most productive areas of Spain, the calculated manufacturing costs of €1.23 ($1.58) per W for the modules – of which 46 euro cents (59¢) goes for solar cells – and €2.35 ($3.03) for the complete system including inverter would result in electricity production costs of 19 euro cents (25¢) per kWh. When compared with conventional technology, this results in a cost advantage of 15 percent, perhaps even 20 percent or more in the case of desert regions of North Africa or the US.

Concentrix plans to build a pilot production line in Freiburg by the end of 2005. In the meantime, the company is looking for additional shareholders to provide the necessary capital. »All in all,« says Lerchenmüller, »we're convinced that this is the right moment to bring this technology to the market.«