Light-concentrating Solar Modules

Plastic replaces expensive silicon

The new technology gives hope to the solar industry, which is under pressure from the high costs of raw materials. Indeed the price for solar technology has fallen sharply recently due to the falling demand resulting from  the crisis, but PV are still unable to compete with conventional energy sources due to the high manufacturing costs. Solaria’s concentrator model brings PV a step closer to being competitive. “We are lowering costs, by replacing expensive silicon with plastic,” says Kunze. With conventional cells, silicon covers the entire surface, capturing the light over the entire area. The Americans are now cutting conventional cells made of multicrystalline silicon into 74 individual, two-millimetre wide strips and arranging these with the same gap in between. In the gaps, the company is positioning plastic lenses which catch the light and then guide it to the cells with double the concentration. “We are getting by with half the amount of silicon and producing two cells from one,” explains Solaria technical manager Kevin Gibson.

Even if it seems uneconomical to saw up finished components and then assemble them again, the approach is saving money as the total costs for plastic and the new process steps is lower than that of conventional cells, according to Gibson. In addition, Solaria is using tried-and-tested machines from semiconductor production and doing away with expensive specialised equipment, which means additional cost savings can be expected.

Despite tried and tested production technologies, Solaria still sees potential for improvement when it comes to the manufacturing process. It is also one of the reasons why the company will inform itself on the new developments in this area at the solarpeq; the trade fair for solar production technology, which will take place in Düsseldorf from 28 September until 01 October. “We set our hopes high to get much input from the solarpeq”, stated Kunze. Solaria’s basic approach has also convinced the PV concern Q-Cells, who wants to purchase 1,350 MW cells from the Americans by 2017.  Nevertheless, Solaria has to reckon with fierce competition, because many companies are working on cost-reducing concentrator technologies.

However, in comparison with Solaria, most of the concepts are based on a considerably stronger concentration of light. Concentrix Solar, for example, a spin-off foundation of the Fraunhofer Institute for Solar Energy Systems, is producing modules, whose lenses steer light, intensified  almost 385 times, to tiny multi-stacked cells with an efficiency of more than 37 percent. The company wants to push conventional PV modules from the market with these, especially in sunny regions. “In countries with high solarisation, the technology works up to 20 percent more efficiently than conventional solar systems,” says Concentrix boss Hansjörg Lerchenmüller.

However, production is laborious: So that the focus of each lens is positioned exactly on the relevant cell, both components must be aligned with no more than 25 micrometres of deviation from the ideal value. In this way, Concentrix can use cells which are smaller than a fingernail, and it is even worth installing expensive high-efficiency cells. As the lenses only work with direct solarisation, they are fitted to so-called trackers which track the sun exactly. But high system efficiencies justify the cost: Under the southern sun, the technology converts 25 percent of light into energy – twice as much as conventional PV systems. Concentrix is currently constructing its first power stations in Spain and the USA.