Fraunhofer Institute creates proficient solar cell ‘recycling’ process

For what could be a major breakthrough for the PV recycling industry, the Fraunhofer Center for Silicon Photovoltaics CSP in Germany has developed a solution to recycle PV modules on an industrial scale and reuse the silicon to produce new PERC solar cells. The institution has developed this in close cooperation with Fraunhofer Institute for Solar Energy Systems ISE and Reiling GmbH & Co. KG. Reiling is the largest German recycling company for PV modules.

In the process, solar cell fragments are separated and collected from by-products of the mechanical recycling process which is already established. The cell fragments with sizes from 0.1 to 1 millimeter are first freed from the glass and plastic by various sorting processes employed by Fraunhofer CSP.

Thereafter, step-by-step removal of the backside contact, silver contacts, anti-reflective layer and emitter by wet chemical etching is done in a sophisticated way. The silicon is thus extracted. The metal cleaned is then converted into monocrystalline or quasi-monocrystalline ingots in standard processes. They are then converted into wafers.

This crystallization is carried out with completely recycled silicon. There is no application of commercial ultrapure silicon. The wafers created from the recycled silicon are fabricated into PERC solar cells.

Fraunhofer CSP says that with this process, it is possible to recycle all crystalline silicon PV modules, no matter how they were manufactured and what’s their origin. Today, PV recycling is mostly about plugging discarded modules into the reprocessing streams for aluminum, copper and glass. Silicon is the most used metal in the manufacturing of the solar cells and they remain at distance from recycling. Now the German researchers say that they are ready to change this equation.

Dr. Peter Dold, Project Manager at Fraunhofer CSP, says “If this were not the case, then this would be far too much work for the recycling companies. It was important for us to develop a scalable process that makes economic sense. A lot is possible in the lab, but our new process should prove itself in the practice for the recycling industry.”

The institution claims that in the first trial, the solar cell conversion efficiency was 19.7%. Dr. Dold says, “This is below the efficiency of today’s premium PERC solar cells, which have an efficiency of around 22.2 percent, but it is certainly way above that of the solar cells in the old, discarded modules.” The methodology has led to immense expectations as far as the circular economy is concerned.

Researchers call it a timely development for the world and Germany in particular. In Germany, most PV systems were installed in the period of 2009 – 2011 when the first wave of PV expansion took place. About 10,000 tons of silicon in discarded PV modules end up in the recycling market annually in Germany today. Industry experts say that this junk will rise to several hundred thousand tons per year by the end of this decade.

“It is necessary to establish adequate processes and procedures for recovering the silicon material from the discarded modules at an early stage,” adds Dr. Andreas Bett, Institute Director of Fraunhofer ISE.