Q&A: Can the silicon in solar panels be reused to make new solar cells?
We’ve written before about some solar panel recycling programs. One of our readers, however, has asked us to elaborate. Erik Hessenius writes:
“Can the silicon be reused in additional new solar cells? If not (due to exhaustion of desirable properties), can it be used in the steel industry, like as the reactant used to remove undesirable oxygen in the liquid steel? How about the tempered glass; is that also exhausted of its usefulness? Can it be ground up to be added to new virgin material?”
The answer to Erik’s multi-faceted question starts out with a simple…Yes. Silicon in solar cells is most definitely recyclable, although I wouldn’t recommend putting old panels out at the curb on trash day.
Getting the Wafers Wet
The most valuable component of the conventional solar cell is silicon, the semiconductor that facilitates the absorption and conversion (to electricity) of sunlight. Through a wet-chemical treatment process, solar cell manufacturers can clean the silicon for reuse in new solar panels. The silicon wafers are wetted via that chemical process and “etched” free of dust, soiling agents, etc. These rather complex series of steps can actually return the seemingly degenerate silicon wafer to its original purity.
The only hang-up? Each manufacturer uses their own techniques to produce virgin silicon wafers and therefore must recycle their own solar cells. In other words, the odds are that if you purchase a solar panel containing Solar World materials, it would have to be returned specifically to that company for recycling. So no mass solar cell recycling plants are here yet. Perhaps a universal (enough) manufacturing process will arise somewhere soon, by the time current solar panels have run their course. In the meantime, however, most solar companies have set up recycling programs by which they’ll retrieve and recycle used or broken solar panels at their own expense.
Silicon recyclers claim ‘like new’ results for the clean and etched silicon wafers, which are then sent right back into line for future use.
The Module
The other components of a solar panel are the tempered glass and frame parts. These components are carefully separated from the solar cells, disassembled, and channeled into their respective recycling programs. Glass, metal, and plastic are individually recyclable. I have no knowledge of any of these products being passed onto other industries, although that may very well be possible. I imagine that the current, more universal, method of recycling is far more cost effective. So yes, the tempered glass and other parts of the solar module are recycled into new materials.
Other Solar Cells
Thin film solar cells, such as cadmium telluride (CdTe) and selenium cells, are also recyclable by the manufacturer. See First Solar, the largest thin film producer in the United States, for a generous example.
Posted on January 23rd in Solar Information by Dan.