NREL Develops Machine that Discards Broken PV Wafers
When we think about improving the affordability and availability of solar panels, the first thing that usually comes to mind is the raw improvement of its efficiency. However, as it is an artificial product manufactured by man, we can already improve its overall value by just making the manufacturing process more efficient and cost effective.
The U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) has the primary concept in mind, when they developed this special yet very simple mechanical tool that can improve the number of quality solar panels that are being made.
The manufacturing procedure required to fabricate solar panels is a multi-stage process that practically stresses out silicon wafers. Within the assembly lines, the solar PV wafers are diffused, etched, layered, and are subjected to many other sub-processes just to prepare them to become the panels that we use. According to the report, around 5 to 10% of the PV wafers never practically make it through the process. The wafer is still in one piece, but the micro-cracks that have formed throughout the wafer render it technically unusable, and it eventually breaks when they are finally formed into solar cells.
In answer to this efficiency problem, NREL has developed a simple yet effective machine that would segregate the whole, undamaged PV wafers from the cracked and unusable ones. The machine would test the PV wafer by subjecting it to a certain amount of temperature-based stress. If the machine detects a weak PV wafer, it would then promptly discard it before it is even taken to the primary manufacturing process (of turning it into a solar cell). The device is named as the Silicon Photovoltaic Wafer Screening System (SPWSS), and is a cube furnace with a size and area of about 15 inches on each side. It is the brainchild of NREL scientist Bhushan Sopori, and was developed along with Prakash Basnyat and Peter Rupnowski.
The design of the SPWSS was supposedly done to easily integrate itself into any typical assembly line. But apart from that, the stress testing “mechanism” of the device can be easily changed and calibrated to meet the testing requirements of the solar cell manufacturer. The temperature stress factors can be conveniently altered to higher or lower levels in case the manufacturer’s solar cells are thicker/thinner or is “configured” differently. Regardless of calibration though, it is generally capable of screening 1,200 wafers in a single hour.
There two versions of the SPWSS. The first, manual version costs about $60,000. The second version automatically separates broken wafers, although the added hardware increases the cost to $100,000.
More info about NREL’s device in this official link.
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