Solar panels present a sustainable energy solution, but their recyclability can be hindered by the use of thin plastic layers encasing the solar cells.
Researchers at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) have conducted a proof-of-concept study showing that the use of femtosecond lasers to form glass-to-glass welds for solar modules can make the panels easier to recycle.
This innovative approach eliminates the need for plastic polymer sheets that currently complicate the recycling process. At the end of their lifespan, modules made with laser welds can be shattered, allowing for easy recycling of the glass and metal wires and the reuse of the silicon. This advancement holds significant promise for enhancing the sustainability of solar energy technologies.
The use of a femtosecond laser enables the creation of a strong, hermetic seal by melting the glass together with a short pulse of infrared light. This glass weld technology is versatile and can be applied to a variety of solar technologies, including silicon, perovskites, and cadmium telluride, with the advantage of confining the weld heat to a few millimeters from the laser focus.
Solar modules, which are essential in converting sunlight into electricity, typically consist of semiconductors sandwiched between two glass sheets laminated together with polymer sheets. Research conducted by NREL demonstrated that femtosecond laser and glass/glass welds exhibit strength comparable to that of the glass itself.
“As long as the glass doesn’t break, the weld is not going to break,” said David Young, senior scientist and group manager for the High-Efficiency Crystalline Photovoltaics group in the Chemistry and Nanoscience department at NREL. “However, not having the polymers between the sheets of glass requires welded modules to be much stiffer. Our paper showed that with proper mounting and a modification to the embossed features of the rolled glass, a welded module can be made stiff enough to pass static load testing.”
Researchers say this is the first time femtosecond laser technology has been used to create glass/glass welds for solar modules. Previous attempts using nanosecond lasers and glass frit filler resulted in brittle welds unsuitable for outdoor module applications. In contrast, the femtosecond laser welds offer superior strength and hermetic sealing at a competitive cost.
According to Young, this research presents a high-risk, high-reward opportunity and sets the stage for further exploration to extend the lifespan of solar modules beyond 50 years and facilitate easier recycling.
This innovative research was conducted as part of the Durable Module Materials Consortium, led by NREL and funded by the U.S. Department of Energy’s Solar Energy Technologies Office in the Office of Energy Efficiency and Renewable Energy.
Journal reference:
- David L. Young, Timothy J. Silverman, Nicholas P. Irvin, Daniel Huerta-Murillo, Bill Holtkamp, Nick Bosco. Towards Polymer-Free, Femto-Second Laser-Welded Glass/Glass Solar Modules. IEEE Journal of Photovoltaics, 2024; DOI: 10.1109/JPHOTOV.2024.3364823
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