NREL Proof of Concept Shows Path to Easier Recycling of Solar Modules
April 25 2024 - 3:18PM
The use of femtosecond lasers to form glass-to-glass welds for
solar modules would make the panels easier to recycle, according to
a proof-of-concept study conducted by researchers at the U.S.
Department of Energy’s National Renewable Energy Laboratory (NREL).
The welds would eliminate the need for plastic polymer sheets
that are now laminated into solar modules but make recycling more
difficult. At the end of their useful lifespan, the modules made
with the laser welds can be shattered. The glass and metal wires
running through the solar cells can be easily recycled and the
silicon can be reused.
“Most recyclers will confirm that the polymers are the main
issue in terms of inhibiting the process of recycling,” said David
Young, senior scientist and group manager for the High-Efficiency
Crystalline Photovoltaics group in the Chemistry and Nanoscience
department at NREL. Young is lead author of a new paper outlining
the use of laser welds for solar modules. The paper, “Towards
Polymer-Free, Femto-Second Laser-Welded Glass/Glass Solar Modules,”
appears in the IEEE Journal of Photovoltaics.
Written with NREL colleagues Tim Silverman, Nicholas Irvin, and
Nick Bosco, the paper also counts as its coauthors two employees of
Trumpf Inc., the California company that made the femtosecond laser
involved. A femtosecond laser uses a short pulse of infrared light
that melts the glass together to form a strong, hermetic seal.
The glass weld can be used on any type of solar
technology—silicon, perovskites, cadmium telluride—because the heat
of the weld is confined to a few millimeters from the laser
focus.
Solar modules are made of semiconductors designed to capture a
specific portion of the solar spectrum, harnessing sunlight to
create electricity. Typically, the semiconductors are sandwiched
between two sheets of glass laminated together with polymer
sheets.
NREL’s research showed that femtosecond laser, glass/glass welds
are essentially as strong as the glass itself.
“As long as the glass doesn’t break, the weld is not going to
break,” he said. “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.”
NREL’s research is the first to use a femtosecond laser to form
glass/glass welds for use in a module. A different type of edge
sealing using nanosecond lasers and a glass frit filler was tried
in the past, but the welds proved too brittle for use in outdoor
module designs. The femtosecond laser welds offer superior strength
with hermetic sealing at a compelling cost.
Young said the research is “definitely high risk, high reward,”
but points to a direction for further research to extend the life
of solar modules to beyond 50 years and to allow easier
recycling.
This research was done through the Durable Module Materials
Consortium, which is led by NREL and funded through the U.S.
Department of Energy's Solar Energy Technologies Office in the
Office of Energy Efficiency and Renewable Energy
NREL is the U.S. Department of Energy's primary national
laboratory for renewable energy and energy efficiency research and
development. NREL is operated for DOE by the Alliance for
Sustainable Energy LLC.
- NREL Proof of Concept Shows Path to Easier Recycling of Solar
Modules
Wayne Hicks
National Renewable Energy Laboratory
303-275-4051
Wayne.Hicks@nrel.gov