Researchers working at the forefront of an emerging photovoltaic
(PV) technology are thinking ahead about how to scale, deploy, and
design future solar panels to be easily recyclable.
Solar panels made of perovskites may eventually play an
important role amid global decarbonization efforts to reduce
greenhouse gas emissions. As the technology emerges from the
testing stages, it is a perfect time to think critically about how
best to design the solar panels to minimize their impact on the
environment decades from now.
“When you have a technology in its very early stages, you have
the ability to design it better. It’s a cleaner slate,” said Joey
Luther, a senior research fellow at the U.S. Department of Energy’s
(DOE's) National Renewable Energy Laboratory (NREL) and coauthor of
the newly published article in the journal Nature
Materials. “Pushing perovskite PV toward enhanced sustainability
makes more sense at this stage. We’re thinking about how we can
make sure we have a sustainable product now rather than dealing
with sustainability issues toward the end of its practical
life.”
The PV research community, the article noted, is in an
influential position to prioritize efforts in remanufacturing,
recycling, (aka a “circular economy”) and reliability to make
perovskite PV among the most sustainable energy sources on the
market.
"Perovskites could unlock the next evolution of high-efficiency
PV, and it is our responsibility to assure they are manufactured,
used, and recycled sustainably," said the lead author of the study,
Kevin Prince, a former graduate researcher at NREL who is now
researching perovskites at Helmholtz Zentrum Berlin in Germany.
Solar panels made from silicon dominate the industry, and while
they have enormous environmental and climate benefits, they were
not initially designed for “circularity.” The other leading solar
technology, cadmium telluride (CdTe), has had an established
recycling program from the technology’s inception partly to address
the scarcity of telluride. All forms of tech manufacturing come
with environmental costs, such as recycling challenges and the use
of potentially toxic chemicals. But perovskites are at an
inflection point, so the opportunity exists to address those
concerns now.
The most efficient circular economy begins at the design stage
and considers materials sourcing, strategizes for a long product
lifetime, and plans end-of-life management. According to the
researchers, the most representative way to assess the
environmental impacts of solar panel manufacturing is to look at
carbon emissions released during production, embodied energy,
sustainable material sourcing, and module circularity.
The journal article identifies critical sustainability concerns
for each component of a perovskite solar panel. Lead, for example,
could be diluted with other chemically similar metals, such as tin,
to lessen the amount of lead in a future panel. However, to date,
these substitutions have come at the cost of PV efficiency and
durability, requiring much more research before these proposed
semiconductors are ready to use in modules. The researchers also
suggest that expensive precious metals used in perovskite research
cells, including silver and gold, should be replaced with low-cost
alternatives, such as aluminum, copper, or nickel, for commercial
modules. They also said fluorine-tin oxide would be a more
practical material for the cell’s front electrodes rather than the
scarcer indium used in indium-tin oxide.
“We want to have the lowest amount of embodied energy in the
fabrication,” Luther said. “We want to have the lowest amount of
emissions in the fabrication. At this stage, now is the chance to
look at those components. I don’t think we have to change anything.
It’s more a matter of what decisions should be made, and these
arguments should certainly be discussed.”
The authors highlighted different ways to think about the
circularity of perovskite panels. Remanufacturing, for example,
comes into play when an old module is disassembled with the goal of
using certain parts to make a new module. Recycling, meanwhile,
calls for the conversion of waste materials into raw materials that
can then be refined and reused. One component that requires
attention is the specialized glass that provides structural support
for perovskite solar modules and offers protection from the
elements while remaining very clear to allow in a maximal amount of
sunlight. Establishing a recycling pathway for the glass will
become more critical as PV deployment grows. Glass manufacturing as
it stands today requires raw materials and is an energy-intensive
process.
Silvana Ovaitt, a PV researcher and coauthor of the paper, said
that as the electricity in the grid itself gets cleaner, the
manufacturing of the panels will also be cleaner, further reducing
emissions.
“Another concern is the transportation of the final modules and
the raw glass because those are the heaviest items," Ovaitt said.
"Local manufacturing will be a great way to reduce those carbon
impacts.”
The researchers explain that increasing PV module durability,
thereby increasing its useful lifetime, is a more effective
approach to reducing the net energy, energy payback, and carbon
emissions than designing for circularity alone. Even though a panel
can be designed with the end in mind, a longer lifespan means it
will not have to be recycled as often.
“Ultimately, we want to make them as durable as possible,”
Luther said. “But we also want to consider the aspects of whenever
that time does come. We want to be deliberate about how to take
them apart and to reuse the critical components.”
The other coauthors, all from NREL, are Heather Mirletz, E.
Ashley Gaulding, Lance Wheeler, Ross Kerner, Xiaopeng Zheng, Laura
Schelhas, Paul Tracy, Colin Wolden, Joseph Berry, and Teresa
Barnes.
The DOE Solar Energy Technologies Office funded the
research.
NREL is the DOE'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.
Wayne Hicks
National Renewable Energy Laboratory
303-275-4051
wayne.hicks@nrel.gov