Solar panels can't stand the heat

Lowering the operating temperature of solar panels by just a few degrees can dramatically increase the amount of electricity they generate over their lifetime, according to research conducted by the King Abdullah University of Science and Technology (KAUST) and published in the journal Joule. The hotter a panel gets, the lower its solar power conversion efficiency (PCE) and the faster it will degrade and fail.

The longstanding focus of photovoltaics (PV) research has been to improve solar modules’ PCE and make solar power more cost-competitive than non-renewable power generation. The higher the PCE, the better the PV system’s financial payback over its lifetime and the lower its ‘levelised cost of energy’ (LCOE).

Capturing sunlight is inherently hot work — panels can regularly reach 60–65°C — but heat’s impact on LCOE rarely receives much consideration. KAUST researchers developed a metric that directly compares the LCOE gains by reducing the module temperature with the LCOE gains for improving module efficiency.

Under typical operating conditions, the same improvement in LCOE by finding a hard-won 1% gain in PCE could be achieved by lowering the module temperature by as little as 3°C, the team showed. The key factor was that hotter panels fail far more rapidly.

“All solar cells generate heat, which can lower the electrical output and shorten the module lifetime,” said postdoctoral researcher Lujia Xu.

“A 4°C decrease in module temperature would improve the module time to failure by more than 50%, and this improvement increases to over 100% with a 7°C reduction.”

The team then developed a model to first predict the module temperature and subsequently find ways to lower it. The most effective approach was to locate modules in a windy environment with proper mounting to enable effective heat transfer to the surrounding environment.

They also showed they could achieve significant gains by making modifications at the module level, noting that the EVA polymer encapsulant used to seal the module strongly absorbs heat from sunlight. “Replacing EVA with a more transparent material, or even adapting an encapsulant-free module technology, would be beneficial,” Xu said.

“Our results show that researchers should pay more attention to module temperature,” said team leader Stefaan De Wolf. “Because crystalline silicon solar-cell efficiency is approaching the practical upper limit, it is timely to consider other ways to decrease the LCOE, which might be even more significant than further marginal gains in cell efficiency.”

Image ©Xu et al, 2021.

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