by Emma Foehringer Merchant
September 10, 2019

The climate crisis is replete with ironies. Countries and people who have produced the least pollution will be the most impacted, and fossil fuel companies that caused climate change are now investing in clean energy to hedge against climate risk and make some money. 

Scientists have recently identified another troubling example: As climate change worsens, it will likely make solar energy — one of the technologies most likely to cut electricity emissions — less effective. 

Researchers at the Massachusetts Institute of Technology found that by 2100, energy output from silicon PERC PV modules could drop by 0.45 percent per degree Celsius of warming. That decline in efficiency adds up to 15 kilowatt-hours lost for an average installation in 2100, according to the research.

“It’s clear when things get warmer, solar cells start to lose power,” said study co-author Dr. Ian Marius Peters.

Reductions would be higher in some regions where warming is most severe, up to 50 kilowatt-hours per installation. According to the study, rising temperatures will cause energy output to drop across the globe, but the southern U.S., Southern Africa and Central Asia face the most significant potential impacts.

Though the study gives a better idea of how climate change may impact the technologies most suited to slow it, Peters said the temperature impact is only one part of understanding how a changing world will affect solar. Factors like humidity and insolation, which will both change alongside temperature as the world warms, are likely to further compound negative impacts on solar installations.

“One reason why I think this is significant is this is an additive effect, and it will come together with everything else,” said Peters, who is continuing to study the impact of temperature change on solar.

And that might be the optimistic take

The huge quantity of renewables piling onto the grid will also multiply the consequences of efficiency losses. To keep warming below 2°C, the upper limit of the goal set out in the Paris climate agreement, the International Renewable Energy Agency says the world must install around 8,500 gigawatts of solar PV by 2050. As countries rapidly build out solar capacity and temperature increases, even a slight loss in efficiency will require more solar panels — and money — to meet the same baseline power output. 

The results out of MIT may also be optimistic: Peters and co-author Dr. Tonio Buonassisi used a warming scenario at the lower-middle of possible models that forecast how climate change could unfold.

Called Representative Concentration Pathway 4.5, the scenario projects a future in which emissions peak by 2040, the concentration of carbon dioxide in the atmosphere reaches 540 parts per million by the end of the century and temperature increases 1.8°C from 2000 levels. 

The most severe Representative Concentration Pathway developed by modelers forecasts carbon dioxide reaching 940 parts per million by 2100 and temperatures increasing 3.7°C. Peters and Buonassisi forecast that solar yield reductions would likely more than double under that scenario. 

The world’s carbon dioxide concentration averaged 409.92 parts per million in 2018, per the National Oceanic and Atmospheric Administration. A report released last fall by the United Nations Intergovernmental Panel on Climate Change found that the world was scarily far from limiting warming to 1.5°C, the more ambitious lower bound of what countries agreed to in the Paris climate pact and the temperature that scientists believe will avoid the most catastrophic impacts of climate change.

Heat-induced degradation

Though the MIT research provides concrete numbers on efficiency losses, the results shouldn’t come as a huge surprise. Already today, weather has a significant impact on the output of solar panels and the functioning of balance-of-system components.

Shade, solar irradiance and seasons can all impact how much energy an installation produces. But certain conditions can also degrade solar panels faster, like extremely hot or humid environments.

Independent testing lab PV Evolution Labs examines how modules hold up in shifting temperatures using “thermal cycling,” shifting between negative 40°C and 85°C, for its yearly scoring of solar products. Those temperature changes are intended to simulate field conditions that cause solar products to expand and contract.

Though that change in size is marginal, the varied rates at which solar products grow and shrink can have significant impacts on how a solar installation holds up due to “interfacial stress,” which the lab says “reduces the strength of the bonds between each layer of the PV module” and can degrade performance. 

In a warming world, many regions are expected to become hotter and more humid. Solar installations will likely produce less and deteriorate more quickly in those areas.   

Advancements in solar technology could lessen the impact. Modules have already become increasingly efficient in recent years, possibly negating losses, as the National Renewable Energy Laboratory visualizes below.

National Renewable Energy Laboratory

Resilience of solar modules looks to be increasing as well. In its most recent module tests, PV Evolution Labs noted that even as it upped the number of temperature cycles that products endured by a quarter, performance also “clearly improved.”

Though it’s difficult to say what technological breakthroughs the solar industry will experience by the end of the century, Peters acknowledged that “the panels that are going to be installed in the year 2100 are almost certainly going to be more efficient than the ones we have around today.”

Recognizing how climate impacts solar now may allow the industry to innovate through those problems as policymakers look to rapidly increase the share of electricity coming from renewables. The electricity sector is neck-and-neck with transportation as the highest source of U.S. emissions. 

Jurisdictions such as Hawaii and Puerto Rico are targeting 100 percent renewables by mid-century and presidential candidates including Bernie Sanders and Elizabeth Warren have unveiled ambitious climate plans that would dramatically increase federal buildout of solar and wind.

Peters also notes that installing more solar has feedback benefits, a counterpoint to the horrifying feedback loops created by climate change (like ice melt reducing the reflection of the sun away from earth, which then causes sunlight to melt more ice). If we install more solar, he said, we can cut more emissions and hopefully staunch temperature increases, which in turn keeps solar from losing efficiency. 

“The results in no way mean that it doesn’t make sense to put up more solar panels — quite the opposite,” said Peters. “Decarbonizing electricity is probably the first thing we should do to put a lid on global warming.”

“It’s just another reminder of how important it is that we achieve these goals,” he added.