Pollution from coal-fired power plants that can block sunlight is significantly cutting global solar output, and potentially causing an overestimation of climate progress, according to a new study.
Aerosols — tiny particles released from the burning of fossil fuels as well as natural sources like volcanoes — reduced global solar generation by 5.8% in 2023, researchers from the University of Oxford and University College London said in a study published in Nature Sustainability Friday. That’s equivalent to about 111 terawatt-hours of electricity, which is on par with the annual power generation of 18 medium-sized coal plants.
The effect is most pronounced when solar facilities are located next to coal plants. In China, the world’s largest producer of solar power and coal, aerosols slashed photovoltaic output by 7.7%, with scientists attributing nearly a third of the decline to coal-fired power plants. Aerosols also cut solar output in India, the US and Japan.
“When people make energy transition projections, they estimate solar electricity generation and translate that directly into climate benefits or avoided warming,” said Rui Song, a postdoctoral researcher at Oxford and the report’s lead author. “What our study shows is that there’s a risk we may be overestimating the climate benefits of solar if we do not get pollution from coal power under control.”
The findings also suggest that the logistical advantages of co-locating solar farms next to coal-fired plants — which can enable developers to quickly plug into grid connections and high-capacity transmission lines — come with a downside and can significantly curtail solar capacity.
Solar, wind and other renewables made up 34% of global electricity generation last year, overtaking coal’s 33% share for the first time since 1919, when worldwide power demand was only a fraction of current levels, energy think tank Ember said in a report last month. Despite that progress, coal remains a critical part of the energy mix, particularly in many growing economies including China, India and Southeast Asia.
At the same time, solar generation is emerging as a cheap, locally produced source of clean energy that can help shield nations from the impact of fossil fuel price spikes and volatility.
Pakistan’s rapid adoption of solar over the past few years will save the country at least $6.3 billion this year by reducing the need for oil and gas purchases, a March analysis by Renewables First and the Centre for Research on Energy and Clean Air found. But the Oxford study found aerosols — which can also originate from vehicle emissions and industrial processes like brick kilns — curbed the nation’s solar output by 15.1% in 2023.
Photograph: Solar panels in India; source: Sumit Dayal/Bloomberg
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