New research led by the University of Oxford and University College London (UCL) has revealed that pollution from coal-fired power plants is reducing the energy output of solar PV installations, particularly where these power plants are expanding side by side.
Credit: Michael Pointner/Pixabay
The new study mapped and assessed more than 140,000 solar PV installations worldwide using satellite data. By combining this with atmospheric data on air pollution, the researchers calculated how much sunlight is lost and how this reduces electricity generation. They found that aerosols, which are tiny particles suspended in the air, reduced global solar electricity output by 5.8% in 2023.
That is about 111 TWh of lost energy, the amount of energy generated by 18 medium-sized coal-fired power plants.
Between 2017 and 2023, new PV installations added an average of 246.6 TWh of electricity each year, while aerosol-related losses from existing systems reached 74.0 TWh annually. That’s nearly one-third of the gains from new PV capacity.
“We are seeing rapid global expansion of renewable energy, but the effectiveness of that transition is lower than often assumed,” said Rui Song, lead author of the study with Oxford’s department of physics, and the Mullard Space Science Laboratory at UCL. “As coal and solar expand in parallel, emissions alter the radiation environment, directly undermining the performance of solar generation.”
To identify the sources of these aerosol-related losses, the researchers traced their origins and found coal-fired power generation to be a major contributor. This effect is particularly evident in China, where solar and coal capacity have expanded in parallel and are often co-located. Regions with high coal capacity aligned closely with areas experiencing the greatest solar PV losses, according to the study. However, simultaneously, the study found that China’s aerosol-related losses have declined by 0.96 TWh annually between 2013 and 2023.
According to the study, the United States hasn’t experienced as large of a loss in solar output due to coal pollution as, because coal and solar power plants are not often located near one another in the country. Overall, U.S. solar output was cut by 3.1% during that 2013 to 2023 period.
However, overall U.S. solar output is decreasing by 1.5% annually due to aerosol-related pollutants. The study states that: “The U.S. case demonstrates that the aerosol-induced performance barrier is not an inherent property of solar power, but is a direct consequence of the proximate operation of coal-fired power plants, a barrier that would be removed by their phase-out.”
“Air pollution doesn’t just block sunlight – it also changes clouds, which can cut solar power even further,” Song said. “That means the real impact is likely to be bigger than we’ve measured, so we may be overestimating how much solar power can contribute to reducing emissions if we do not get pollution from coal power under control.”
To carry out the analysis, the researchers combined satellite imagery and machine learning to identify and map more than 140,000 solar installations worldwide. They then integrated these data points with atmospheric observations and a solar energy model to estimate how much electricity each site generates and how much is lost due to air pollution.
“Our findings send a clear warning to the sustainable development goals: overlooking pollution-induced solar energy losses can lead to a systematic overestimation of renewable energy output by governments, businesses and the broader community,” said Chenchen Huang with the University of Bath, a co-author of the study. “To stay on track, policies must account for this hidden drag and shift fossil-fuel subsidies away from coal.”
News item from the University of Oxford
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