Pollution from coal-fired power stations may be reducing global solar electricity generation by nearly 6%, with emissions from fossil fuel plants directly undermining the performance of nearby solar photovoltaic (PV) systems, according to new research led by the University of Oxford and University College London.
The study, published in Nature Sustainability, used satellite imagery, atmospheric observations and modelling to assess more than 140,000 solar PV installations worldwide. Researchers estimated that aerosol pollution — tiny particles suspended in the atmosphere — reduced global solar electricity output by 5.8% in 2023.
According to the researchers, that equates to around 111 terawatt-hours (TWh) of lost electricity generation, roughly equivalent to the annual output of 18 medium-sized coal-fired power plants.
The study suggests the issue represents a significant and often overlooked constraint on the global energy transition, particularly in regions where coal generation and solar deployment are expanding simultaneously.
Between 2017 and 2023, newly installed solar PV capacity added an average of 246.6 TWh of electricity generation each year, while aerosol-related losses from existing systems averaged 74 TWh annually — equivalent to almost one-third of the gains from new solar installations.
Lead author Dr Rui Song, from the Department of Physics at Oxford and the Mullard Space Science Laboratory at UCL, said: “We are seeing rapid global expansion of renewable energy, but the effectiveness of that transition is lower than often assumed. As coal and solar expand in parallel, emissions alter the radiation environment, directly undermining the performance of solar generation.”
Researchers traced the origins of aerosol pollution affecting solar installations and identified coal-fired power generation as a major contributor.
The effect was found to be particularly significant in China, where coal and solar infrastructure have expanded rapidly and are frequently located close together.
China generated 793.5 TWh of solar PV electricity in 2023 — accounting for 41.5% of global solar production — but also experienced some of the highest aerosol-related losses, with solar output estimated to have been reduced by 7.7%.
The researchers estimate that approximately 29% of aerosol-related solar PV losses in China are directly linked to emissions from coal-fired power plants.
Coal combustion releases fine particulate pollution that scatters and absorbs sunlight before it reaches solar panels, reducing electricity generation.
Dr Song said: “Air pollution doesn’t just block sunlight – it also changes clouds, which can cut solar power even further. 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.”
Despite the findings, the study noted that China was also the only major region to show sustained improvements over the past decade.
Researchers found aerosol-related solar PV losses in China declined by an average of 0.96 TWh per year between 2013 and 2023, which they attributed to stricter air pollution controls and wider deployment of ultra-low-emission technologies at coal-fired plants.
To carry out the study, researchers combined satellite imaging and machine-learning techniques to identify and map solar installations worldwide before integrating the data with atmospheric observations and solar energy modelling.
Professor Jan-Peter Muller of the Mullard Space Science Laboratory at UCL said: “Global satellite imaging enabled us to map the inexorable rise of cheap non-polluting solar power during daylight hours. In the near future, we will be able to observe the impacts of dust and smoke particles on reducing solar energy at the Earth’s surface in real-time every 10 minutes from geostationary satellites spanning the Earth.”
The study also warned that overlooking pollution-related solar losses could lead governments and businesses to overestimate renewable energy output when planning decarbonisation strategies.
Co-author Dr Chenchen Huang of the University of Bath said: “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. To stay on track, policies must account for this hidden drag and shift fossil-fuel subsidies away from coal.”
Professor Myles Allen, founder of Oxford Net Zero and a professor in Oxford’s Department of Physics who was not involved in the study, said the findings highlighted broader hidden costs associated with coal power.
“All scenarios that meet the goals of the Paris Agreement show a rapid transition away from unabated coal, which isn’t happening,” he said. “The reason is that coal power is still remarkably cheap – as this study shows, that’s because the real costs are hidden.”
Researchers added that while aerosol-related impacts are relatively moderate in the UK compared with more heavily polluted regions, the findings underline the importance of integrating air quality, energy infrastructure and climate policy when planning future renewable energy systems.
