A new study led by the University of Oxford and University College London, published in Nature Sustainability, shows that pollution from coal-fired power stations is measurably reducing the output of solar PV plants, particularly in regions where the two technologies have expanded side by side.
Irena: 24/7 case for renewables no longer theoretical
The team used satellite imagery and machine learning to map more than 140,000 solar installations worldwide, then combined the dataset with atmospheric observations and a validated solar energy model. The analysis quantifies how aerosols – the fine particles suspended in the air – scatter and absorb sunlight before it reaches a module. In 2023, aerosol pollution cut global solar electricity output by 5.8%, or 111 TWh, equivalent to the annual generation of 18 medium-sized coal plants.
The cumulative picture is more striking. Between 2017 and 2023, new PV installations added an average of 246.6 TWh of electricity each year, while aerosol-related losses from the existing fleet reached 74.0 TWh annually, close to a third of the gains from new capacity.
US renewable capacity set to reach 1.06 TW by 2035
“We are seeing rapid global expansion of renewable energy, but the effectiveness of that transition is lower than often assumed,” said lead author Dr Rui Song of the Department of Physics at Oxford 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.”
As the world’s largest solar producer, China generated 793.5 TWh of PV electricity in 2023, or 41.5% of the global total, and also recorded the largest losses, with output reduced by 7.7%. Around 29% of those aerosol-related losses trace back specifically to coal-fired power plants in the same regions where utility-scale PV has expanded fastest.
China is also the only major region to show a sustained improvement, with aerosol-related solar PV losses falling by an average of 0.96 TWh per year, or 1.4% annually, between 2013 and 2023. According to the study, this is due to stricter emission standards and the adoption of ultra-low-emission technologies at coal stations, rather than any reduction in coal capacity.
Negative pricing surges as EU solar outpaces grids
Co-author Dr Chenchen Huang of the University of Bath warns that ignoring the effect risks “a systematic overestimation of renewable energy output by governments, businesses and the broader community,” and argues that fossil-fuel subsidy regimes should be adjusted accordingly. Professor Myles Allen of Oxford, founder of Oxford Net Zero and not involved in the study, adds that coal remains cheap on paper because its real costs, including the drag on neighbouring renewables, stay hidden.
Aerosol loadings are lower across most of Europe, where cloud cover remains the main issue. The wider lesson still applies: capacity is not the same as delivered energy. (TF)
