Blocked sunlight and changing clouds: How coal pollution is damaging our solar potential
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Scientists warn that solar capacity is being damaged, as the world clings to polluting coal power.
Solar has been described as a “shining star” of the EU’s clean transition, but scientists warn that coal pollution is damaging renewables’ capacity to slash emissions.
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New research led by the University of Oxford and University College London (UCL) mapped and assessed more than 140,000 solar photovoltaic (solar PV) installations worldwide.
The study, published in the science journal Nature Sustainability, uses satellite and atmospheric data on air pollution to calculate how much sunlight is lost and how this reduces electricity generation.
Researchers found that pollution from coal-fired power plants “significantly reduces” the energy output of solar PV installations, particularly where these are expanding side by side.
How coal pollution is harming solar output
The study warned that aerosols (tiny particles suspended in the air) reduced global solar electricity by 5.8 per cent in 2023.
This is equivalent to 111 terawatt-hours of lost energy - the amount generated by 18 medium-sized coal-fired power plants. To put that into perspective, one terawatt-hour is about the same as the annual electricity consumption of 150,000 EU citizens, according to Our World in Data.
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 TWh annually - equivalent to nearly one-third of the gains from new capacity, the report adds.
RelatedResearchers argue that this highlights a “previously unrecognised interaction” between fossil fuel use and renewable energy, where emissions from one system directly impact the performance of the other.
“We’re seeing rapid global expansion of renewable energy, but the effectiveness of that transition is lower than often assumed,” says lead author Dr Rui Song.
“As coal and solar expand in parallel, emissions alter the radiation environment, directly undermining the performance of solar generation.”
Why are coal power plants bad news for renewables?
Coal is considered the dirtiest, most polluting way of producing energy, and is one of the main drivers of global warming. Despite renewables overtaking fossil fuel power for the first time last year, many countries are still clinging to coal power plants despite their environmental harm.
Just last month, Italy announced it was postponing the permanent shutdown of its coal-fired power plants until 2038, 13 years later than its initial deadline. Environmental groups and the centre-left opposition criticised the move, with the leader of the Europa Verde green party, Angelo Bonelli, accusing the government of “climate neglect”.
Coal plants emit fine pollution particles that scatter and absorb sunlight, which reduces the amount that reaches nearby solar panels. Dr Song explains that air pollution doesn’t just block sunlight, but 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,” he adds.
This effect was 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.
China is the world’s largest solar producer, and generated 793.5 TWh of solar PV electricity in 2023 (41.5 per cent of the global total). But it also experienced the largest losses from aerosols, with total output reduced by 7.7 per cent.
Researchers estimate that around 29 per cent of aerosol-related solar PV losses in China come specifically from coal-fired power plants.
Co-author Dr Chenchen Huang, from the University of Bath in the UK, says the report’s findings send a “clear warning” that 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,” Dr Huang adds.
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