Coal plant pollution is quietly erasing a chunk of the world’s solar gains

Pollution is reducing solar output at global scale

Coal-fired power plants are not only prolonging the life of fossil-fuel electricity systems. New research indicates they are also undermining the performance of solar installations that are supposed to replace them. In a study published in Nature Sustainability, researchers led by the University of Oxford and University College London mapped more than 140,000 solar photovoltaic sites worldwide and paired that information with atmospheric pollution data to estimate how much power is being lost before sunlight ever reaches the panels.

The answer is not trivial. The team found that aerosols, the tiny particles suspended in air from sources including coal combustion, reduced global solar electricity output by 5.8% in 2023. That translated into 111 terawatt-hours of lost generation, roughly equivalent to the annual output of 18 medium-sized coal-fired power plants. At a moment when governments are measuring progress in gigawatts of new renewable capacity, the study argues that the atmosphere itself has become an overlooked bottleneck.

A hidden penalty on renewable expansion

The most important implication is not simply that some solar projects are underperforming. It is that fossil-fuel emissions can directly reduce the productivity of the clean-energy systems being added alongside them. Between 2017 and 2023, new photovoltaic installations added an average of 246.6 terawatt-hours of electricity each year. Over the same period, aerosol-related losses from existing systems reached 74 terawatt-hours annually, close to one-third of those gains.

That finding reframes the relationship between legacy and emerging power systems. Coal plants do not only emit greenhouse gases that worsen climate change over decades. Their pollution can also immediately suppress the output of solar arrays in the regions around them and farther downwind. In practical terms, every unit of coal generation may carry an additional cost by lowering the performance of the very infrastructure intended to displace it.

Why coal stands out

To identify which pollution sources were responsible for the losses, the researchers traced aerosol origins and found coal-fired generation to be a major contributor. The effect is especially visible in places where coal and solar have expanded in parallel. China was highlighted as a clear example, with large-scale growth in both systems creating conditions where one energy source is materially weakening the other.

Lead author Rui Song said the rapid expansion of renewables has made this interaction more consequential than many planning models assume. If emissions alter the radiation environment, then the nominal capacity of a solar buildout may exaggerate its real-world contribution. The issue is not whether solar works, but how much of its theoretical output is being silently discounted by dirty air.

What the researchers did differently

The study stands out because it does not rely on local case studies alone. By using satellite observations to identify solar assets worldwide and then combining those observations with atmospheric data, the authors created a broad estimate of how pollution is affecting power generation across regions and over time. That scale matters. It suggests this is not a niche engineering problem limited to a handful of polluted urban corridors, but a systemic issue relevant to global decarbonization planning.

For investors, grid operators, and policymakers, that means the performance gap between expected and delivered solar power may not always be explained by panel quality, maintenance, or weather variability. Air quality itself belongs in the calculation. If planners ignore aerosol effects, they risk overstating renewable output and understating the benefits of shutting down high-pollution generation first.

What it means for energy policy

The research points to a simple but politically important conclusion: cleaning the air can improve solar economics almost immediately. Retiring coal plants, tightening emissions controls, and reducing particulate pollution could increase output from existing solar fleets without building a single additional panel. In that sense, pollution control becomes a renewable-efficiency strategy as much as a public-health measure.

The paper also suggests that sequencing matters in the energy transition. Where governments add solar while allowing coal to remain heavily used, part of the benefit is clawed back by atmospheric interference. Faster coal phaseouts would therefore produce a double dividend, cutting emissions while improving the productivity of low-carbon infrastructure already in place.

There is a larger strategic lesson here as well. The clean-energy transition is often discussed as a race to install more capacity. This study argues that protecting the performance of that capacity is just as important. A megawatt of solar power does not deliver the same value in every atmospheric environment, and pollution can be a direct tax on renewable generation.

As countries chase electrification, industrial growth, and lower emissions at the same time, the message from this research is unusually concrete: the path away from coal is not only about future climate stability. It can also improve the output of today’s solar infrastructure right now.

This article is based on reporting by Phys.org. Read the original article.