Pollution from coal-fired power plants is diminishing the global output of solar energy by obstructing sunlight and altering atmospheric conditions, according to new research conducted by scientists at the University of Oxford and University College London (UCL). The study, published in the journal Nature Sustainability, found that fine particulate matter emitted by coal generation scatters and absorbs sunlight while influencing cloud formation, leading to a substantial reduction in solar photovoltaic electricity production worldwide.

The researchers estimate that this phenomenon cuts solar power generation by approximately 111 terawatt-hours (TWh) annually. To put this in context, the lost energy is roughly equivalent to the output of 18 medium-sized coal power plants, representing nearly a 6 percent decrease in global solar energy potential. These findings highlight a paradox where pollution from fossil fuel sources undermines the expansion and efficiency of renewable energy.

Data analyzed in the study spans from 2017 to 2023, a period during which new solar installations contributed an average of 246.6 TWh of electricity each year. Meanwhile, aerosol-induced reductions in output from existing solar infrastructure reached about 74 TWh annually. Dr. Rui Song, affiliated with both Oxford’s Department of Physics and UCL’s Mullard Space Science Laboratory, warned that ignoring coal-related pollution could lead to an overestimation of solar energy's capacity to reduce carbon emissions.

The research team utilized satellite observations to map over 140,000 photovoltaic solar arrays worldwide. They combined this with atmospheric pollution data to assess the impact of aerosols on solar performance by region. Among the countries examined, China experienced the largest absolute losses, with coal-induced pollution decreasing its solar power generation potential by 61.3 TWh annually—a reduction of 7.7 percent. In the United Kingdom, the reduction in solar output attributed to aerosols was around 5 percent; however, cloud cover was identified as a more significant limiting factor than pollution.

These findings suggest that continuing reliance on coal-fired power plants poses a challenge to the effectiveness of solar energy systems. Addressing air pollution from fossil fuels, therefore, is critical not only for public health and climate goals but also to maximize the benefits of solar power as countries transition towards cleaner energy sources.