The world is in the midst of a renewable energy revolution, with solar power leading the charge. But a new study from the University of Oxford and University College London (UCL) reveals a hidden obstacle to this transition: coal pollution. This pollution is not only detrimental to the environment but also significantly reduces the effectiveness of solar power installations, particularly in regions where coal and solar capacity are expanding in parallel.
What makes this finding particularly fascinating is the scale of the impact. The study found that aerosols, tiny particles suspended in the air, reduced global solar electricity output by 5.8% in 2023, which is equivalent to the energy generated by 18 medium-sized coal-fired power plants. This is a staggering loss, especially considering that new PV installations added an average of 246.6 TWh of electricity each year between 2017 and 2023, while aerosol-related losses from existing systems reached 74.0 TWh annually, nearly one-third of the gains from new PV capacity.
One thing that immediately stands out is the role of coal-fired power plants. The study traced the origins of these aerosol-related losses and found that coal-fired power generation is a major contributor. This effect is 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, according to the study.
However, the study also found that China’s aerosol-related losses have declined by 0.96 TWh annually between 2013 and 2023. This is a positive development, but it also raises a deeper question: why are some countries experiencing more significant losses than others? In my opinion, the answer lies in the proximity of coal and solar power plants. In the United States, for example, coal and solar power plants are not often located near one another, which has led to lower losses in solar output.
What many people don't realize is that air pollution doesn’t just block sunlight – it also changes clouds, which can cut solar power even further. This means that the real impact of coal pollution on solar power is likely to be bigger than we’ve measured. In fact, the study suggests that we may be overestimating how much solar power can contribute to reducing emissions if we do not get pollution from coal power under control.
If you take a step back and think about it, this finding has significant implications for 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.
In my view, this study sends a clear warning: the effectiveness of the renewable energy 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. To truly harness the potential of solar power, we must address the pollution caused by coal-fired power plants. This is not just an environmental imperative but also an economic one, as the transition to clean energy is essential for a sustainable future.
