Severe air pollution in China is blocking sunlight, significantly reducing the country’s output of solar energy, according to a Princeton University-led study.

As the world’s largest greenhouse gas emitter, China is rapidly expanding its solar-power supply in an attempt to meet 10% of the nation’s electricity needs with solar energy by 2030.

But the study shows that in the most polluted areas of northern and eastern China, aerosol pollution is reducing the potential for solar electricity generation by as much as 35%. Winter is the season with most disruption, when air pollution blocks about 20% of sunlight from reaching solar panel arrays, on average.

Expanding solar energy production could reduce reliance on fossil fuels, cutting down on the emissions that hamper solar power production and creating a “virtuous cycle,” the researchers said. This would send more solar electricity into the grid — which, in turn, should further reduce the need for fossil fuels.