Solar energy is intended to accelerate the transition to a clean power supply. But anyone who expands solar is not automatically protected from setbacks. Because: Air pollution can block sunlight and thus reduce yields. A study quantifies the extent to which coal aerosols slow down global solar power generation.
Solar energy plays a central role in the success of the energy transition. However, solar modules can only deliver maximum yields if sufficient sunlight hits their surface undisturbed.
Extensive data analysis now reveals an obstacle to this transformation process: air pollution caused by fine particles from coal combustion accumulates in the atmosphere and blocks solar radiation.
How strongly aerosols depress solar yield worldwide
In 2023, these so-called aerosols reduced global solar power generation by 5.8 percent (111 terawatt hours). Total climate-related energy loss, which includes both clouds and aerosols, totaled 515 terawatt hours in the same year. The total corresponds to an annual output of 84 medium-sized coal-fired power plants with a typical utilization of 70 percent.
Looking at the period from 2017 to 2023, the annual aerosol-related energy losses of existing systems (an average of 74.0 terawatt hours) were, on average, equivalent to one-third of the energy gained through new PV installations (an average of 246.6 terawatt hours per year).. Persistent air pollution thus reduces the actual benefits of global investments in solar energy.
Densely populated and industrialized regions with a high concentration of coal-fired power plants are particularly hard hit. In China, the world’s largest producer of solar power, losses from aerosols were highest in 2023 at almost eight percent. At the same time, however, China is the only region examined in which these losses have been steadily declining for several years. Strict emissions regulations for power plants have improved air quality there, even as overall coal consumption remains high.
Coal power physically interferes with solar energy
In Europe and the United States, however, there has been a slight increase in pollution-related losses. In the USA, the loss is overall lower at just over three percent, which is due to the greater spatial separation of coal and solar systems. Nevertheless, the study shows that operating both technologies in parallel has fundamental disadvantages. The researchers led by lead author Rui Song explained:
The continued use of coal-fired power plants not only poses an economic challenge to renewable energy, but also creates a direct physical barrier that degrades the performance of solar systems. The 5.8 percent global reduction in solar power generation shows that air pollution is actively undermining realized climate benefits and reducing the value of new solar investments.
The exact composition of the performance-disrupting particles in the atmosphere points directly to coal-fired power generation as the main cause. Sulfur aerosols, which are primarily produced by the combustion of this fossil fuel, are responsible for almost half of all pollution-related losses in solar power generation.
What does the coal phase-out mean for solar production?
If coal-fired power plants were taken off the grid, not only would general greenhouse gas emissions be reduced. The cleaner air would also immediately allow more sunlight through, meaning existing solar systems could provide noticeably more electricity.
This close connection makes it clear that simply adding solar capacity is not enough to achieve the goals set. The installed nominal power alone does not reflect how much climate-friendly electricity actually reaches consumers.
As a result of the study, a consistent exit from coal-fired power generation would remain essential in order to utilize the full potential of solar energy. Future energy planning must take these interactions into account so that the hoped-for climate benefits can be fully realized in the future.
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