Energy generation by wind and solar farms could reduce carbon emissions and thus mitigate anthropogenic climate change. A new climate-modeling study, published in the journal Science, finds that large-scale installations of wind and solar farms in the Sahara Desert and the neighboring Sahel region — areas particularly desirable for such farms because of their vastness and lack of inhabitants — would increase local temperature, precipitation and vegetation.
Models suggest that massive wind and solar farms, which are being evaluated to replace traditional power generation, have the potential to produce climate change at continental scales.
Yet, so far, the way wind and solar farms — the panels and infrastructure of which would cover wide swaths of land if more widely implemented — could alter vegetation and regional climate processes has not been thoroughly evaluated.
Dr. Yan Li, a postdoctoral researcher at the University of Illinois at Urbana-Champaign, and co-authors sought to more comprehensively explore the impact of solar and wind farms in the Sahara Desert and Sahel.
“Our study is among the first to model the climate effects of wind and solar installations while taking into account how vegetation responds to changes in heat and precipitation,” Dr. Li said.
“Previous modeling studies have shown that large-scale wind and solar farms can produce significant climate change at continental scales. But the lack of vegetation feedbacks could make the modeled climate impacts very different from their actual behavior.”
The wind and solar farms simulated in the study would cover more than 9 million km2 and generate, on average, about 3 terawatts and 79 terawatts of electrical power, respectively.
“In 2017, the global energy demand was only 18 terawatts, so this is obviously much more energy than is currently needed worldwide,” Dr. Li said.
The model revealed that wind farms caused regional warming of near-surface air temperature, with greater changes in minimum temperatures than maximum temperatures.
“The greater nighttime warming takes place because wind turbines can enhance the vertical mixing and bring down warmer air from above,” the researchers said.
“Precipitation also increased as much as 0.25 mm per day on average in regions with wind farm installation.”
“This was a doubling of precipitation over that seen in the control experiments. In the Sahel, average rainfall increased 1.12 mm per day where wind farms were present,” Dr. Li said.
“This increase in precipitation, in turn, leads to an increase in vegetation cover, creating a positive feedback loop.”
Solar farms had a similar positive effect on temperature and precipitation. Unlike the wind farms, the solar arrays had very little effect on wind speed.
“We found that the large-scale installation of solar and wind farms can bring more rainfall and promote vegetation growth in these regions,” said co-author Dr. Eugenia Kalnay, from the University of Maryland.
“The rainfall increase is a consequence of complex land-atmosphere interactions that occur because solar panels and wind turbines create rougher and darker land surfaces.”
“The increase in rainfall and vegetation, combined with clean electricity as a result of solar and wind energy, could help agriculture, economic development and social well-being in the Sahara, Sahel, Middle East and other nearby regions,” said co-author Dr. Safa Motesharrei, also from the University of Maryland.
Yan Li et al. 2018. Climate model shows large-scale wind and solar farms in the Sahara increase rain and vegetation. Science 361 (6406): 1019-1022; doi: 10.1126/science.aar5629