Credit: Map by Eviatar Bach CC BY 4.0
Large-scale wind and solar installations in the Sahara would increase precipitation, a new study finds.

Scientists want to power the world with solar and wind energy, a feat they say is possible with large-scale wind and solar farms. Now, an international team of researchers says that building such an energy factory in the Sahara desert would come with a surprising boon: more rainfall.

Wind and solar farms are known to have local effects on heat, humidity and other factors that may be beneficial—or detrimental—to the regions in which they are situated. A new climate-modeling study finds that a massive wind and solar installation in the Sahara Desert and neighboring Sahel would increase local temperature, precipitation and vegetation.

The experts used computer climate modeling of the effects of building large renewable power installations in the barren region. They found that wind farms could double the daily amount of rainfall by mixing warmer air from above with cooler air below.

“Previous modelling 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 behaviour.”

– Yan Li of the University of Illinois at Urbana-Champaign, US.

With that in mind, Li and colleagues included vegetation response in their models. They were among the first to take this approach for wind and solar farms. The simulated renewable energy plants would cover more than 9 million square km; the wind farms would generate an average of around 3 terawatts of electrical power and the solar farms around 79 terawatts.

“Our model results show that large-scale solar and wind farms in the Sahara would more than double the precipitation, especially in the Sahel, where the magnitude of rainfall increase is between 20mm and 500mm per year,”

“As a result, vegetation cover fraction increases by about 20%.”

– Dr Yan Li

Solar farms also boosted temperature and precipitation in the models. Solar panels with a conversion efficiency of 15% reduced the albedo — reflectivity – of the land surface so that it absorbed more heat, increasing rainfall by around 50%. Solar panels with an efficiency of 30% would have a negligible effect on albedo, according to the team.

The authors also looked at other desert locations in different parts of the world but they found the impact on rainfall and vegetation growth was much smaller. They also believe that fewer panels and turbines would have a limited effect.

So it’s a win-win with vast amounts of clean energy, plus a more habitable landscape, with viable agricultural and economic development, plus more greenery over a large area that could become a significant carbon sink.

Reference:

Yan Li et al. Climate model shows large-scale wind and solar farms in the Sahara increase rain and vegetation. Science 6 september 2018. DOI: 10.1126/science.aar5629