Sahara Wind and Solar Farms Could Green the Desert in More Ways Than One
But models have shown that large solar or wind farms could also change the climate directly by their presence.
Now, a group of scientists led by researchers at the University of Maryland and the University of Illinois set out to model what would happen if solar and wind farms large enough to power the planet were installed in the Sahara desert, and uncovered a form of climate change that might actually help more than it hurts.
The results, published Friday in Science, found that the installations would increase rainfall and vegetation in the Sahara and neighboring Sahel region, which lies between the Sahara and the Sudanian Savanna, making them a potential net positive for the region and the planet.
"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," study author Safa Motesharrei said in a University of Illinois press release published by ScienceDaily.
The researchers focused on the Sahara because it is an ideal location for such an ambitions renewable energy scheme.
"We chose it because it is the largest desert in the world; it is sparsely inhabited; it is highly sensitive to land changes; and it is in Africa and close to Europe and the Middle East, all of which have large and growing energy demands," lead author Yan Li said.
The study found that wind farms would increase rainfall because they would both increase temperature by drawing warm air down at night and decrease wind speed by creating more friction. This would lead to a doubling of rainfall where wind farms were installed.
The solar farms would increase rainfall by reducing albedo, the amount of light reflected by the land, which in turn would increase precipitation.
In both cases, researchers found that precipitation would increase vegetation, which would reduce albedo further, leading to more precipitation. The effect was increased if both solar and wind farms were installed.
Study author Daniel Kirk-Davidoff told AFP that the effect would not be that dramatic in the grand scheme of things—the desert would stay dry—but that the additional vegetation in the region's south would make an important difference for the people living there because it would increase grazing opportunities.
"It is hard to imagine that this would be a bad thing from the point of view of human communities there," he said.
While local temperature increases were part of the projected impact of the installations, the researchers made clear that those changes would stay in the Sahara and Sahel, not spread around the world like the global warming caused by greenhouse gasses, AFP reported.
One element that separated the study from previous research was its focus on vegetation, Li said in the University of Illinois press release, since most studies that have looked at the impact of solar or wind installations on climate have not also looked at how those climate changes would impact vegetation, or how the changed vegetation would then change the climate.
"Previous modeling studies have shown that large-scale wind and solar farms can produce significant climate change at continental scales," Li said. "But the lack of vegetation feedbacks could make the modeled climate impacts very different from their actual behavior."