Wind and Solar Farms Could Bring the Rains Down in Africa

Stretching over 3.55 million square miles, the Sahara desert sees its fair share of sun. But apart from scoring you a serious sunburn, these energetic waves stand to make a big impact on the future of humankind. Last week in Science, researchers proposed that speckling the sands of the world’s largest hot desert with solar panels and windmills could meet the entire world’s energy needs several times over—and bring some much-needed rainfall to these arid skies.

The Sahara isn’t entirely without pockets of lush vegetation. In bushier areas of the desert, dark vegetation acts as a cloak, absorbing sunlight and warming the ground, whereas the vast areas of pale sand reflect the sun’s rays, leaving the ground relatively cooler. Balmy soil then drives hot air upwards, wringing moisture out of the atmosphere as it condenses and falls back to the earth as rain.

But such oases are few and far between, and the desert is actually expanding. In the last century alone, the Sahara became about 10 percent larger. As the desert grows, barrenness begets barrenness. With plant life decimated, the dirt cools, sapping the driving force for precipitation and with it, the chance for life to arise from the parched sands.

In the face of this vicious cycle, however, researchers are getting creative. “It occurred to me that the same [cycle could] go in the opposite way, so it would increase precipitation, and vegetation, and then more precipitation,” Eugenia Kalnay, one of the study’s authors, explained to Dan Charles at NPR.

One way this could happen is by covering 20 percent of the Sahara with solar panels, which would convert the sun’s rays into energy while absorbing sunlight just like vegetation would. The toasty earth would then be poised to push warm air skyward, thus encouraging rainfall—eventually coaxing vegetation back from decimation.

Alternatively, scientists could deploy an arsenal of wind farms. Spinning turbines would generate power as well, but this many wind farms concentrated in one area would also collectively slow local wind speeds and push masses of warm and cool air together. Combined, the reduced wind speeds and turbulence would buoy air masses upwards, encouraging the formation of rain clouds.

The solar panels and wind turbines would serve primarily as a temporary boost as vegetation recovered, the researchers say. In the model, the reintroduction of plants to some parts of the region would account for about 80 percent of the increase in rainfall in years to come.

A group of researchers led by Kalnay and her colleague Yan Li modeled these scenarios to study their effects, as well as a third that combined solar and wind energy, generating 82 terawatts of electrical power—over four times our total global energy use.

In the researchers’ model, the solar panels bested the wind farms in terms of energy production, but the turbines produced the larger climate impact, roughly doubling predicted precipitation. Together, the technologies increased rainfall by about 150 percent.

Still, the Sahara is unlikely to ever transform into a tropical rainforest. And for now, the researchers’ solar panels and wind farms remain confined to a computer simulation. If a project even a fraction of this size were ever to be undertaken, immense coordination would be necessary, taking into account not only the logistics of engineering, but also monetary funds, governmental cooperation and cultural awareness for the locals this technology would most impact.

Notably, the addition of solar panels and wind farms would also increase the average temperature in the region by about 5 degrees Fahrenheit. Additionally—with a dash of irony—the models works best with less efficient solar panels. As technology accelerates, solar panels that are better at converting energy would also rob the ground of the warm air needed to produce rainfall, and even decrease local precipitation.

“In terms of willingness, yes, people are certainly willing and able to construct dozens of energy plants in the deserts and semi-deserts of Africa,” David Wright, an archeologist at Seoul National University who was not involved in the study, told Mary Beth Griggs at Popular Science. “Whether it is prudent to do so is an open question… there are more costs to such projects than just ecological.”

Still, the potential impact of sustainable energy farms could be massive, and currently, there isn’t much competition for Saharan real estate.

Katherine J. Wu | | READ MORE

Katherine J. Wu is a Boston-based science journalist and Story Collider senior producer whose work has appeared in National Geographic, Undark magazine, Popular Science and more. She holds a Ph.D. in Microbiology and Immunobiology from Harvard University, and was Smithsonian magazine's 2018 AAAS Mass Media Fellow.