Solar, Wind Power Create Hotter, Greener Deserts
By Sunny Lewis
CHAMPAIGN, Illinois, September 6, 2018 (Maximpact.com News) – Wind and solar farms are known to have local effects on heat and humidity in the regions where 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. Overall, the researchers report, the effects would likely benefit the region.
The study, “Climate model shows large-scale wind and solar farms in the Sahara increase rain and vegetation,” reported in the journal Science, 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.
Lead author Yan Li, a postdoctoral researcher in natural resources and environmental sciences at the University of Illinois, 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 new study, co-led with Eugenia Kalnay and Safa Motesharrei at the University of Maryland, focused on the Sahara for several reasons, Li said.
“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,” he said.
The Sahara is the largest hot desert and the third largest desert in the world after Antarctica and the Arctic. Its area of 9,200,000 square kilometres (3,600,000 sq mi) is comparable to the area of China or the United States.
The Berber people occupy much of the Sahara, and Tuareg nomads continue to inhabit and move across wide stretches of the Sahara today.
The wind and solar farms simulated in the study would cover more than nine million square kilometers and generate, on average, about three 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,” 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 authors wrote.
Precipitation also increased as much as 0.25 millimeters per day on average in regions with wind farm installations.
“This was a doubling of precipitation over that seen in the control experiments,” Li said.
In the Sahel, average rainfall increased 1.12 millimeters per day where wind farms were present.
“This increase in precipitation, in turn, leads to an increase in vegetation cover, creating a positive feedback loop,” Li said.
Solar farms had a similar positive effect on temperature and precipitation, the team found. 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,” Kalnay said. “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.”
And the development of solar power in the northern Sahara Desert has already begun on the dunes below Morocco’s sun-scorched High Atlas mountains.
Thousands of curved mirrors, each taller than a human, stand in rows as part of the Noor solar-power generating plant that is changing how the African continent produces its electricity.
The mirrors cover an area of roughly 1.4 million square metres. The first phase of this plant, which came online in 2016, generated enough electricity to supply 650,000 people.
By 2020, or possibly sooner, the US$9 billion solar power plant is expected to generate 580 megawatts (MW), enough electricity to power over a million homes.
It’s a game-changer for Morocco, a country that until recently imported 97 percent of its energy. In the near future, Morocco aims to become an exporter of power supplies to Europe, elsewhere on the African continent and the wider Arab-speaking world.
And the environmental effects of the solar installation are likely to benefit the region where it is located.
“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,” Motesharrei said.
That help is much needed. According to a study published in March in the “Journal of Climate,” the Sahara Desert has grown by roughly 10 percent over the past century.
A research team from the University of Maryland analyzed data collected since 1923 and concluded that while the greatest causal factor of the growth of the desert that is roughly the size of the United States is due to naturally-occurring changes, a third of the expansion can be linked directly to climate change.
The expansion is not good news, particularly for inhabitants of the neighboring Sahel border region, as the increased heat changes fertile farmlands to dry, barren land.
This is the first study to take a century-long look at the world’s largest desert. The authors suggest other deserts may be expanding as well because of global warming.
“Our results are specific to the Sahara, but they likely have implications for the world’s other deserts,” Sumant Nigam, senior author of the study and professor of atmospheric and oceanic sciences at University of Maryland, said in a statement.
The Sahara Desert expanded over the 20th century, by 11 percent to 18 percent depending on the season, and by 10 percent when defined using annual rainfall.
The desert expanded southward in summer, reflecting retreat of the northern edge of the Sahel rainfall belt, and to the north in winter, indicating potential impact of the widening of the tropics.
The evaluation shows that modeling regional hydroclimate change over the African continent remains challenging, warranting caution in the development of adaptation and mitigation strategies.
The study points to far-reaching implications for the future of the Sahara and other subtropical deserts like it. With inadequate rainfall to support crops, there will be “devastating consequences” for the world’s growing population, the scientists said.
Natalie Thomas, a graduate student in atmospheric and oceanic science at University of Maryland and lead author of the research paper, said the next step for the team is to look at the rainfall and temperature trends that are driving the expansion of the Sahara and other deserts.
“The trends in Africa of hot summers getting hotter and rainy seasons drying out are linked with factors that include increasing greenhouse gases and aerosols in the atmosphere,” said Ming Cai, a program director in the National Science Foundation’s Division of Atmospheric and Geospace Sciences, which funded the research on the Sahara Desert. “These trends also have a devastating effect on the lives of African people, who depend on agriculture-based economies.”
Featured Images: A traveler walks the Erg Chebbi dunes at sunset in Morocco’s part of the Sahara Desert. October 8, 2017 (Photo by Brian Geltner) Creative Commons license via Flickr