Large-scale wind and solar energy "could make the Sahara greener"

The installation of a large number of solar panels and wind turbines in the Sahara Desert would have a major impact on rainfall, vegetation and temperatures, according to the researchers.

They found that the actions of the wind turbines would double the amount of rain that would fall in the region.

Solar panels have a similar impact, but they act differently.

The authors claim that their work reinforces the view that large-scale renewable energies could transform the Sahara region.

Scientists have modeled what would happen if 9 million square kilometers of the Sahara Desert were covered by renewable energy sources.

They have focused on this sector because they are sparsely populated and are also exposed to significant amounts of sun and wind and are close to major energy markets in Europe and the Middle East.

According to the authors' calculations, a massive installation in the desert would generate more than four times the amount of energy that the world currently uses each year.

Previous studies have shown that the installation of wind and solar energy can have an impact on temperatures, but the main difference with this research is the impact on vegetation.

"The results of our model show that the large solar and wind power plants in the Sahara would more than double the rainfall, especially in the Sahel, where the magnitude of rainfall increase is between 20 and 500 mm per year," he said. said Dr. Yan Li. author of the article from the University of Illinois, USA.

"As a result, the plant cover fraction increases by about 20%."

According to the study, in the Sahel, semi-arid region south of the Sahara, average rainfall increased by 1.12 mm per day.

How do turbines and panels increase precipitation?

With wind turbines, it is all about mixing air caused by the rotation of the blades. Wind farms mix the warmer air coming from above, which creates a feedback loop in which more evaporation, rainfall and plant growth occur.

"Wind farms increase the roughness of the surface and therefore increase wind convergence in low pressure areas," said Dr. Li. "Convergent air must increase, cool and moisture condense, which will lead to increased precipitation. "

Solar panels actually reduce the reflection of sunlight from the surface known as the albedo effect. This triggers a positive albedo-rainfall-vegetation return that results in rainfall increases of about 50%, report the authors.

"The panels directly reduce the surface albedo, resulting in greater absorption of solar energy and surface warming, which reinforces the Saharan heat, resulting in increased air and precipitation," explains Dr. Li.

What would be the impact on people?

Mostly positive, say the authors.

"The increase in precipitation predicted by our model would result in substantial improvements in rainfed agriculture in the region, and the increase in vegetation would result in an increase in livestock production," said Dr. Safa Motesharrei from the University of Maryland. paper.

"The Sahara, the Sahel and the Middle East include some of the driest regions in the world, while experiencing strong demographic and demographic growth, and our study has major implications for addressing the inseparable challenges of energy continuity in this region. . "

But temperature increases are bad for climate change, right?

The authors state that the thermal impact of all these turbines and panels would not make any significant difference.

"Local warming by wind turbines and solar farms is much lower compared to future warming reduced greenhouse gases that renewable energy on this scale would imply," said Dr. Li.

Will it work with smaller scale renewable facilities?

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

"In general, the climate impacts are reduced with reduced facilities, but this result also depends very much on the exact locations," said Dr. Li.

"High-resolution modeling may be needed to better study the more regional impacts of wind and solar farms."

Should we now proceed to large installations in desert areas?

"Yes, I think so," said Dr. Li.

"The main message for people, decision-makers and investors lies in the huge benefits to the people, society and ecosystems resulting from these solar and wind farms."

"We hope that, in the light of our discoveries and the fact that the primary climate effect of these farms, the reduction of anthropogenic greenhouse gas emissions and the consequent mitigation of climate change, we will be able to transform our sources of energy to support fresh water, food and life on our planet. "

The study was published in the journal Science.