Wind, solar farms could increase rain, vegetation

A new study by University of Maryland scientists has conducted innovative experiments on climate and vegetation patterns to show that wind and solar farms could more than double rainfall in the Sahara and increase by about 20 inches ( 500 mm / year). in the Sahel, a semi-arid transition region south of the Sahara.

Large wind and solar farms in the Sahara could provide enough energy to replace fossil energy currently used and for the foreseeable future.

The main effect of these renewable energy operations would be a substantial reduction in greenhouse gas emissions of human origin and the resulting mitigation of climate change. However, such large-scale wind and solar farms could also affect the regional climate due to changes in the properties of the soil surface.

An international group of researchers, led by scientists from UMD, has explored these climate impacts by including two-way feedbacks of vegetation between a global climate model and a land / vegetation model.

Their conclusions have been published in Science.

"The results of our model show that the large solar and wind parks of the Sahara would more than double the rainfall in the Sahara and that the largest increase occurs in the Sahel, where the scale of the Sahara rainfall increase is between 200 and 500 mm each year, "said Yan Li, lead author of the journal and postdoctoral researcher at the UMD at the beginning of the study." As a result, the fraction of plant cover increases in size. 39, about 20%. "

"The increase in rainfall predicted by our model would result in substantial improvements in rainfed agriculture in the region, and the increase in vegetation would lead to an increase in production," said Safa Motesharrei, researcher at UMD Systems. "The Sahara, the Sahel and the Middle East include some of the driest regions in the world, while experiencing strong demographic and demographic growth.Our study has major implications for resolving sustainability issues inseparable from the Energy-Water-Link. Food in this region. " In addition, the availability of huge amounts of clean energy would allow the desalination of seawater and its delivery to the regions most affected by the severe shortage of fresh water, which would lead to an improvement in public health, an expansion of agriculture and food production. same restoration of biodiversity. "

"This study accomplishes something completely new: it shows how human action can affect the soil surface through the construction of solar and wind farms and shows that for a change of this magnitude, it is fundamental Paolo D & # 39; Odorico, professor of ecohydrology at the University of California, Berkeley, who was not co-author, said global climate models explained the land-atmosphere feedbacks.

Past prelude

"In 1975, Jule Charney, my MIT consultant, proposed a feedback mechanism to explain the drought in the Sahel, the semi-arid transition region south of the Sahara: overgrazing has increased surface albedo [reflectivity]by reducing rainfall and further reducing vegetation, "Eugenia Kalnay, prominent professor at the University of Maryland and lead author of the paper". About ten years ago, I had the idea that this feedback would work in the opposite direction in the presence of large solar panel farms, because it would reduce surface albedo. Similarly, wind farms would increase surface friction and air convergence, producing upward movement and precipitation. This is a second feedback mechanism that was discovered by Y.C. South in 1985, but still in the opposite direction. These feedback mechanisms suggest that large wind farms and large solar farms in the Sahara would significantly increase rainfall and vegetation. Our results support this conclusion. "

"Solar and wind energy projects in Africa and the Middle East are already underway, from Morocco to Dubai in Ethiopia, including more than 200 GW of solar energy by 2030", said Jorge Rivas, co-author and political scientist. "This renewable electricity could be transported to areas a few thousand kilometers away, and long-distance transmission lines already exist in Africa and elsewhere for decades."

This study shows that "the dynamic return of vegetation could improve the impact of land-use changes on climate in this specific region. [Sahara and Sahel]Guiling Wang, professor of hydroclimatology at the University of Connecticut, said: "Studies using static models [prescribed] vegetation may underestimate the effects on regional climate of human activities such as deforestation or wind and solar farms. "

"These experiments with dynamic vegetation feedback in our model show that the positive return of rainfall-vegetation-albedo accounts for about 80% of the simulated increase in rainfall in wind farm experiments," Eviatar Bach, Ph. D. The candidate for the Department of Atmospheric and Oceanic Sciences (AOSC) and co-author of the UMD said.

The dynamic vegetation model was developed by Ning Zeng, co-author and professor at UMD AOSC, and coupled with the global climate model developed by Fred Kucharski, co-author and climatologist at the International Center for Theoretical Physics in Italy.

"Although surface roughness and albedo may affect climate and rainfall, the finding that the introduction of dynamic vegetation would lead to a strong positive feedback of precipitation is new," said J. Shukla, George Mason University, said. "This research certainly suggests that it will be possible to create an autonomous renewable energy system, which will be very beneficial for the socio-economic development of the region."

"The Sahara has been developing for a few decades and solar and wind farms could help stop the expansion of this arid region," said Russ Dickerson, leader of air quality research and professor at the AMD AOSC. "It sounds like a win-win for me."