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| Fig. 1: Deserts such as the Sahara (pictured above) hold vast potential for wind and solar energy production. (Source: Wikimedia Commons) |
Wind and solar power can influence climate change by reducing humanity's dependence on fossil fuels which trap heat. Deployed en masse, wind turbines and solar cells can affect the climate of their surrounding environment in other ways. [1]
Deserts such as the Sahara Desert in Africa (Fig. 1) present interesting locations for wind and solar farms for several reasons: (1) land is inexpensive, (2) wind and sun are abundant, and (3) their remoteness would preclude interference with human activity. The Sahara is especially interesting because it is so large that any cloudy weather would be localized, making energy availability highly reliable. [2] Researchers from the University of Maryland's Department of Atmospheric and Oceanic Science have estimated that covering the Sahara and the Sahel, a semi-arid region immediately south of the Sahara, with wind and solar production plants could meet the energy needs of the entire world four times over. [3]
These researchers investigated the potential effects of covering the Sahara and the Sahel with wind and solar production plants by conceptualizing three scenarios: (a) large-scale wind farming, (b) large-scale solar farming, and (c) large-scale wind farming and solar farming. Then they inputted these specifications into a computational model which simulates the Earth's dynamic climate. [4]
In scenario (a), the desert is dotted with 300-foot-tall wind turbines. [1] The giant turbines would cause warm air above to mix with cooler air below. Near the ground, air temperatures would go up about four degrees Fahrenheit. The presence of the turbines interrupting the desert's smooth surface would also cause winds to move more slowly through the area. These changes would be enough to bring more moisture to the region and double the local rainfall, increasing it by up to 0.25 millimeters per day. Plant growth would increase as a result, and those dark, leafy plants would reduce surface albedo, the reflectivity of the desert's surface. [4] The phenomenon wherein plant growth reduces surface albedo is already on display in the Sahara's sparse oases. [2]
In scenario (b), the researchers specified that solar panels would cover 20% of all land in the region. [1] The main effect would be the reduction of albedo, increasing precipitation by about 0.13 millimeters per day in the Sahara and 0.59 millimeters per day in the Sahel. This increased precipitation would further reduce albedo by inducing plant growth. [4]
In scenario (c), wind and solar farms would combine to produce about 82 terrawatts of electrical power, and average daily precipitation would increase to 0.59 millimeters. [1] This precipitation would not be spread evenly everywhere, and some parts of the Sahel could get up to 20 extra inches of precipitation each year. [4]
These three theoretical scenarios all lead to considerable environmental and ecological changes. It has been proposed that among these changes might be the slowing, halting, or even reversal of the Sahara Desert's gradual expansion, which previously seemed unstoppable. [3]
Independent scientists and politicians have weighed in on the feasibility of mass wind and solar farms across the Sahara. The co-founder of the Trans-Mediterranean Renewable Energy Cooperation (TREC), a network of experts on sustainable energy, has argued that this idea is both scientifically and economically sound. The professor of climate policy at ETH Zurich who leads the investigation for the European Research Council on whether Europe could rely on the Saharan sun for power cautions that international political battles will be fought to decide who will pay for the infrastructure, where it will be built, and how the energy would be distributed. The chemist and World Bank evaluator who founded the African Network for Solar Energy (ANSOLE) has stipulated that this endeavor would only be ethical if Africans share in the benefits. [2]
These environmental changes might not happen everywhere wind and solar farms are installed. In the Sahara and the Sahel, the surface albedo increasement phenomenon is key and might be different if the landscape were different. [1] However, any major development project -- even one with an environmentally conscious objective -- can have surprising impacts on the surrounding environment. Whether positive or negative, these potential impacts should be carefully considered and brought to the attention of local communities who would be affected.
© Jenny Vo-Phamhi. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] K. Kaplan, "Wind and Solar Farms Can Make Their Own Weather, Including Extra Rain Over the Sahara," Los Angeles Times, 6 Sep 18.
[2] G. Knies, "Should We Solar Panel the Sahara Desert?" BBC News, 30 Dec 15.
[3] D. Charles, "A Scientist Dreams Up a Plan To Stop the Sahara From Expanding," NPR, 9 Sep 18.
[4] Y. Li et al., "Climate Model Shows Large-Scale Wind and Solar Farms in the Sahara Increase Rain and Vegetation," Science 361, 1019 (2018).
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