More than just clean energy: wind and solar in the Sahara could increase rainfall in the Sahel

Peter Thoeny/Visualhunt

 

New research indicates that large-scale wind and solar farms in the Sahara Desert could not only provide the world with all the energy it needs but also boost vegetation and improve livelihoods in adjacent drylands.

The idea of covering the entire Sahara Desert with a combination of solar and wind farms is not new, but it’s attractive: theoretically, you could supply enough green energy to easily meet current global electricity demand.

However, a new study indicates that such an installation could also increase rainfall and vegetation, creating a feedback loop which further greens the environment both of the Sahara and the adjacent Sahel, an impoverished dryland running from Senegal to Djibouti.

Modelling done by the study indicates that huge numbers of wind turbines and solar panels in the Sahara could lead to a local temperature increase and more than a twofold precipitation increase, especially in the Sahel, through increased surface friction and reduced albedo (the proportion of the incident light or radiation that is reflected by a surface): solar panels reflect less sunlight than Saharan sand, thus warming the land.  

Increases in vegetation further reduce surface albedo. Additionally, vegetation increases evaporation, surface friction, cloud cover, and consequently, precipitation. In previous studies, vegetation feedback has been overlooked.

Wind farms at scale also create more rainfall. Their blades “cause significant regional warming on near-surface air temperature… with greater changes in minimum temperature than maximum temperature,” says the study. “The greater night-time warming takes place because wind turbines can enhance the vertical mixing and bring down warmer air from above to the lower levels, especially during stable nights.”

The region most likely to benefit from such an installation, says the study, is the Sahel. “The most substantial precipitation increase occurs in the Sahel, with a magnitude of change between +200 to +500 mm/year, which is large enough to have major ecological, environmental and societal impacts,” says the study.

Solar farm in Morocco. Photo by Mohamed Atani/UN Environment

“Massive investment in solar and wind generation [in the Sahara Desert] could promote economic development in the Sahel, one of the poorest regions in the world, as well as provide clean energy for desalination and provision of water for cities and food production,” the study adds.

The “Yes buts…”
The biggest obstacle to any large-scale renewables plan for the Sahara is political. There would have to be political buy-in from all parties concerned, including groups currently branded as terrorists.
Other issues that would also need careful consideration include the risk of sandstorms which could damage installations or impair their efficiency.

Maintenance of such a vast solar/wind system could be a huge challenge, and very costly if roads were to be built in the desert. How would you replace perhaps hundreds of faulty solar panels every day? Maybe teams using camels could be deployed? Perhaps new designs for solar panels would be needed to make them more biodegradable (panels are currently made of aluminium, which is very energy intensive to manufacture). 

On the plus side, perhaps solar panels could be designed to gather a teaspoonful of water condensation per panel. Nothing is impossible if the political will is there.

“With the world still set to fall well short of meeting even the most modest climate change targets as set out in the Paris Agreement, ambitious goals backed by rigorous science and international political will are the best hope of preventing us reaching a climate change tipping point where whatever we do will be too little, too late,” says Niklas Hagelberg, a UN Environment climate change specialist.

UN Environment is due to publish its latest Emissions Gap Report in November.
For further information, please contact Niklas Hagelberg