For obvious reasons, deserts are among the best places to deploy solar panels on mass scale, as indicated by the fact that – at the time of this writing – the ten largest solar plants around the world are located in deserts or dry regions.
In recent past, researchers have devised plans for converting the Sahara Desert into a massive solar farm that could meet the world’s current energy demands four times over. Already, blueprints have been made for projects in Tunisia and Morocco.
Back in 2018, a study by an international team of researchers has shown that covering roughly 20% of Sahara in solar panels might kick-start a process that could result in something akin to the African Humid Period when the Desert was green.
More work is needed to figure out how to mass-deploy solar panels in deserts without causing unintended negative consequences. Image: James Moran via flickr.com, CC BY-NC 2.0
This could happen through a feedback loop triggered by a temperature difference between the land and the surrounding oceans, itself caused by the heat reflected off the solar panels, which are darker than sand.
The temperature differential would reduce surface air pressure, leading to the condensation of moist air and, eventually, monsoon rainfall. As vegetation spreads by soaking up the rainwater, the amount of heat emitted by the desert would go down because plants absorb light better than sand and soil.
Sounds great, right? Transforming an arid desert into a lush oasis, while meeting the world’s energy needs at the same time. Unfortunately, even if such a project is viable, more work is still required to address some of the potential downsides.
A study that was recently published in the journal Geophysical Research Letters used an advanced Earth systems model, which takes into account the various feedbacks between interacting spheres of the world’s climate, and reached some disconcerting results.
Covering 20% or 50% of Sahara with solar panels would increase local temperatures by 1.5°C or 2.5°C, respectively. The atmosphere and ocean movement would then spread the heat around the world, causing an average rise in global temperature by 0.16°C or 0.39°C, with some of the most significant warming taking place in polar regions.
The shifting global air and ocean circulation would cause droughts in the Amazon and more frequent tropical cyclones in North America and East Asian coastal regions. Since the model does not include the movement of dust – a vital source of nutrients for the Amazon – a green Sahara could also have other unforeseen effects downstream.
Given these considerations, in an article for The Conversation co-authors Zhengyao Lu and Benjamin Smith emphasise that while “solutions like this may help society transition from fossil energy, but Earth system studies like ours underscore the importance of considering the numerous coupled responses of the atmosphere, oceans, and land surface when examining their benefits and risks”.