Topaz solar farm in California. (Image Credit: NASA Landsat)


Is nothing in power generation good for the environment?


Some deserts in the world could have one key advantage: harvesting solar energy. Deserts are massive, silicon abundant, flat, and full of sunlight. Ten of the world’s largest solar plants are found in deserts or dry regions. However, some issues need to be considered.


The solar panels’ black surface absorbs most of the sunlight, but only 15% is converted into electricity, with the remaining discharged into the environment as heat. Ultimately, this causes a problem for the climate. The heat released from thousands of square kilometers of solar plants would be re-distributed by the atmosphere’s airflow, impacting regional and global effects on the climate.


A climate model was used in a 2018 study to stimulate lower albedo effects on desert land surfaces resulting from huge solar farm installations. It showed that a feedback loop is triggered when the solar farm takes up 20% of the Sahara’s total area. The heat emitted from the darker solar panels causes an abrupt temperature difference between the land and surrounding oceans that reduces surface air pressure and causes condensation. More monsoons meant that plants would grow, causing the desert to reflect less solar energy because vegetation absorbs more light than soil and sand. More plants increase evaporation, leading to a humid environment causing vegetation to expand.


Other studies indicate that an identical feedback loop caused the Sahara to flourish with greenery during the African Humid Period.


Recently, another study was conducted using an advanced Earth system model to observe the interactions between Saharan solar farms and the climate.  The model takes these complex feedbacks into account: the atmosphere, ocean, land, and its ecosystems. It revealed that remote areas of the land and ocean could be unintentionally affected.

The model also showed that installing solar farms on 20% of the Sahara increases local temperatures by 1.5°C. With 50% covered, that temperature increase is 2.5°C.  Eventually, the atmosphere and ocean movement could spread warming around the world. The Earth’s average temperature increases by 0.16°C at 20% coverage and 0.39°C at 50% coverage. This also has a devastating effect on the polar regions since more sea ice would be lost in the Arctic. As a result, warming is accelerated largely because melting sea ice uncovers dark water that absorbs more solar energy.


Worldwide precipitation patterns would also be affected as a result of the revamped global air and ocean circulation. In the simulations, heavy rainfall in the tropics moves northward, causing droughts in the Amazon region due to less moisture from the ocean. Even more alarming, the model suggests that frequent tropical cyclones would target North American and East Asian coasts. 


However, the model doesn’t include some important processes like dust blown from large deserts. Saharan dust provides the Amazon and the Atlantic Ocean with nutrients. A  greener Sahara would make a bigger impact on the world than the simulations predicted.


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