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You already know that the use of solar and wind energy can influence the climate by reducing our dependence on fossil fuels. Now, scientists say that these forms of renewable energy can change the climate more directly – and do it in a way that might surprise you.
If wind turbines and solar panels were deployed across the Sahara, it would rain more and more plants would grow in the vast African desert, according to a study published in the Friday edition of the journal Science.
"Renewable energy can have multiple benefits for climate and sustainable development," wrote a team led by researchers from the Department of Atmospheric and Oceanic Sciences at the University of Maryland.
To achieve this, the researchers have devised three scenarios for the Sahara and the Sahel, a semi-arid region located immediately to the south.
In one of them, the area is dotted with wind turbines more than 300 feet high. In another, solar panels cover 20% of the land. The third case combines wind and solar farms – a facility that would produce about 82 terawatts of electricity a year. (For comparison, the world used about 18 terawatts of electricity in 2017, according to co-head of the study, Yan Li.)
Once their hypothetical energy farms were built, the researchers integrated these details into a sophisticated computer program that simulates the Earth's dynamic climate. Then the program made predictions about how farms would change the environment.
In the case of wind farms, giant turbines would result in a mixture of warmer air overhead with colder air, bringing more heat near the surface. Air temperatures near the ground would increase by almost 4 degrees Fahrenheit.
In addition, the turbines would interrupt the fluidity of the desert surface. The winds blowing in the region move more slowly.
This, combined with the extra heat, would change the weather conditions in the Sahara and bring more moisture to the area. According to the study, average rainfall would increase up to 0.25 millimeters a day, about double what it would have been otherwise.
Extra water would feed plant growth and these extra plants would reduce the amount of sunlight reflected from the desert surface.
From there, the researchers explained that the feedback loop (or surface albedo) decreased precipitation, which feeds plant growth, reducing albedo, and so on.
The story is a bit different for solar farms.
Instead of slowing the wind or causing the mixture of hot and cold air, the main effect of the solar panels is to reduce the albedo. This would increase average daily rainfall by about 0.13 millimeters in the Sahara and 0.59 millimeters in the Sahel. The extra water would induce greater plant growth, further reducing the albedo and allowing the cycle to continue.
These changes have been predicted to increase the maximum temperature by more than 2 degrees Fahrenheit, the researchers reported.
If the wind and solar farms were combined, these effects would be "improved," they said. Average daily precipitation would increase to 0.59 millimeters. It is nearly 1.5 times more than the Sahara would be in its natural state.
But the rain would not be evenly distributed everywhere. Computer simulations predicted that parts of the Sahel could reach nearly 20 inches of additional rainfall per year. All this extra water could have "major ecological, environmental and societal impacts," wrote Li and his colleagues.
The average temperature would also increase by almost 5 degrees Fahrenheit.
Changes such as these would not necessarily occur everywhere solar farms are built, the researchers warned. In the Sahara, the bottom line is that today's typical solar panels would increase surface albedo. But if the landscape was different, it might not be true.
Ditto if solar panels were more efficient – it could lower temperatures instead of rising. Without additional heat, precipitation would not increase. It could even decrease, the researchers noted.
These are all factors to consider when building a wind or solar farm, they wrote. If they are well placed, these plants could generate more rain and plants in addition to a cleaner energy.
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