By Irina Slav
Two years ago, a team of Finnish scientists estimated that the world needs to get 69 percent of its primary energy from solar farms in order to achieve its ambitious net-zero goal.
That, the scientists said, would necessitate the construction of many more solar farms than are currently planned. And consensus has it that the Sahara would be the perfect place for a few giant solar farms. However, the consensus appears to be wrong, according to two researchers.
Zhengyao Lu from Sweden’s Lund University and Benjamin Smith from Western Sydney University warned in a recent paper that turning the Sahara into a giant solar farm will have negative consequences for the global climate because of the way solar panels work.
Everyone knows the basics: photovoltaic panels absorb the energy of the sun. But just a step beyond these basics, we are reminded of the efficiency factor of solar panels, or the rate, at which it converts the energy it absorbs into electricity. The average to date is between 15 and 20 percent. So, 15-20 percent of the light solar panels absorb, they convert into electricity. The rest appears to be the problem, according to Lu and Smith.
The energy that solar panels cannot convert into electricity gets released back into the environment in the form of heat, the climate researchers explain. And because solar panels are darker than sand, they absorb—and therefore release—a lot more heat than sand in the Sahara does, because sand is a lot more reflective than solar panels.
This returned heat would create a much sharper difference between the Sahara and the oceans around it. This difference, Lu and Smith explain, will bring more rain to the Sahara as it reduces the surface pressure of the air and boosts the rate of moist air rising and condensing. More rain will ultimately turn the Sahara into a lush green area once again. But that’s not the boon it may sound like.
Any tampering with the Earth’s climate patterns, however good the intentions, tends to have destructive consequences. Turning the Sahara into a solar hub, even with just 20 percent of its surface covered with solar panels, will also end up having adverse effects on the global climate, according to the two researchers.
The thing to bear in mind is that everything in nature is interconnected, and this is as true of ecosystems as it is of climate patterns. Saharan sand, carried on wind streams, for example, brings nutrients to the Amazon and the Atlantic Ocean. Even more importantly, the excessive heat generated in the desert by solar panels will change air flows and ocean circulation, according to Lu and Smith, which will, in turn, affect rain patterns.
Ultimately, the research suggests that covering even a fifth of the Sahara with solar panels will result in higher global temperatures, albeit the increase will be below 1 percent if that’s any consolation. Yet it will be unevenly distributed, Lu and Smith note, with polar regions affected more than tropical regions, exposing more sea as the ice melts, and attracting more heat as water is darker than ice and absorbs more water. In the end, the effects begin to sound like a vicious circle.
The study, which used computer modeling for its conclusions, should be a wake-up call for the most radical part of the renewable energy lobby that continues to argue that covering the earth with solar panels will save it. The truth is that human activity, whatever it is, invariably affects natural processes and patterns, and this effect is rarely positive.
Turning the Sahara into a giant solar farm sounds like it makes perfect sense only on the face of it. We might be much better off with agrivoltaics: combining farming and solar power to the benefit of all involved, with solar having a much lower if any, environmental footprint than it would in the Sahara.