Why can’t we just cover the Sahara with solar panels?

Gerhard Knies, a particle physicist, sat down one day and worked out that in just six hours, the world’s deserts receive more solar energy than the entire human race consumes in a year.

The energy needs of the world could be met by just covering 1.2 percent of the Sahara desert in solar panels.

So why haven’t we?

Some people have tried. The Desertec initiative planned to put solar panels in the Sahara that would power a great deal of the Middle East and Northern African energy needs while also sending 15 percent of Europe’s electricity requirements abroad. All for the low, low price of €400 billion. A number of industry partners lined up to take part but by 2014, of the seventeen initial partners, only three remained.

Things proved unfeasible quite quickly.

Using the desert’s energy supply isn’t a problem; but transporting it to where it’s needed is. Getting that electricity to where it needs to be requires power lines to get it to the closest power plant. Then you need to ping that electricity around the world to its buyer without losing any of it. Desertec’s plan was to use high-voltage DC power lines where the energy losses could be as little as 3 percent per 1,000 kilometres, which is much lower than the AC power lines we’re used to. But nothing on the scale needed had ever been built before: 30 GW of power would need to be transported from the Sahara to Europe (over 3,000 kilometres) and the longest link so far is a Chinese effort transporting 12 GW across 3,000km.

Maintenance of a solar farm is a hassle on a small scale. Dust and sand quickly accumulate on solar panels, reducing their efficiency, and while there’s research underway into self-cleaning, dust-repelling panels, for the moment, they simply get too dusty for optimal use. While you could argue keeping the panels clean would provide jobs, that’s one hell of an undertaking. Sand is the bane of every technology—even when it hasn’t (yet) found its way into every nook and cranny of a device, it literally carves the outside of anything it touches into oblivion. Besides, deserts are harsh environments. They’re not just hot—temperatures shift wildly between day and night, putting rapid thermal cycles on any solar panel materials.

The solar panels we have so far simply can’t handle that level of abuse regularly.

Even if they could, there’s the small issue that all renewable energies face: consistency. The Sahara desert is reliably hot and sunny, but only for 20 hours each day, assuming you had enough solar cells to meet global supply on both sides of the Sahara. That’s most of the day with energy production, but still four hours with nothing. There are few people who would be happy if their electricity was cut off for four hours each day.

Storing the energy produced isn’t much of a possibility yet either. Batteries are difficult and expensive to manufacture, require materials with increasing scarcity, produce a lot of pollution in manufacturing, and aren’t particularly durable. There are other methods of storage available such as pumped-storage hydroelectricity. Hydro. In the desert. Even if that were feasible, or the electricity were transported to somewhere it could be, current worldwide storage using this technique only accounts for less than 1 percent of all power used globally. There is the potential for a European ‘super-grid’ allowing for power transmission from regions of excess production to regions of excess need, thereby ensuring a constant supply of electricity, but you remain at mercy of the weather. As reliable as a hot sunny day in the Sahara is, there’s always the potential for an interruption in sunshine supply.

None of this even touches upon the political problems. A project like this would be long-term (Desertec didn’t expect to finish until 2050) meaning there’d be a lot of moving parts, involving several countries that could each see a changing political landscape interrupting or ending the entire project. Unfortunately, Africa is home to a few unstable governments of the variety that inspire caution in investors of multi-billion dollar projects. Libya’s civil spring certainly spooked some Desertec investors. There’s also the more delicate political issue of natural resource rights. Countries have been made rich through exports of coal or oil—wouldn’t a country with the keys to the world’s future energy supply want to benefit in the same way?

Finally, contrary to popular belief, deserts are not ‘useless land’—they’re incredibly complex and fragile ecosystems that play a vital part in the global environment. What could possibly go wrong if you interfere with that? For starters, that’s a lot of desert tortoises losing their homes.

The worst that could happen is changing the climate, for better or for worse. Among the many things that contribute to a local climate is albedo, the percentage of sunlight that reflects off the ground. The albedo determines how hot the ground gets and how much of that heat gets reflected back into the air, playing a huge role in determining local climate. Local climate, in turn, affects global climate.

Desert cities like Phoenix in Arizona discovered this the hard way. As they started paving over the desert with more and more concrete and asphalt, they discovered average local temperatures were rising worryingly quickly. Solar panels would work similarly, but wouldn’t just change the albedo, but also the dynamics of the ground heating and cooling, because now there’s a bunch of very hot panels with very shady areas underneath them.

So in addition to all the other problems involved in covering the desert with solar panels, there’s no telling what this kind of plan would do to the climate. What starts as a plan to tackle climate change could easily tip the wrong way: you might turn your nice sunny desert into a local version of Seattle; or you might turn Seattle all those miles away into a desert. ■

Sustainability

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