Solar panels all over the Sahara desert?

You may have seen a variant of this meme before. A map of North Africa is shown, with a surprisingly small box somewhere in Libya or Algeria shaded in. An area of the Sahara this size, the caption will say, could power the entire world through solar energy:

Area of Sahara you’d need to cover with solar panels to supply the world’s electricity via @IFLScience pic.twitter.com/029gEJ4WT8

— Martin Varsavsky (@martinvars) April 20, 2015

Over the years various different schemes have been proposed for making this idea a reality. Though a company called Desertec caused a splash with some bold ideas a decade ago, it collapsed in 2014 and none of the other proposals to export serious amounts of electricity from the Sahara to Europe and beyond are anywhere close to being realised.

It’s still hard to store and transport that much electricity from such a remote place, for one thing, while those people who do live in the Sahara may object to their homeland being transformed into a solar superpower. In any case, turning one particular region into a global energy hub risks all sorts of geopolitical problems.

The Imagine newsletter aims to tackle these big “what if” questions, so we asked a number of academics to weigh in on the challenges of exploiting the cheapest form of electricity from perhaps the cheapest and best spot on Earth.

Sahara has huge energy potential

He points to the sheer size and amount of sunshine the Sahara desert receives:

• It’s larger than Brazil and slightly smaller than the US.
• If every drop of sunshine that hits the Sahara was converted into energy, the desert would produce enough electricity over any given period to power Europe 7,000 times over.

So even a small chunk of the desert could indeed power much of the world, in theory. But how would this be achieved?

Al-Habaibeh points to two main technologies. Both have their pros and cons.

• Concentrated solar power uses lenses or mirrors to focus the sun’s energy in one spot, which becomes incredibly hot. This heat then generates electricity through a steam turbine.
• In this image the tower in the middle is the “receiver” which then feeds heat to a generator:

• Some systems store the heat in the form of molten salt. This means they can release energy overnight, when the sun isn’t shining, providing a 24h supply of electricity.
• Concentrated solar power is very efficient in hot, dry environments, but steam generators use lots of water.
• Then there are regular photovoltaic solar panels. These are much more flexible and easier to set up, but less efficient in the very hottest weather.

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