Such sentiments propose another challenge for DESERTEC: How will it guarantee that the electricity Europe needs is sent down the transmission cables and not just all consumed locally? And how will MENA countries justify selling the electricity to Europe — where the retail price of electricity can be up to 20 times more expensive — if the local population is, say, experiencing regular blackouts?
At the visitor center at Kuraymat, bottles of chilled water are being distributed ahead of a tour of the parabolic troughs. The mid-morning November sun is already heating the engine oil-like fluid inside the troughs’ receiver tubes — a technology not that far removed from Shuman’s century-old design — up toward 400?C.
The technical questions are coming thick and fast for Bodo Becker, the operations manager at Flagsol, a German company that specializes in building concentrated solar power (CSP) plants in the deserts of the US, Spain and now Egypt. The leading query is how the troughs perform in such harsh conditions.
“We only have one sandstorm, on average, pass through here each year,” he says, “but we tilt the troughs down and away from the wind whenever it gets up beyond 12 meters per second, as they act like giant sails.”
Keeping them clean is the main challenge, he adds.
“Due to the dusty conditions, we are witnessing about 2 percent degradation every day in performance, so we need to clean them daily. We use about 39 cubic meters of demineralized water each day for cleaning across the whole site.”
This surprises many delegates, as they have previously been told at the conference that CSP troughs need cleaning weekly compared to photovoltaic panels which need cleaning monthly. Either way, it highlights yet another challenge for DESERTEC: Can enough local water ever be secured for cleaning duties?
The Nile is just a few miles from Kuraymat, but some countries aim to push much deeper into their deserts to build such facilities. “Dry cleaning” technologies are being developed, but they reduce the generating efficiency at the plant. Either way, the super-heated transfer fluid requires cooling before it can loop back to the troughs for re-use, and, as with cleaning, water is the cheapest and easiest way to do this. Until “dry cooling” technologies are further advanced, it could limit solar farms to the desert fringes close to large bodies of water.
Somewhat counter-intuitively, some countries, such as Jordan, now favor wind over solar as a source of desert energy, because it is currently more affordable and isn’t so water-intensive. But it is suspected that it will be many years before a single desert energy technology comes to dominate the market. Some within the industry advocate photovoltaic panels, but, currently, CSP is more popular.
However, even within CSP, there are loyalists for parabolic troughs and others for “solar towers,” which rely on hundreds of pivoting mirrors laid out on the ground to track the sun and direct its rays toward one fixed point at the top of a giant tower.