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Should We Fill the Sahara With Solar Panels? (bbc.com)
An anonymous reader writes: A panel of experts at the BBC discuss the possibility of re-purposing the Sahara Desert. Instead of having over 9 million square kilometers of barren sand, we could start a massive project to gradually fill it with solar panels. The remarks are illuminating: "The technology is good. It's matured a lot in the last few years in terms of thermal storage. And the Sahara desert is so big that if there is cloudy weather, it's localized, and with thermal storage, it can provide absolutely reliable power." The difficulties turn out to be mostly political: "The biggest potential pitfall is that it's politically complicated. You're not going to develop solar energy in the Sahara unless you have a very strong state involvement, both on the side of the consumers and the project developers." And one of the panelists points out that Africa must have a large share of the benefits: "Things have changed. Africans are self-confident now, they want to participate in their development, and they want to have part of their resources, they are not just there to always give to the rest of the world and remain poor."
One big disadvantage of solar power is that it only works some of the time. The intermittent nature of both solar and wind is a serious problem. There's some amount that they help each other out, because in many locations the wind is strongest at night. Because of the intermittent nature of solar power, one cannot have large scale grids be completely solar without a lot of improvements in storage technology. Right now, battery technology is improving but it isn't where it needs to be. The best storage for most purposes right now is pumped hydroelectric https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity where one pumps water high up to a reserve when there is excess and then recovers it using a hydroelectric plant. This is more efficient than batteries. However, it requires specific geology to work well.
The other big issue with this plan is an issue is efficient transmission. If you are putting a large fraction of the entire world's power in one area, you are going to need to have massive transmission lines. Transmission is a major loss of power already. There have been small scale projects to use superconductors for transmission lines which need to be kept very cold but have very high efficiency. Holbrook Substation in Long Island for example has a 600 meter long superconducting line https://en.wikipedia.org/wiki/Holbrook_Superconductor_Project but this is literally multiple orders of magnitude smaller than the distances needed for the proposal,some of which would likely need to go underwater, and there has never been a serious superconducting line run underwater.
And why not wind too? They aren't mutually exclusive. It would provide some power at night time. I believe the Sahara is a pretty breezy place. Am I wrong?
No, you are not - in a general sense, though. There are many places in the Sahara with wind during the night (not to speak about daytime). The problem is knowing exactly where the strongest winds blow during the night. Remember, the Sahara is a more than vast place. Note: I have traveled the Sahara extensively: Morocco, Mauritania, Chad, Egypt. Egypt - the "eastern desert", between the Nile and the Red Sea - had the weakest winds during the night, Mauritania the strongest, and, more important: the most reliably blowing night winds.
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http://www.desertec.org/ They tried to launch an initiative to build solar power in north Africa. However, they did not succeed so far. https://en.wikipedia.org/wiki/...
Solar panels don't like sand storms.
Sandblasting mirrors is bad too.
Actually, sand blasting is much worse for mirrors than for flat-plate photovoltaic panels. Sandblasting the surface of a photovoltaic panel had very little effect-- it roughens the surface, but roughened glass still lets light through. Roughened mirrors, however, while they still reflect light, reflect it diffusely, which is useless for concentrating sunlight.
Dust is a more of a problem, because it sticks, but there again, it's worse for concentrating systems than for flat plate panels, since much of the scattering by dust particles is forward scattering.
http://www.geoffreylandis.com
Except the Sahara is big. Really, really, really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. At 9.4 million square kilometers, it's over twice the size of the EU, and about 6% larger than the contiguous area of the contiguous 48 US states.
So forget the idea of covering all the Sahara with solar plants; it's way too big. Since the idea is to supply Europe with power, you start with the parts that are closest to Europe, which are coincidentally the parts farthest from Boko Haram. Let's say the Mahgreb states of Morocco, Algeria, Tunisia and Libya. These states are unstable by European standards, but they're way more stable than Niger and Chad. Plus they are sparsely populated and conveniently located for NATO military intervention. You could easily fly sorties from land bases in Italy and Spain.
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That's why the new ultra high voltage D.C. systems are being used in places like India, it reduces transmission loss. This is perfect application
Efficiency of power transmission is proportional to the voltage squared.
Quoting any efficiency numbers without specifying the voltage is completely meaningless. The highest voltage lines routinely transmit power economically over thousands of kilometres.
With a DC line the loss can be figured to be due to conductor resistance. A back of the envelope calculation shows that to get 3.5% loss per 1000km would require each pole to have ~5,000mcm of aluminum conductor. At 600kV, it would be a good idea to use a bundle of 4 conductors to reduce corona loss, so each conductor would need to be ~1,250mcm of aluminum, which is a common size for ACSR conductors.
1.1% loss per 100km sounds more like a 230kV AC line.
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The wiki article on HVDC that I referenced above. They got it from a paper from Siemens AG, http://www.energy.siemens.com/...
To quote,
https://en.wikipedia.org/wiki/Inverted_totalitarianism