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The story seems so nice, but maths and observations on Quattara basin don't add up. First of all, climate around seas in deserted areas isn't much better than

The story seems so nice, but maths and observations on Quattara basin don't add up. First of all, climate around seas in deserted areas isn't much better than further in land. See the shores in Saudi Arabia, Dubai and Iran. But let's suppose someone decides to build the pipe and extract energy. It means one has to build a 58 km pipe under the ground (which is doable, like Gothard base tunner in Switzerland). Then, 4 issues remain: 1) you must treat the water coming in the pipes, because it's possible to clog the pipe, the turbine, etc. 2) what inclination do you need to get a reasonable discharge of water? 3) how much power one can extract from the flow? Rough estimates give me several megawatts per 10 m of elevation per 1 pipe of 10 m in diameter (this is the kind of size in new large-diameter tunnels). Seems like a lot of piping for not much power. 4) Erosion of the shores that may fill the basin up. This is what happens to natural lakes on plains. And key issue here: the more you discharge through the pipe, the higher the level of water in the lake, the less energy you can extract.

enedil 3y ago
Well, the air in Dubai is much more humid than in Riyadh (this is based on personal observation).
- culebron21 3y ago
  Does it feel better in Dubai than in Riyadh?
mnw21cam 3y ago
2) The Romans used an inclination of 1:1000. The Quattara basin is 80km from the Mediterranean and 60m lower. So it's not looking good straight away. As the water level rises, the drop will be even less. Also, the amount of water that can evaporate from such a large area is immense, so you'd have to have a rather huge channel for the water coming in just to keep up.
- zymhan 3y ago
  The romans were using gravity to move the water "for free". Using gravity to generate electricity is a different concept.
culebron21 3y ago
A little follow-up: 1) the proposal suggests incompatible things: filling the sea, generating electricity from elevation difference (then you shouldn't fill it), and desalinating the water with the energy. If I understand correctly, desalination is very energy-intensive, so it's a big question whether a dam of 60m is enough to desalinate its own stream of water. 2) if it's just a pipe that lets water in, this may be like Garabogazköl gulf in Caspian sea, with salinity levels as high as in the dead sea -- and note that its inflow is 200m-wide canal, not a man-made 10 or more pipe. https://en.wikipedia.org/wiki/Garabogazk%C3%B6l https://en.wikipedia.org/wiki/Garabogazk%C3%B6l 3) costs of digging a trench are at least quadratic to its depth. To have it stable, the trench must have slopes at sides no more than 15%. This means the area of cross-section is depth^2 / 0.15. If it's just 100m, the cross-section is 66K m^2. If it's 200m, it's 266K m^2. At 100m depth, every km of canal is 0.06 km^3 of ground to move. At 200m, it's already 0.26 km^3 -- a quarter cubic kilometer per kilometer of length! Oh, that's why the engineers thought of nuclear blasts here. So, unless humanity is ready to use nuclear weapons that massively, this idea is just a dream contradicting itself.

enedil 3y ago

Well, the air in Dubai is much more humid than in Riyadh (this is based on personal observation).

culebron21 3y ago
Does it feel better in Dubai than in Riyadh?

mnw21cam 3y ago

2) The Romans used an inclination of 1:1000. The Quattara basin is 80km from the Mediterranean and 60m lower. So it's not looking good straight away. As the water level rises, the drop will be even less. Also, the amount of water that can evaporate from such a large area is immense, so you'd have to have a rather huge channel for the water coming in just to keep up.

zymhan 3y ago
The romans were using gravity to move the water "for free". Using gravity to generate electricity is a different concept.

culebron21 3y ago

A little follow-up: 1) the proposal suggests incompatible things: filling the sea, generating electricity from elevation difference (then you shouldn't fill it), and desalinating the water with the energy. If I understand correctly, desalination is very energy-intensive, so it's a big question whether a dam of 60m is enough to desalinate its own stream of water. 2) if it's just a pipe that lets water in, this may be like Garabogazköl gulf in Caspian sea, with salinity levels as high as in the dead sea -- and note that its inflow is 200m-wide canal, not a man-made 10 or more pipe. https://en.wikipedia.org/wiki/Garabogazk%C3%B6l https://en.wikipedia.org/wiki/Garabogazk%C3%B6l 3) costs of digging a trench are at least quadratic to its depth. To have it stable, the trench must have slopes at sides no more than 15%. This means the area of cross-section is depth^2 / 0.15. If it's just 100m, the cross-section is 66K m^2. If it's 200m, it's 266K m^2. At 100m depth, every km of canal is 0.06 km^3 of ground to move. At 200m, it's already 0.26 km^3 -- a quarter cubic kilometer per kilometer of length! Oh, that's why the engineers thought of nuclear blasts here. So, unless humanity is ready to use nuclear weapons that massively, this idea is just a dream contradicting itself.