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Comment by edgyquant | Hacker News Reader

How realistic is it to build and maintain these in a desert? When discussing doing this in the Sahara, there were lots of people claiming that the sand would make maintaining them costly and that at large scales them blocking the sun can actually effect the local climate as it cools the ground and allows rainwater to pool.

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Deserts in the US are not the Sahara - they are large, flat open spaces of hard ground and sagebrush. I'm sure there are still challenges, but if you are envisioning sand dunes to all horizons, that isn't what our deserts look like.

Just for people outside of the U.S., we do also have some deserts with sand dunes.

https://www.blm.gov/visit/imperial-sand-dunes

https://www.blm.gov/visit/sand-mountain-recreation-area

https://www.fs.usda.gov/visit/destination/oregon-dunes-natio...

https://www.nps.gov/grsa/index.htm

https://parksandrecreation.idaho.gov/parks/bruneau-dunes/

Why go to an icky desert to see sand dunes when you can go to the beautiful great lakes and also see sand dunes!

https://www.michigan.org/article/trip-idea/discover-amazing-...

But are any of those in the same area of these 22M acres?

That's mostly true, but there are some ergs (regions entirely buried in sand) in US deserts, and ergs are also a relatively small part of the Sahara.

That doesn't address the cooling effect on the ground, where water could still pool up, does it? Also, a lot of plants and animals live there.

There's already a lot in the desert: https://en.wikipedia.org/wiki/Solar_power_plants_in_the_Moja.... I think maintenance is easier than a hypothetical Sahara megafarm because in the US we can still build them near existing transmission and roads.

They definitely do affect the local climate, and at a very large scale they can hypothetically change the albedo of the desert enough to affect global weather and climate patterns.

Could this be leveraged to mitigate climate change?

Maybe? Apparently if we blanket the Sahara with solar it could actually increase cloud cover and reduce solar potential in a lot of the rest of the world: https://www.nature.com/articles/s43247-023-01117-5.

I guess my answer is no, it would literally cause the climate to change so by definition that's not mitigating climate change. It would be a form of geoengineering, which is sort of its own category separate from mitigation, which refers to action that reduces change.

Any mega engineering like this will have large scale effects on climate and/or ecology

One other issue with the Sahara is that you still have to transport that energy to where it will be used. It's been difficult already to build transmission within the US between a few states. Crossing the Mediterranean and getting the energy across southern Europe (which is sunny and doesn't need it) to cloudier northern Europe would be a lot of permitting. If they can convert the Sahara electricity to liquid fuels, it might actually fit with trade patterns better.

Spain and Morocco are already in the process of building a big solar array in Morocco and a third link across the Strait of Gibraltar (400 kV AC, 700 MW).

https://www.ree.es/en/press-office/news/press-releases/2019/...

It's not especially difficult either from a permit point of view or technically, this is well proven in Europe. See for instance:

https://www.nationalgrid.com/national-grid-ventures/intercon...

"Europe’s electricity system currently has more than 400 interconnectors and is the world’s largest interconnected grid. Currently Europe has around 93 GW of cross-border transmission capacity with a further 23 GW in construction/advanced permitting by 2025"

https://www.schroders.com/en-us/us/institutional/insights/wh...

> and that at large scales them blocking the sun can actually effect the local climate as it cools the ground and allows rainwater to pool.

This is a good thing.

Could this not completely reshape the local ecology?

Almost definitely.

But so will farming it, paving it over, parking over it, mining it for coal or pumping it for oil and gas.

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