I’m pretty skeptical about this- wouldn’t a 30m sphere be incredibly buoyant when empty? I get its concrete, but it’s displacing huge amounts of water. So you’d need some massive anchoring, maybe that’s not a big deal. Second, I don’t know what depths we’re talking about here, but I feel like the stress from cycling these things daily would be insane- in high pressure salt water no less. I also wonder what the efficiency of this system would be compared to other similar batteries, like pumped hydro storage. It seems to me pumping out water to near vacuum while under crushing outside water pressure would be a significant power hog.

[–] A_A@lemmy.world 2 points 1 month ago (5 children)

... you’d need some massive ...
from the srticle :
... a sphere nine metres in diameter and weighing 400 tonnes will be submerged ...

Can you calculate the weight of a sphere of 9 m of displaced water ?
No ? Well, it is 382 tons.
So, the concrete sphere is already massive by itself. "You" don't need any complicated anchoring.
Same goes with the rest of your mechanical engineering intuitions : you did not work in this domain or study it, did you 😆 ?
Also, stress cycling is bad on most material, yes. But here it is compressive stress and the geometry is symmetric. Without further study, i want to believe this thing has good potential and my intuitions tells me it looks nice. Time will tell 😁 !

[–] towerful@programming.dev 14 points 1 month ago (1 children)

Can you calculate the weight of a sphere of 9 m of displaced water ?
No ? Well, it is 382 tons.

Metric strikes again.
I bet you didn't even have to convert through football fields, elephants, or olympic sized swimming pools!

[–] A_A@lemmy.world 3 points 1 month ago

indeed i made a very simplified calculation not taking into account increase density of salted water nor increased density because of compressibility of water at 500 m deep. Basically i took 1m³(water) is 1 (metric) ton.

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