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They're going to...pull a vacuum in a concrete sphere deep underwater. And then use the force of water being sucked back in to turn a turbine.
...sure.
High social acceptability: Installed far from inhabited areas, these facilities arouse less opposition.
Actually, being very close to inhabited areas, but 0 impact, including nonsensical nuissance arguments, means short power transmission. It's also very easy to pair with offshore wind.
Sounds interesting, but considering how thick hydroelectric dams need to be to hold back a mere lake, how thick are these spheres going to be to hold back an entire ocean?
Wow, someone invented upside down pumped storage.
Each sphere has an estimated lifespan of between 50 and 60 years, with partial replacement of components every 20 years or so.
The concept is fascinating, but what I'm most curious about is how they achieve that longevity in seawater. Benthic life really loves to settle and build on hard surfaces.
Every time I see these “We’ll do X in/around the ocean” projects I think, “These people have not spent a lot of time near the ocean.”
There are 2000 year old Roman concrete piers that are still just hanging out in sea water. So it's possible if you find the right mix.
The concrete isn’t the problem. Like mentioned above, the sealife growth is. Also, metal and moving mechanicals are savaged by seawater (and the sealife growth). Keeping things working on the surface of the water is difficult and expensive. Water pressure makes that even worse. Maintenance requires divers which are likewise very expensive.
I think the sea has a huge potential of energy production that is totally untapped because of that.
There are tons of ways to produce energy with sea water but as soon as you put any moving parts in water it gets corroded and covered with benthic life (I've learned a word today). Every project of ocean energy production dies because of that.
Benthic Life needs to be band/album/movie title.
Unfortunately, you can't see BENTHIC live.
They don't have a tour planned.
https://lifeforcerecords.com/archives/artists/benthic/
Of course they’re not touring. They’re sessile.
I would like to know what is the % of loss when storing power as any energy conversion is not lossless.
Cheap storage is more important than conversion ratio. Enough renewables leads to periods of negative prices without matching storage capacity. Storage can mean 1-2c/kwh charging costs, and even 50% efficiency makes discharged power 2-4c/kwh.
if 0.5m thick sphere, 30m diameter is 1413 m^3 of concrete. $300k to $400k in materials. Stores 150mwh power. About $2-$3/kwh
Regular pumped hydro has an overall efficiency of about 80%. I would guess these sphere things would be similar, assuming you can put them near a high-voltage line, since the underlying technology (pump and turbine) is the same.
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.
The most pressure it would experience would be the difference in internal vs external pressure. At 1000ft of depth there’s a pressure of 440psi. Assuming the sphere somehow managed a perfect vacuum that’s still well below the 6000psi compressive strength of high strength concrete, hell they would still have more flexural strength. The spheres themselves definitely wouldn’t be the weak link.
It seems to me pumping out water to near vacuum while under crushing outside water pressure would be a significant power hog
Well, yeah. That's the point. It's a battery. Whatever energy you put in to pump the water out, you get some percentage (probably in the 50-70% range) of it back when you let the water back in. The point of these is to store energy from renewables whenever they are providing more power than the grid demands - otherwise the power would be wasted.
Edit: The paper claims 72% efficiency which is pretty good if I understand things correctly
Yeah don't get me wrong- I get it’s a battery. But a battery that’s 5% efficient isn’t great. Now 72? That’s pretty incredible, I’d like to see that in action.
I don’t know what depths we’re talking about here,
From the article:
The idea is relatively simple: hollow concrete spheres are installed at a depth of several hundred metres.
Thanks, I missed that on my read through - 1000 feet of water is pretty serious pressure.
The more pressure the more "equivalent head" power discharge potential. Separate "vacuum pump" (instead of bidirectional) could also have several stages to improve efficiency.
Interesting concept, but not very scalable. It's basically a reversed dam - when it's full, there's 0m head of water. Then with excess energy, you lower the level inside, storing the energy in the water outside. E.g -2m head. Water then flows in to equalise head, and doing so, regenerates electricity. Adding depth to supercharge pressure differentials is a good idea, although I wonder how they limit the flow rate, or otherwise prevent cavitation shocks each cycle.
Could be useful as a private industrial battery, but a dam would still be better on an infrastructural level.
Dams do have their own significant challenges with habitat destruction and displacing people and silt buildup
Dams have issues around silt buildup over time and to the best of my understanding the US is already dammed to the max (within reason).
I'm keen to see how it pans out. Seems like a very interesting concept.
damned to the max
Silt did not magically disappear because your dam is spherical, and there is a lot of it on the sea floor. They need to install some kind of filtering system anyway.
Also, the lifetime of a sphere is estimated to be 60 years, while the traditional dam is engineered for 100+ years of service.
The main advantage is that the sea floor is unused and unregulated like the dry land , but then you could as well build an actual scuba diving underwater base with a hydro dam instead of a sphere, it will also be easier to clean and repair, but I guess that would be too much evil moustache twirling to get funded.
I don't see silt being as big of a problem here, if the intake is located at the top of the sphere that puts it well away from the seabed. The only silt it could suck in is what's dispersed in the water already, and at 500+ meters there's very little current to stir it up. And if they put the intake on top and siphoned the output from the bottom it would even be relatively self-cleaning.
Did they say it was intended to be on the seafloor? I didn’t see that but assumed it would be moored deep enough for water pressure to turbo boost the turbines, but well clear of silt from the sea floor. That would also be a key benefit if you can moor it at the most useful depth but in any depth of water
The article say about 500/600 meters deep. No mention if on the sea floor or not.
Like a battery, it’s not scalable as a one off, but it may be as a modular mass produced item.
Or maybe like a wind turbine. You’d have a field of them comprising a power plant. If you lose some individuals, who cares. If you need to do maintenance you can take one offline or entirely replace it without really impacting the power plants output
An easy manufacturing method would be to 3d print in plastic a double walled shell, with fill holes for concrete, and mounting chanels for motors. Plastic "lining" would provide salt water protection for the concrete.
We have seawater resistant concrete. We don't need to plastic line it. It's the turbine that'll require the most maintenance.
Depends if the spheres require any steel reinforcement; the salt penetrates the concrete and absolutely wrecks rebar. Though I imagine spheres at depth (not to mention with a partial vacuum) can function like an arch and support themselves with compression, which concrete excels at.
They need to pair this with Tidal power
Tidal power probably needs shallow water while these would be great in deep water
Why not submerge a tank with a hole at the bottom and blow air in the tank via a hose to store energy?
The adiabatic compression of gas makes this highly inefficient.
this post was submitted on 11 May 2025
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