this post was submitted on 11 May 2025
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i will try a rough calculations : suppose we can have concrete at $100 per ton, then it's a minimum investment of $40,000. Also suppose electricity is stored with a large added value of 10 cents per kilowatt hour, so, for every cycle a rough gain of $40. By these numbers, 1,000 cycles would pay for the concrete ... so, it may look good considering they plan a life of about 50 years for such devices.
On the other hand if competitive battery storage cost only one cents per kilowatt hour (temporary in and out storage) and if concrete and fabrication goes up 10 times to $1,000 per ton then it is not economically viable anymore.
A good calculation of profitability would need to take into account the less than 100% energy efficiency of batteries cycling and of hydraulic energy cycling, ... and so many more parameters which have to be studied.
Add to this: The chemical process of creating concrete is itself a significant contributor to CO2 emissions. So assuming the goal is to reduce CO2eq, that also needs to be accounted for.
They describe these as giant concrete spheres, but there are (obviously) pumps and turbines involved too, and that those are aimed at a 20-year partial part-replacement lifespan. There's no indication as to how much these pumps/turbines will cost but I'm gonna guess probably more than the cost of the concrete since it's relatively cheap in comparison, and that's before you consider that the major wearing components (which is to say, the expensive stuff) will have to be replaced twice within the intended lifespan. And that's not accounting for things that break and need to be replaced, inside of a giant concrete sphere on the bottom of the ocean where maintenance will be absurdly expensive. Needless to say I'm pretty skeptical of the economic viability of this project. I'd be happy to be proven wrong, but I'm not holding my breath.
i agree with all of this except, you know, when they will have to do maintenance ... i guess they will be (they would be) more simply hauling the whole thing out to work at the surface of the sea ... in this scenario the mechanical components would be at the top of the sphere and out of the water.
Yeah, so instead of sending down divers with equipment you're hauling hundreds of tons of concrete out of the sea, which means aside from a ship and crew which you'd need anyway you're still going to need specialized equipment (some big honkin' chains and winches at a minimum) and tools and such, and that stuff isn't cheap either. Also they're aiming at a 20 year partial replacement cycle for parts that are going to be submerged in or otherwise exposed to sea water which is notoriously corrosive, some of which will be at fairly high pressure (otherwise the turbines will be less efficient), that seems optimistic at best, even if nothing breaks before the scheduled replacement time, and you certainly can't count on that.
You need specialized equipment also if you send down people to do the job that deep. And given you need to use many more specialized people (not everyone can work at these depths and they are not cheap) with all the associated support infrastructures like decompression chanbers and so on. I doubt that the cost will be lower that simply hauling the whole thing out of water.
My point is that whether you send down divers or haul 400+ tons of concrete and equipment up from the bottom of the ocean, it's going to be expensive to maintain either way, especially if things don't go according to plan and they have to perform maintenance more than once every 20 years or whatever.
And my point is that, given how deep these things seems to be, it is cheaper to haul them on the surface than sending a diver down, even if you need to do some unscheduled maintenance, especially because sending down a commercial diver (the only that can hope to work this deep) is not an easy feat in itself.
Obviously it will be expensive either way, I was only pointing out that sending down commercial divers a lot of additional levels of complexity (decompression periods measured in days or weeks, need to hire many more highly specialized people and from a way smaller pool and so on) that will drive up the price.
Did you not catch the part a couple comments ago where I agreed with you? Yeah, of course it's cheaper to not send divers down. All I'm saying is cheaper cheaper doesn't mean cheap. And my larger point is that it's probably not cheap enough, not least because they're planning for a 20 year part replacement cycle on metal bits exposed to high-pressure seawater and that just doesn't seem plausible to me.
Nope, miss it. My bad ;-)
I think that this depends on how much this system can really "produce".
In a 20 years cycle (ok it is theoretical), it does not seems too hard to overcome the maintenance costs, even this high, assuming the production is high enough, which is to be demostrated.
Fair enough.
True. And I did just recently learn that power prices per kWh in California are about double what I'm used to here in Texas, so maybe it's more viable in that market. This just seems like a more complicated, more involved, more demanding version of pumping water into/out of a reservoir on a hill which we already have several examples of that are working great (there are more in the UK) without requiring complex and expensive maintenance and without subjecting pumps and turbines to highly corrosive salt water. I guess pressure in the ocean is easier to come by than hills big enough to create reservoirs on, but..
I'd assume they'd put these pretty close to the surface, lowers the water pressure and makes it more accessible
If you read the article it includes this line:
The pressure is needed to drive the turbine, cause just gently-flowing water isn't going to cut it.