It sounds quiet inefficient to me. The energy differential comes from the different salt concentrations, so you have to move a lot of water to exploit a relatively low mass differential.
Mentions of efficiency are conspicuously absent from the article.
Another potential problem is marine ecology: pumping high-salt sea water to the top and releasing it en masse might lead to much larger fluctuations in salt concentration than what the ecosystem is used to.
That said, we need many different approaches to solve energy storage, and I hope to be wrong, and that they end up very successful.
Yeah no mention of how it would effect marine ecology is bad, but the avg startup/mega-corp doenst care see how far people are trying to make deep sea mining legal, even with its obvious implications of destroying the sea
[Company] has tested a small model of the reservoirs in wave tanks and off the coast of Reggio Calabria, Italy. It’s now deploying a pilot of the floating components in advance of a full demonstration plant. By 2026, it’s hoping to deploy several commercial projects at sites around the world.
At full size, the turbines would generate around 6 to 7 megawatts of electricity each, and there will be one for every 100 meters of pipe. Deeper sites would have more storage potential, and each commercial site would host multiple reservoirs. Sizable hopes to deliver energy storage for €20 per kilowatt-hour (about $23), about one-tenth what a grid-scale battery costs.
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Testing in calm reservoire is different from potentially .wild offshore (ocean/sea)
What happens to 100-200 m long pipe in underwater waves when e.g. a hurricane or a storm comes?
Even in a storm, just a few meters below the surface (half the wavelength), the sea will be calm.
The bigger issue with this idea is that it's a megastructure sitting in the ocean, and salt water turns everything it touches into shit. Oh, and there's very little energy storage potential from just a salt gradient. You need to move way more water, to get less energy, but your container costs are fixed.
Land-based pumped hydro has no shortage of engineering problems (and risks if, you know, you get a dam collapse), but this has colossal capex costs.
My understanding of this technology is that it's closed-circuit. No water is exchanged between the power plant and the ocean once filled with ocean water.
What I don't understand is how the top reservoir is floating when filled with brine. Are the small floaters enough to hold it up?
Otherwise I love the fact that's simple. Simplicity scales.
It's also salt water, so assuming they're not putting anything else than NaCl, it can break and it's no big deal
Have some air at the top of the top reservoir, assuming that the top reservoir is at most about 10 m deep in water (to avoid damage from storms). Or have the air in separate chambers fixed to the top reservoir.
- they concentrate salt water once to get "heavier than sea water" brine. Hope not chlorinated.
- it's then a closed system shuffling between bottom and top tank(s)
- everything floating is soft, so no strong forces unless a wave crashes on top
- advantage of ocean: "free standing" within height/depth margins, free water for initial fill
And really not visible in the video:
- the disk you see floating is a V shaped bladder with the storage in the V below surface and floatation sprinkled all around and segmented in to "cake wedges".
The maintenance on this will be a real killer and by the time you build the robotic infrastructure to maintain it you’re not a power company anymore kindof how Amazon isn’t a bookseller.
Wait a second $23/kWh? I pay ~ $0.15/kWh for power at my residence the majority of the year. Is this a proof of concept number? What am I not understanding such that the power this produces is 4 orders of magnitude more expensive than what’s in place currently?
It's like saying gas at the pump costs you $3/gallon but building a storage facility costs $100/gallon. Yes, they're both $/gallon, but these aren't the same measurements--one is for a gallon of dispensed gasoline and one is for constructing storage with the physical capacity of a gallon. One is the price of gas and the other is the price of storage. You can store and then dispense many, many gallons over the lifetime of that one-gallon storage.
They're not dealing with a pressure differential. Or at least I don't think so.
I don't think the Journalist who wrote the article understood the technical details, but from digging a little at their website I think what's going on is they're moving heavy brine up and down, all of it equalized with local pressure.
Despite them describing it as pumped hydro, I think its better framed as a cousin of the "chunk of concrete suspended over a mine shaft" style gravity battery. Replace the mineshaft with water and the concrete with salt.
Relying on a salinity differential, even between salted and unsalted, seems like a terribly small amount of energy. There are projects to put large spheres at the feet of offshore windmills to pump water in and out. That has some pressure challenges but store a lot more.
The advantage I see for the salinity difference is that you can make them a lot larger than the pumped water ones. But is worth it, I'm skeptical.
I don't think it is a problem for the outside shell, or maybe just a minor one. For the interior of the reservoirs, I guess the hyper salty water will kill everything that tries to grow there.
It depends on the definition of "near", but there's a sizeable population within ~40km, which is a reasonable distance for an offshore wind-farm.
Almost the entire Mediterranean is >500m depth within just a few km of the shore, and that's half a billion people. All of the eastern seaboard of the North+South American continent is available at 100km distance (another 100-200mn people). Most of west Africa, all of Australia, and almost all of the western flank of the Pacific.
Maybe a quarter of all people live within 40-50km of a 500m deep sea. Definitely a large TAM.
And under water construction is expensive. And durable construction in a marine environment is challenging (and makes things more expensive).
That doesn't mean it's a bad idea but they are factors that add to the overall cost. 20$/kwh is very attractive of course. But that's also a number that e.g. CATL is chasing with sodium ion batteries. And they are going to be making those by the gwh/year from next month.
This seems like it could mess up local weather by bringing up water of different temperatures if deployed at scale (and if not at scale, what's the point?).
> if deployed at scale (and if not at scale, what's the point?).
The "at scale"s might be very different between "what would be enough to affect local weather" and "what would store all the excess electricity generated in non-peak hours".