… a sphere nine metres in diameter and weighing 400 tonnes will be submerged off the coast of California at a depth of 500 to 600 metres. It will have a storage capacity of 0.4 megawatt hours (400 kWh) …
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.
I think I understand how the battery where they drop a big weight down a mountain works; how do these work? Or how does it compare in effectiveness as I assume it’s probably the same principle?
It has a turbine inside it. It is not a cement ball, it is very misleading title. It’s a cement shaped hollow orb with a hydro power generator inside it.
Well that sounds like cheating.
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.
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
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
Plus the places most suited for dams also tend to be natural wonders. Rip Glen Canyon and Hetch Hetchy
Or places which are already heavily inhabited/productively used. Inland river valleys are some of the most desirable real estate, in human habitation terms.
Major river dams are often only feasible in countries which either have lots of sparsely populated wilderness (like North America), or which don’t have a problem with displacing hundreds of thousands of people and destroying whole communities (like China). Takes it off the menu for a lot of the world.
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.
Now imagine this 27 foot wide ball shooting water out of its bottom while on the sea floor and tell me there’s still no silt being stirred up. Or algae. Or mineral buildup.
That’s why I said siphon it from the bottom, a siphon tube going from the bottom to the top would eject the water up and away while still sucking out most of the sediment that had gotten in and settled on the floor of the ball.
The sediment that gets pushed out into the surrounding water. That gets pulled up with the ball as it creates negative pressure behind it as it rises.
Bro, the ocean is FILTHY. Like, crazy filled with stuff. Like, you could take a coffee filter and pull stuff out filthy. Like the water has so many living organisms in itself it’s basically alive.
And let’s talk about the salt. Corrosive af salt.
This isn’t impossible, but the people trying to point out why this is CRAZY difficult are right. This will not be a set it and forget it scenario by far. It will need regular maintenance. The issue is whether that maintenance is easier or harder than a dam or stationary tank.
Like, why can’t we build these in giant freshwater reservoirs? Stick them a pool. Or why does it need to float? Wouldn’t a tank at the bottom of a pool with a pump do the same thing? Or two tanks at different heights with a conection between them and a pump? This is just mechanical energy being stored for later. Do the work when it’s cheap and reclaim it later.
They don’t float, they’re fixed in place at depth. They use the pressure of the surrounding water to spin a turbine as its pumped in and out, the only moving parts are the turbine and its associated components. And seeing as how the water is pumped in and out, most of the silt/detritus pulled in during filling, would be pumped out during draining assuming a siphon tube is used to draw the water from the bottom of the sphere (where all the debris settles) to the pump.
Yes salt water is corrosive, but that problem is already solved, there are currently concrete oil platforms built in the 70s and still in service today. We have formulas for concrete that are proven to be seawater resistant.
Building storage tanks on land wouldn’t be as efficient due to the greater pressure differential at 500m underwater vs on land. Dams are one of the most expensive structures to build and are very damaging to the surrounding environment. They also have a much larger problem with silt deposition as there is a constant flow of it, every time it rains there’s another surge of silt making its way downstream to be trapped by the dam.
Overall this project would be considerably cheaper, more friendly to the environment, and most likely more efficient than any pumped storage on land. And its not like the sea floor is lacking for real estate, unlike any feasable locations for dams here on land.
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
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.
Really good points. I was only thinking of the structure of the concrete… Sea life growth is a whole other ball game!
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.
