Subsea battery storage

[Joeboy]

https://www.bbc.co.uk/news/business-60066690

[Oliver90owner]

I did not see any reference to scalability and/or actual storage capacity.

If it is limited to a few MHh, the capital expenditure likely makes it ineffective. Large wind farms require multi-GWh storage, I would suggest?

If there were sufficient wind turbines to allow some to ‘feather’ or even close down, there would soon be some building hydrogen generators for that excess. Not efficient, but who would worry about that in those situations?

Wind turbines simply cannot ‘crank out unwanted/un-needed electricity’ - it must be used, or stored somewhere else - as suggested by the reporter.

[Joeboy]

As the units are relying on few moving parts, no chemical degradation and will provide marine wildlife with reefs I see this application as an excellent example where the relationship between capital expenditure and financial return could be relaxed a little. Used to use N2 charged subsea accumulators and they do store a huge amount of energy. This is very scale-able, I'll be keeping an ear out for when it gets out of proto then test phase.

[AE-NMidlands]

I am sure we have read about this before...

When there is excess electricity the system pumps water from an underground reservoir into tough, flexible bladders that sit on the sea bed. You could think of them like big bicycle inner tubes.


Ocean Battery uses a bladder on the sea bed which holds water under pressure
The water in those tubes is under pressure, so when it is released the water flows quickly and is directed through turbines, also on the sea bed, generating electricity when needed.

I agree that it is sensible to put it in amongst a windfarm (if that doesn't make it just "too difficult") especially as it will avoid storage operators having to pay grid costs when energy goes in either direction.
However this gadget doesn't seem very well thought-out, or the description is crap. If water is taken from " an underground reservoir " then there has to be an air supply to allow the level to rise and fall (perhaps that is what the vertical yellow pipe is) and burying the reservoir looks like causing a major sea-floor disturbance in the first place. It also depends entirely on the resilience of the bladder, and would be less effective at greater depths (where it would have a better chance of avoiding storm damage) due to the opposing water pressure.
I wonder whether it actually works the other way and is being mis-described through ignorance or guile? An unpressurised bladder reservoir on the sea-bed simply as a reserve of clean water that won't mince fish etc, and a pressure vessel below into which you pump water against the pressure of the air it originally contained.
This is the way one proposed system worked, but with reinforced concrete spheres instead and no linked reservoir. I think that a sphere parked on the sea-floor would do less environmental damage during installation, although the bladder system would keep the working fluid "clean."
A

[Countrypaul]

It does give me the impression of being a startup trying to raise money to develop their idea - so we shouldn't be surprised whichever way this goes.

https://oceangrazer.com/

[AE-NMidlands]

I lookedat the video, it does seem cock-eyed to me. When the bladder deflates the pressure it offers falls (unless they are claiming the outside water pressure drives it) but this is just when their rigid cylinder is getting pressurised and offers the most resistance to flow. Working the other way round would probably be better, but I wonder how you maintain and test the underground pressure vessels? I agree that using a captive fluid is better than just the water surrounding it, especially as it will stop stuff growing on the moving parts.
As I said above, I wonder whether they are deliberately mis-describing it so that a copy-cat project is misled...
A

[Joeboy]

Subsea accumulators can easily last for 10 years without maintenance although 5 years was the spec back in the day. I'd like to see N2 charged accumulators used in conjunction with a motor/turbine set. There's enough subsea expertise out there that these could be large modular units on seabed not subsurface. Even the connection to T them into the WT field isn't that difficult to do especially as these are shallow waterprojects. Could be designed to be ROV operated or airdivers.

It's a tiny wee prototype and next step being lake test shows how early it is in developing process.

The more battery projects that can be basic nonpolluting material driven the better.

Looks to me as if it's a surface accessible sealed housing for shallow water. TBH I've not looked at the details as it's recognisable in concept. Best of fortune to them!

[Countrypaul]

Looks to me as if it's a surface accessible sealed housing for shallow water. TBH I've not looked at the details as it's recognisable in concept. Best of fortune to them!

The vertical pipe yousee in thebackground on the picture is supposed to be the wind turbine - not part of the battery (just in case you or anyone else thought that way as it is not clear from your posting)

[Joeboy]

The meat of the system is a high pressure, flexible bladder contained within a concrete reservoir, buried under the seabed. To charge the battery, you pump seawater from the rigid reservoir into the bladder.

Pressure within the bladder does the rest. When extra kilowatts are needed, water is released to run turbines for generating electricity.

The pumps and turbines are based on existing technology and are housed in an accessible machine room.

Above from another newspiece on it

I deliberately left it vague as I can see at least 3 ways it could be built. The wee CG photo is struggling to present in 3d I think. A 20 mtr wd means the housing only has to stand 2 bar at bottom. All electric and moving parts can be housed within the housing and accessed by a shoreside crewboat for maintenance. The accumulators could be hot stackable on seabed in modular frames with enough flexible HP hose that they themselves could be recovered to surface without disconnection. 1st pass at it.

[Bugtownboy]

We can’t be dismissive - cautious maybe - our future power supply has to be (unless fusion delivers) based around RE.

To make this realistic, there has to be storage. Surely a blended approach to providing this has to be part of the solution. The more groups working on a potential solution, the better - one size ain’t going to fit.