Energy

Ocean Battery stores renewable energy at the bottom of the sea

Ocean Battery stores renewable...
The main components of the Ocean Battery system: the flexible bladder (top left), the concrete reservoirs (bottom left) and the machinery units (yellow, center) containing pumps and turbines
The main components of the Ocean Battery system: the flexible bladder (top left), the concrete reservoirs (bottom left) and the machinery units (yellow, center) containing pumps and turbines
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The main components of the Ocean Battery system: the flexible bladder (top left), the concrete reservoirs (bottom left) and the machinery units (yellow, center) containing pumps and turbines
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The main components of the Ocean Battery system: the flexible bladder (top left), the concrete reservoirs (bottom left) and the machinery units (yellow, center) containing pumps and turbines
A diagram of the Ocean Battery system. When charged (left), the bladder is full of water and the concrete reservoir is empty. When the battery is discharged (right), the bladder is empty and the reservoir full.
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A diagram of the Ocean Battery system. When charged (left), the bladder is full of water and the concrete reservoir is empty. When the battery is discharged (right), the bladder is empty and the reservoir full.

As useful as renewable energy sources are, they need to be backed up by storage systems that hold energy for times when the Sun isn’t shining or the wind isn’t blowing. Ocean Battery is a new design for an energy storage system that functions a bit like a hydroelectric dam at the bottom of the sea.

Developed by Dutch startup Ocean Grazer, the Ocean Battery is designed to be installed on the seafloor near offshore renewable energy generators, like wind turbines, floating solar farms, tidal and wave energy systems. It is made up of three components that together function on a principle similar to that of a hydro dam.

Buried in the seabed is a concrete reservoir that holds up to 20 million liters (5.3 million gal) of fresh water, stored at low pressure. A system of pumps and turbines connects this reservoir to a flexible bladder on the seafloor. Excess electricity from the renewable sources can be used to pump water from the reservoir into the bladder. When the energy is needed, the bladder releases and, driven by the pressure of the seawater above it, squeezes its water back down to the reservoir, spinning turbines on the way to generate electricity that’s fed out into the grid.

A diagram of the Ocean Battery system. When charged (left), the bladder is full of water and the concrete reservoir is empty. When the battery is discharged (right), the bladder is empty and the reservoir full.
A diagram of the Ocean Battery system. When charged (left), the bladder is full of water and the concrete reservoir is empty. When the battery is discharged (right), the bladder is empty and the reservoir full.

The Ocean Grazer team says that the system has an efficiency of between 70 and 80 percent, and should be able to run an unlimited number of cycles over an operation lifetime of more than 20 years. It’s also fairly scalable – each concrete reservoir has a capacity of 10 MWh, so adding more of these can increase the overall capacity. Extra units of the pump and turbine machinery can also be added to boost the power output, if more energy is needed quickly.

The Ocean Battery concept is intriguing, but it’s far from the only ocean battery design in the works. Subhydro outlined a similar idea to pump seawater out of tanks placed at the bottom of the sea, then when electricity is needed the water is let it back in, spinning turbines as it fills the tank. MIT also described a similar concept using hollow concrete spheres. Another recent design worked off buoyancy, using electricity to drag and hold balloon-like containers underwater, then releasing them to generate electricity.

Still, there’s not going to be one solution that suits every situation, so solving a global problem like renewable energy storage is likely going to take a whole army of these different, creative ideas.

The team describes the Ocean Battery in the video below.

Ocean Grazer - Ocean Battery – Utility-scale offshore energy storage

Source: Ocean Grazer

13 comments
13 comments
Jim B
No real volume = no real energy storage, the amounts of water stored behind dams are massive. Could be used for short term load balancing, but then it would probably be much much cheaper to use pumped hydro on land.
dan
similar techniques applied in mountains or no more used mines deep below surface, mountains and old mines are already there... so, this startup need to be very, very efficient to become competitive!!! But for short term (some peak hours maybe?) could be good! Go for it!
windykites
Pump maintenance would be a problem. Using seawater would obviate the need for the concrete tanks, or just pump air! Install the pumps above water, for access.
highlandboy
Just like liquids are not particularly compressible, they don’t readily expand. The concrete bunker will need some gas to slow the water to be pumped out. Unfortunately when you let the water back in (through the turbine) the gas will be under pressure. Gasses under pressure dissolve into the liquid. So now there needs to be a way to replenish the gas.
The other issue is buoyancy, even concrete ships float. The amount of dense mass required to keep the concrete bunker down would be considerable.
Working around these two issues, even without the costs of initial construction, is likely to make this system unviable.
Rumata
The efficiency might not be as high as expected, because most of the compression work will be lost as the compressed gas cools down in the "bladder".
Also, the price of concrete structure might be too high to be economical.
Clearly, it is not a viable concept.
vince
Better to just take the mountains of trash we dispose of in landfills and dump on barges. Tow them to a deep 25,000 foot trench and let the weight of the material fall to the bottom of the trench and recover the potential energy difference using the old formula F = Work * Distance.

Of course, this will pollute the oceans so never mind its a fail fail. Or you could use the tailings recovered from surface mining and dump those into the sea. That would pollute the oceans too. Never mind another fail.

Or we could just capture all that hot air in DC wasted on bickering and the energy recovered would save the world. That ought to work.
michael_dowling
Jim B: Pumped hydro is site dependent,and most of the best sites have be developed. For storage of solar/wind excess power,liquid air storage systems would likely be better,as they are situated on land,and the technology is well understood,and they are not site dependent.
guzmanchinky
Does this seem overly complex in an extremely harsh environment, or is it just me?
Chase
Looks to me like they are just trying to trade screwing up the earth's surface for screwing up the sea floor.
DavidB
From reading these comments, I have to say that it’s surprising there are so many hydrology and electrical engineering experts among New Atlas’ readers.

What in the world was this Dutch company thinking? They should’ve run their product concept past this august group before building something these respected experts have easily explained is certain to fail.

LOL
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