By Michael Irving
January 09, 2022
Facebook
Twitter
Flipboard
LinkedIn
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 Photo credit: Ocean
Grazer
VIEW 2 IMAGES
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. Ocean
Grazer
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