We are currently in the middle of a renewable energy boom.
Finally, after a long history of complex energy crises and health
issues caused by our reliance on a fossil fuel energy system, in
addition to environmental damage and decades of knowing that we
needed a more sustainable energy system to combat climate change,
finally now alternative energy has become an actual plausible
alternative to fossil fuels, we've reached the point where
renewable energy is not only a better environmental
alternative, but also proving to be a better answer to the other
two big issues of energy supply: energy security and cost. But of
course, such a huge transition doesn't come without challenges.
as cheap as wind and solar have become, we're not going to get
far enough with these technologies if we can't solve
the problems of: 1. Where to put all the new wind and solar farms
we need to totally replace fossil fuels and 2. How to match
the variable generation from weather based renewables to
human demand. Offshore energy provides part of the solution to
the first question and energy storage provides part of the
solution to the second. In this video, I'm going to talk about a
group of emerging technologies that combined the two: ocean
energy storage. I'll talk about what it is, how it works, why
there are so many companies working on this all of a sudden
and then mention some of those developing technologies in this
very new space. I'm Rosie Barnes, welcome to Engineering
with Rosie. Ocean energy storage is a broad category of a whole
heap of different methods of generating and/or storing energy
in the open ocean. It's an area that has recently experienced a
huge surge of interest with probably dozens of new startups
in this space in recent years, mostly still at very low
technology maturity levels. The companies that I've seen
developing ocean energy storage systems pretty much all use one
of three operating principles: pumped hydro, gravity and
buoyancy. Underwater pumped hydro systems work roughly like
onshore pumped hydro, where a turbine is located between two
reservoirs with a pressure differential. When you want to
generate electricity you allow water to flow from the high
pressure reservoir through the turbine to the low pressure
reservoir and when you want to store energy you pump water in
the opposite direction. For onshore pumped hydro the
pressure difference comes from having one reservoir at a higher
elevation than the other, and for underwater pumped hydro the
pressure difference typically comes from hydrostatic pressure
deep underwater. This is the most common option chosen
amongst the more mature ocean energy storage companies out
there today. The Ocean Grazer system has a pump and a rigid
concrete reservoir buried in the seabed and a flexible bladder on
the surface on the seabed. To store energy, it pumps water
from the rigid reservoir into the flexible bladders storing it
under hydrostatic pressure. To discharge, the water is allowed
to flow back into the concrete storage which turns a turbine
generating electricity. Ocean Grazer has successfully
demonstrated a small scale prototype in 2021. And their
next planned step is a 10 MWh 70 by 70 meter installation in a
flooded quarry connected to floating solar panels. FLASC is
a floating platform that stores energy by pumping seawater into
an underwater chamber. The seawater compresses air in a
separate chamber and when energy is needed, the air is allowed to
expand to push the pressurized seawater powering a turbine.
They successfully demonstrated a small 530 Wh prototype in 2017
in the Maltese islands storing energy generated from PV panels.
StEnSea is an underwater pumped hydro storage system originally
developed at the Fraunhofer Institute in Germany. It's made
up of hollow concrete spheres installed on the ocean floor.
They start off filled with seawater then to store energy
the water is pumped out into the ocean. To discharge, high
pressure water is allowed to flow back into the sphere
through a turbine. They successfully demonstrated the
technology using a 1:10 scale 4 kW system in Lake Constance,
Germany in 2016 and they're now hoping to secure funding to
trial a 5 MW/22 MWh system at full depth.
The next category of underwater energy storage is gravity
storage. This is similar to onshore gravity energy storage
systems that I've covered on this channel before like
Gravitricity or Energy Vault. Gravity energy storage simply
involves taking a mass and raising and lowering it when you
want to store and generate respectively. Typically, an
electric winch is used to raise the mass which then acts as a
generator when it's lowering the mass. The physics behind it is
very simple. The amount of energy stored is simply m x g x
h (mass times gravity times height) and offshore where the
ocean is very deep that 'h' can be very large. Ocean Hydro is
developing a combination of offshore wind and energy
storage. They've completed component tests in test
facilities and are currently installing a prototype system
that will be tested in the ocean. The prototype system uses
a 5 kW floating vertical axis wind turbine which is directly
connected to an electric winch that raises and lowers a mass to
store and generate electricity. In the configuration shown here,
with a single mass per turbine, it doesn't really function as
storage, but it could be designed with an array of
turbines and multiple masses per turbine which would allow energy
to be generated and stored. And I should just quickly disclose
that my company Pardalote Consulting has done some work
for ocean hydro in the past though they are not sponsoring
this video. Sinkfloatsolutions is another company with an
offshore gravity energy storage idea. They hope to develop a
floating barge with a hoist unit that lifts weights to store
energy and lets it sink to generate.
And finally we have buoyancy storage, which doesn't really
have an onshore equivalent, but I think of it basically like the
opposite of gravity storage. Instead of gravity pulling a
heavy object down a low density object like a balloon is pulled
underwater to get a buoyancy force that wants to pull the
object back up. You pull the buoy down when you want to store
energy and you let it float up when you want to generate. If
you ever did swimming lessons as a kid and sat on your kickboard,
you might have experienced the power of buoyancy energy storage
if you accidentally slipped off and got the kickboard to the
chin. I definitely did that. The few companies that I've seen
developing buoyancy storage are at low maturity. Little more
than just like an idea, some sketches and currently
non-functional website at this point. An example is Lift
Renewable Energy who wants to store energy inside of
gas-filled balloons underwater. An electric winch would drag the
balloon to the seabed. To discharge, the balloon would
then be allowed to float, dragging the winch with it to
the surface and thereby generating electricity.
If you want to learn more about how these types of systems work,
then you can head to Brilliant who are the sponsor of this
video. Brilliant is a website and app with over 60 Interactive
courses in math, science and related topics like engineering.
They have interactive courses on all the basic physics principles
that I've used today: gravity, pressure and buoyancy. So you
can dig deeper into these concepts and learn all the
equations you need to make your own judgments about each of
these technologies or even come up with your own design if you
think you can do better than the ones I've shown you today.
Brilliant uses interactive exercises on everyday examples.
So you learn by doing not just memorizing, this helps you
develop an intuitive understanding of how the world
works and how engineers can take advantage of physics principles
to solve important problems like the need for energy storage. You
can get started on brilliant for free, and for Engineering with
Rosie viewers Brilliant is offering 20% off an annual
subscription for the first 200 viewers to sign up, you just
need to go to brilliant.org/EngineeringwithRosie,
I'll put the link in the description.
So that's the 'what' of ocean energy storage. Let's move on to
the 'why'. And I think this is the most important question for
ocean energy storage because it does break one of my fundamental
rules of technology development, "never put something offshore
that could be onshore instead," the reason that I have that rule
is that it takes so much longer to develop anything offshore and
it costs so much more to install or maintain something offshore
compared to onshore. The ocean is an incredibly harsh operating
environment, which means materials cost way more and
failures occur way more frequently. And so they need way
more maintenance which takes way longer because you need to wait
for weather windows and then transport crews in ships or
helicopters. And then anything underwater needs to be either
dragged above the surface for maintenance or it needs to be
maintained by divers. That is all just such a huge pain that
any sane product developer would avoid that whenever possible. So
why would you bother with offshore energy storage at all
and not just put say, a lithium ion battery or pumped hydro
system onshore, if you have an offshore wind farm or floating
solar or even you know, wave or tidal power, they may be located
offshore, but the electricity they generate is probably going
to be used onshore. So there's no reason why you couldn't just
stick a battery there. If you check out their websites, most
of the ocean energy storage companies say that they're going
to be cost competitive or cheaper than mainstream energy
storage technologies like lithium ion batteries for short
duration storage or pumped hydro for longer duration storage. But
since these companies are all in fairly early stages of
development, I mean you decide for yourself how much weight
these predictions should carry when they haven't yet got any
operational data to justify their claims around you know,
maintenance costs and operational lifetimes. There
could well be some infrastructure savings if these
technologies are combined with offshore generation assets.
They'll be able to share subsea cables and perhaps moorings with
you know, say an offshore wind farm but still anything offshore
and anything new is going to be expensive to start with and
competing technologies are generally getting cheaper and
cheaper. On the other hand, there are a lot of people out
there predicting that lithium ion batteries are going to
become more expensive in the future as demand grows faster
than the supply of battery materials like lithium, nickel,
and maybe others, cobalt, manganese and graphite for
example. I personally think that if there are issues like that
there'll be short lived as new mines and/or new battery
chemistries that don't use constrained minerals will fill
in the gaps. But it's certainly a possibility that they get more
expensive. All of the technologies I've mentioned in
this video are mechanical systems that shouldn't need a
lot of critical minerals so that's one potential advantage
if it does turn out that lithium ion batteries become expensive.
But I think the really strong case for ocean energy storage
techs is going to be applications where they're doing
something that onshore energy storage can't easily do. So that
might be supporting energy supply to offshore applications.
For example, deep sea mining or offshore oil and gas projects
where the power never needs to go on shore at all. Of course,
you can stick a lithium ion battery or even a hydrogen
electrolyzer tank on an offshore wind turbine to get remote
generation plus storage. But in that case, you'll still suffer
from many of the same environmental challenges as the
ocean energy storage so the cost advantage wouldn't be as great.
Another possibility for ocean energy storage to do something
that onshore can't easily do is when really long duration energy
storage is needed. And another option like pumped hydro isn't
there for example in places with no hills nearby, going offshore
allows the whole ocean depth as you're working height and also
large pressure differences compared to onshore
possibilities. The Fraunhofer Institute have published a
techno-economic assessment about the conditions needed for their
underwater pumped hydro system StEnSea to be cost competitive
with other long duration energy storage, assuming their
assumptions related to cost are realistic. They say that they
need water depths of 600 to 800 meters within 100 kilometers of
an electrical grid, and they reckon that there are suitable
locations to install up to 817 TWh globally. Underwater
installations are also out of sight and not in anyone's
backyards. So it might be easier to get community acceptance for
the very large installations that will be needed for long
duration storage. And perhaps the environmental impact will be
lower. Though the ocean obviously has its own ecosystems
and threatened species so we won't actually know whether the
environmental impact is low until it's studied. And then
finally, there are potential synergies between new offshore
generation and storage. Ocean Hydro, for example, using
gravity storage that's directly coupled to floating vertical
axis wind turbines. The wind turbines themselves don't have a
generator, they simply raise masses quickly when there is a
lot of wind energy available at high wind speeds. This means
that they don't need to limit power output when high wind
speeds provide more power than the generator can handle. In
this way ocean hydro intend to increase the annual energy
production of offshore wind compared to traditional offshore
wind power. So ocean energy storage has some big potential
advantages, but in my opinion, it's far from certain that we'll
need these techs. Everything they do can be done by existing,
more mature technologies. Since there's no absolute necessity,
they'll need to compete on other factors. Each of the ocean
energy storage companies is going to want to be realistic
about the price point they need to achieve. And for early
installations while the costs are still high, I think it would
be a good idea for them to focus on niche applications where more
mature and cheaper technologies just can't go. Throughout the
rest of their development journeys ocean energy storage
companies are going to face a lot of surprises, a lot of
setbacks, and they will do well to learn from the experience of
other ocean technologies that have come before like wave,
tidal, offshore wind, to save themselves some teething pains.
If you look back through the history of wave energy
companies, a lot of really good technologies fail from really
mundane issues like off the shelf components failing in
their prototype, which caused month long delays and large
extra cost just trying to get a maintenance crew out there to
swap out a simple component. In one of the early videos I did on
wave energy, a researcher I spoke to said that you really
need to have patient capital that can weather repeated
setbacks like that, and I think that that will apply to ocean
energy storage as well. Another industry that I think ocean
energy storage can learn from is offshore wind which matured
their technology onshore before taking it offshore. There were
still many surprises and setbacks in early offshore wind
and floating offshore is still in that period of rapid learning
by failing but the number of failures was minimized by having
solved most issues onshore where everything is cheaper and
easier. And if you look at the difference in how fast offshore
wind has developed versus say, wave or tidal energy, I think
that head start being able to iron out a lot of kinks in the
design onshore has been a crucial differentiator. Thanks
to everyone in the Engineering with Rosie Patreon team. Their
support allows me to pay a small editing and research team for
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staying up to date with real energy technology engineering at
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link. Thanks for watching and I'll see you in the next video!