Lithium ion batteries are
incredibly appealing for EV applications because they can
pack a lot of energy into a small and light package. But for
stationary storage, the size and weight don't really matter. What
does matter is cost especially when you need longer storage
durations of 10 hours or more. To double the storage duration
of a lithium ion battery you pretty much need to double the
cost but that's not the case for flow batteries, which is the
topic of today's video. Flow batteries are a type of
rechargeable battery that uses two chemical components
dissolved in liquid electrolyte, the electrolyte is stored in
external tanks and pumped through a reaction chamber to
produce electricity. Last year while I was in Brisbane, I had a
chance to tour a hybrid flow battery manufacturer Redflow. In
this video we're going to look at how their batteries work, how
they're tested and how their design has evolved over the
years. I'm Rosie Barnes, welcome to
Engineering with Rosie. I was keen to visit red flow because
while the hype around flow batteries is a pretty recent
thing, these guys are no spring chickens, they kicked off pilot
studies back in 2010. And by now there are Redflow batteries in
over 250 sites. Originally, they were just selling single 10
kilowatt hour batteries for residential and remote sites,
for example for communications, but these days they're looking
at large modular systems in the tens to hundreds of megawatt
hours. So first, let's just quickly look at how a Redflow
battery works. Then we'll start the tour and some of the Redflow
staff will explain each component in detail To charge the battery,
electrolyte is pumped through two half cells in the battery
stack. In one half cells, zinc ions gain electrons and become
metallic zinc which collects on the electrode and the other half
cell bromide loses an electron and becomes complex bromide,
which deposits on the other electrode. The first half of the
process uses electricity to power the pumps. And then to get
that electricity back the reactions run in reverse and
electrons are released to provide an electric current. So
that all sounds very simple. And I mean it is, it's a simple pair
of reactions using pretty common, cheap and safe
chemicals. The reaction is nearly identical to a lemon
battery if you ever happen to make one of those when you're a
kid, but like with many of the technologies that I cover on
this channel, though the science is appealingly simple, the
tricky part, and the really cool part in my opinion is the
engineering. Because setting up that reaction pair in a couple
of beakers or you know, a couple of lemons would not make a
cheap, reliable, efficient, compact battery. So the actual
Redflow battery is a bit more complex. Let's take a closer
look at each component starting with the cell stacks, which
consists of layers of electrodes and separators through which the
electrolyte flows. Clelia Nelson on of Redflow's Research
Scientists is going to show those to us and explain. This is one of the electrodes. A
bit bigger, the zinc surface and the bromide surface. The
channels is where our electrolyte flows. So we have
the electrolyte coming from the pump. And after it flows
uniformly over the electrodes. Between the electrodes we have
what we call the separator it's a polymeric micro porous
membrane. And it helps keeping the some of the species we have
in the battery away from our zinc electrodes, because they
can cause self discharge of the battery. So the electrolyte
looks different depending on the charging state of the battery. It's got some zinc and some
bromine, or some form. They are the main elements for
the electrochemical reactions that we want to happen. The one
on the left is how it started out? The one on the left is the
highest state of charge of the battery. So as we produce
bromine, the organic molecule we have in the electrolyte,
captures the bromine and it settles down because it has
higher density than the water. That's the guts of the battery
where all the reactions are happening. In addition to that,
there's just some plastic tanks to hold the electrolyte and
electric pumps to move the electrolyte through the cell
stack. So some of you are likely
familiar with the concept of a flow battery. And you might be
thinking, this red flow battery is a bit unusual. And you're
right it's a hybrid flow battery and not a pure flow battery. The
basic difference is that in a pure flow battery, the actions
take place in the electrolyte at the electrodes and the ions
remain in the electrolyte suspension, whereas the Redflow
battery stores energy in the physical plating of zinc out of
the electrolyte solution onto the anode and then releases the
energy when the zinc is returned to the electrolyte. The
consequence of this is that a pure flow battery's energy and
power can be completely separated. Longer storage
duration simply comes from larger tanks. On the other hand,
in a Redflow battery energy is stored in the zinc plating on
the anode. So to get longer storage duration, you need more
surface area on your anode, but the upside is that the total
space taken up is smaller in Redflow batteries and pure flow
batteries about half that of other flow battery chemistry is
with the same energy. The efficiency of the two is similar
around 70 to 80%. And that's in the same ballpark as other long
duration energy storage options like pumped hydro or compressed
air. So that's the main components
and how the battery works. Now let's move on to some of the
practicalities. One of the most interesting aspects of Redflow
is that they have a lot of real world operation experience. Some
of their batteries have been running for eight years with up
to 2000 full depth charge and discharge cycles. The reason
that's interesting to me is that we're able to see the iterative
nature of this kind of technology development. A lot of
these kinds of videos will show technologies at the lab scale
where it's all excitement and possibilities, but to make it
off the lab bench and into the real world at a scale that can
make a difference technologies need to get cheap and reliable.
And the way they do that is through learning cycles. Design,
test, learn from your failures, and then repeat that as rapidly
as possible. So let's take a look at the research and
development that Redflow are doing. Conan Jones, Redflow's
Product Manager is going to show us the various tests that
they've got running and what design changes they've made
based on their experience from their installed systems over the
years. And this is your long duration
batteries? This is this is our long
duration battery testing. The battery on the right is our
newest generation three battery, the ZBM3, and the battery over
there is the ZBM2.5. It ramps it up and down through different
charge and discharge profiles, looks for depth of discharge,
takes it all the way down to zero, takes it all the way up to
100, runs it through linear and nonlinear testing profiles as
well as they will be tested in the real world. So this is where
we're doing some more real world testing, the long duration test
in the lab we're doing at 48 volts, which is the native
voltage of the battery. Here, we're actually connecting the
batteries to inverters. So we here we actually are creating AC
electricity out of them. And we're running them through
different types of loads. Redflow have had some of their
batteries out in the wild for years now with some at the end
of their lifetimes already or needing to be replaced for other
reasons. So what are they doing with the batteries they received
back? Is it possible to reuse and eventually recycle them? We have a complete recyclability
path and plan for the entire battery, no heavy metals, no
leads, no toxic chemicals, nothing that will break down
into a toxic chemical, we still receive batteries back that are
then disassembled and analysed either in the different labs
that we've got or in the test facilities, and then we
repurpose them. So we get separate stacks and we restack
the battery. So we increase the longevity of the battery. I love doing these in person
tours because you get a much better sense of the technology
by seeing it up close and touching it where possible. So
let's take a look at some of these batteries now to get a
sense for their size. This housing is what we're going
to call our Quadpod and it will hold four ZBM3 batteries which
will give us energy storage of 40 kilowatt hours, each battery
will be able to deliver continuously at three kilowatts,
which means that from a power rating, we could deliver 12
kilowatts, 40 kilowatt hours. So to put it in terms that
everyone understands, everyone knows the Tesla Powerwall is 12
kilowatt hours I think, a little bit deeper, but then then you
never discharged a Tesla completely So it's 12 usable? I think it's 13.4. Okay, and what'd you say this
one was? This will be 40. Okay, so it's bigger than four
Powerwalls. This will be roughly equivalent
to three or four Powerwalls. And what applications are you
expecting this for? I mean, it's not gonna fit in someone's
garage. No, it's not intended for
residential. It's possibly intended for very high end
residential, somebody who has a large estate, who might have a
house, a workshop, a games room, a pool room, a heated pool,
somebody who's got a lot of solar that they want to absorb
during the day and use at night. So this was a 16 battery module,
which was called the Pod Z. It's recently been renamed to the Pod
160, because it's 160 kilowatt hours of storage So you've got four, four, four,
four Okay, 16. So this is our Pod160. But we
will probably not produce the Pod160 again, because it had to,
it had to fit a pre-existing site. But it has led us to
develop what we will be bringing to market in the next couple of
months called our Pod200. And then instead of the power
conversion system in a cabinet, the last little bit of space is
a wider cabinet because then we can do a row of 20 circuit
breakers for the 20 batteries coming in. And that's that will
be our modular version going forward. Well, that was really cool to
get to see Redlow's facilities and learn about how the
batteries work and the development process. It's been
most of the year since I did that tour. And in the meantime,
they're moving on to bigger and bigger projects, the latest
being a two megawatt hour installation in California that
was completed in December last year. I know they've got plans
to go even bigger. And I'm really looking forward to this
next phase of the energy transition where we start to
actually build a lot of long duration energy storage instead
of just talking about it a lot like we have been for the last
few years Thanks heaps to Redflow for the
tour and their patience while I took months and months to
complete this video. If you want to help me speed up the rate
that I put out new videos whilst keeping the quality high and get
a say in which topics you think I should cover next. Then you
can join the Engineering with Rosie Patreon team at this link
and thanks to you for watching I'll see you in the next video!
