POWER May 2015 - 23

DISTRIBUTED GENERATION AND STORAGE
1. Groundbreaker. This 250-kW, 1-MWh iron-chromium redox flow battery built by EnerVault
went online in an almond grove near Turlock, Calif., last year. Source: POWER/Tom Overton
officer and co-founder of Sunnyvale, Calif.-
based EnerVault.
EnerVault has developed a grid-scale ironchromium
(Fe-Cr) redox flow battery that
went online in a demonstration pilot project
near Turlock, Calif., last July. That 250-kW,
1-MWh facility (Figure 1) is only the first
step in what could potentially be 100-MWhand-up
applications. The key advantage,
Horne said, is that the technology scales very
economically because of its modular design
and inexpensive Fe-Cr electrolyte.
Fremont, Calif.-based Imergy Power Systhing.
Because it will be able to supply both
conventional generation as well as load-shifting
and peak-shaving services, it's essentially
equivalent to a 200-MW resource.
SCE considered it for a role that would traditionally
have gone to a gas-fired combustion
turbine-based peaker plant, and in doing so
found that battery storage was more flexible
and beneficial to the system, and thus more
economic in the long run, Zahurancik said.
Zahurancik lauded SCE for doing its
homework on energy storage to understand
what it needed and what would best meet
its requirements.
" I think Edison did a good job of really
coming up with a framework to try to evaluate
what they were buying and then make sure
that they understood the process, " he said.
" They did the analytic work and came up with
a case of, 'Not only should we meet the target,
but we should be moving beyond that.' "
Lithium Leaders
GTM Research projected earlier this year that
installed non-hydro storage capacity in 2015
would triple the 61.9 MW installed in 2014,
resulting in a cumulative 2.5 GW by 2019.
Navigant Research predicts similar trends,
with 2.4 GW of distributed energy storage
by 2018. (These numbers represent mostly,
though not entirely, battery storage.) Though
a variety of battery technologies are available
(see " The Year Energy Storage Hit Its Stride "
in the May 2014 issue and " Energy Storage
Technologies Primer " at powermag.com),
two of them-lithium-ion (li-ion) and redox
flow-are dominating current installations
and projects in development.
Li-ion batteries alone accounted for 70%
of storage installations in 2014, in large part
May 2015 | POWER
because of their established technology, reliability,
and efficiency. But the very ubiquity
of li-ion batteries-which are used in everything
from consumer electronics to electric
vehicles to aerospace applications, in addition
to energy storage-has placed pressures
on global manufacturing.
Electric vehicle company Tesla aims to
address that issue with its much-discussed
" gigafactory " (shown on the cover), which
broke ground near Reno, Nev., earlier this
year, with a projected 2020 startup date. The
factory has a planned 35-GWh annual production
capacity, which is more than the total
worldwide production of li-ion batteries in
2013. The company expects that about onethird
of the production will go toward storage
applications.
Zahurancik agreed that li-ion has an advantage
in that the systems are manufactured in
a factory, which means " production capacity
can increase very, very, quickly, " he said. That
matters because the costs of earlier one-off
demonstration systems have confused some
people as to current li-ion storage costs.
" People will sometimes take something
that's a technology demo and extrapolate
the costs, when in a lot of cases these are not
baseline costs, " he noted. " What something
costs at 1 MW or 5 MW is not a good indication
of what it will cost at utility scale. "
Going with the Flow
Flow batteries, however, are attracting their
share of research and development because
of the number of different technologies that
are available. Each offers different characteristics,
but in general, flow batteries offer
better economies of scale than li-ion batteries,
according to Craig Horne, chief strategy
www.powermag.com
tems this year introduced its largest offering
yet, the ESP250. This 250-kW, 1-MWh system
uses vanadium-based redox flow technology
and is installed inside two stacked
40-foot shipping containers, one holding the
electrolyte tanks and the other holding the
stacks (Figure 2). Imergy has also developed
a proprietary process for extracting high-purity
vanadium from secondary sources such
as mining slag, oil field sludge, and fly ash.
It says this lowers its vanadium costs by 40%
compared to virgin vanadium sourced from
mining, and the firm projects that it will be
able to lower its battery costs to under $300/
kWh. The first ESP250 system is being deployed
at a data center in India.
Zinc-iron redox flow batteries are also
attracting attention because of their low
cost and abundant raw materials. Montanabased
ViZn Energy recently introduced its
GS200 design, which consists of a block
of five of its Z20 battery systems using a
single large underground electrolyte tank.
ViZn says the GS200 can deliver up to 3
MWh of energy at a price below that of
vanadium-based technology. Several Z20
systems are currently in operation, including
a facility owned by the Flathead Electric
Cooperative in Montana.
Hayward-based Primus Power offers yet
another permutation using a zinc-brominebased
design. Primus's technology is centered
around individual 72-kWh energy cells,
which can be combined to scale up capacity
as needed. Though Primus offers a 240-kW,
720-kWh containerized unit (called an EnergyPod),
it views the energy cells as its primary
product given their flexibility, Andrew
Marshall, director of product management,
told POWER. In addition, unlike traditional
redox-flow designs, Primus uses metal electrodes,
with a single-tank, single-loop electrolyte
flow without a membrane. Jonathan
Hall, Primus's vice president of engineering,
said this creates a more rugged, durable product
that can last up to 20 years.
So You Want to Buy a Battery?
For utilities and generators that are just starting
to look at battery storage as an option,
23
http://www.powermag.com http://www.powermag.com
POWER May 2015

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