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RESEARCh ANd dEvELOpMENT

Batteries taking charge

The ability to affordably store

energy in large quantities for both

residential and grid applications

is set to redefine energy consumption,

production and grid operation. With

batteries set to become a requisite part of

residential power systems, it should come as

no surprise that development in the energy

storage sector has gone into overdrive.

Lithium-ion (Li-Ion) batteries are the

current forerunners in this booming

industry, and with their high energy density

and compact footprint it’s easy to see

why. Indeed, a host of lithium alternatives

to Tesla’s now famous Powerwall are

beginning to come out of the woodwork.

Advancements in lithium battery

technology are also progressing with US

body, the National Institute of Standards

and Technology (NIST), University of

Arizona and Seoul National University

jointly developing an inexpensive method

for fabricating Lithium-Sulphur batteries.

Through a process coined ‘inverse

vulcanisation’ researchers have produced

a stable plasticised sulphur cathode that is

cheap (sulphur is a petroleum bi-product)

and easy to produce. The resulting battery

was touted to retain over 50% of its

capacity after 500 cycles.

Their ability to deliver in power intensive

situations means lithium batteries can

perform well in a range of applications,

but the alkali metal’s inherent instability

and the battery’s consequential

incendiary potential will always dissuade a

considerable portion of the market.

To fill this gap there is a host of emerging

battery chemistries and technologies that

have the potential to deliver some very

stiff competition to lithium and make

the energy storage market extremely

competitive in the near future.

REdfLOw’S ZBM

A relatively small, modular zinc-bromine

flow battery that can also be containerised

to form large scale storage systems

has been developed by Brisbane-based

company Redflow. The batteries, or

zinc-bromide modules (ZBMs), range

from 8–11kWh and have a footprint of

just 0.34m².

Flow batteries operate by continuously

pumping an electrolyte between a

storage compartment and a reaction

chamber containing the electrodes. This

action means flow batteries contain

more moving parts than most other

batteries and while this can be seen

as a disadvantage, the separation of

compartments also allows for the

replacement of the electrode stack while

retaining the battery’s other elements.

The nominal 48V batteries have a

100% depth of discharge and operate

at near linear voltage and current levels

across all charge states, making them well

The fervour surrounding energy storage devices is driving significant developments in battery chemistry and technology, causing a diverse marketplace to emerge. Jacob Harris explains.

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suited to energy applications as opposed

to power applications.

While the company’s key target market

is telecommunications base transceiver

sites, Redflow also focuses on transmission

and distribution deferral over smart grids

and micro grids, renewables integration, on

and off grid remote power and residential

energy storage.

The batteries can be kept at low or zero

state of charge for long periods of time

without degradation and can use their full

capacity for deep day-in day-out cycling.

ZBMs can also be stored uncharged and

have an indefinite shelf life.

“We have a longer base life than Li-Ion

and when factoring in the ZBM’s capacity

for 100% depth of discharge and its

indefinite shelf life, Redflow’s battery

life can be seen to significantly increase.

Our ZBM3 (11kWh) has an expected

life of more than 44,000kWh, and this

can be extended further with a stack

replacement,” says Redflow’s marketing

manager Sciobhan Leahy.

ZBMs are built from a commonly

sourced plastic and contain no rare earth

elements. Their electrolyte (a water

based solution of zinc-bromide salt) is fire

retardant and because of the separation

of the stack and tank there is no chance of

thermal runaway.

ZBMs are managed by an on-board

Module Management System (MMS) that

controls battery operations while providing

access to battery status, real-time data,

event logs, warnings and alarms. This

allows the battery to self-manage and

protect against potential risks.

Ambri’s liquid metAl bAttery

American company Ambri is in the

process of fine tuning a liquid metal

battery. Originally developed by MIT

professor Don Sadoway, the technology is

touted to fundamentally change the way

power grids are operated. Unfortunately,

dates for the first commercial sales have

recently been pushed back due to an

issue with one of the battery’s seals, but

the company is still progressing with

development – albeit at a reduced pace.

The battery’s cells are made of three

simple components, a salt electrolyte

which separates two metal (electrode)

layers of magnesium (Mg) and antimony

(Sb). Because of their different densities

these components naturally form three

layers when in a liquid state. As the

battery discharges, Mg electrons move

across the electrolyte to form an Mg-Sb

alloy, when the battery is recharged the

metals separate again and return to their

original compositions.

Because the battery is all liquid, the

electrodes will not degrade in the same

way as their solid counterparts. This means

the battery could potentially last many

years without losing much of its storage

capacity. The batteries are also incredibly

scalable and can range in size from 100kWh

to hundreds of mWhs.

The cells are housed in steel containers

and are assembled in systems using

basic components such as steel racking.

Because of this, Ambri’s manufacturing

strategy involves steel workers on a

production line that is similar to an

aluminium smelter. This relatively

simple manufacturing process and

the technology’s use of cheap, earth

abundant materials, means the batteries

promise to be extremely affordable to

build and maintain.

Aquion energy’s Aqueous

hybrid ion bAttery

Commercial shipments of Aquion

Energy’s AHI batteries began in mid-

2014 and are rapidly increasing because,

according to Aquion’s VP of product

management Matthew Maroon,

they satisfy several unmet market

requirements.

Being saltwater batteries that use no

heavy metals, they are a clean, non-

toxic energy storage solution based

on abundant, low-cost materials. AHI

batteries are modular and scalable for

various power/energy ratio applications

up to mW scale and are easily

manufactured, providing economical,

long-duration storage for high-energy

applications such as renewable energy

storage and time shifting.

“AHI batteries are optimised for

daily deep cycling (defined as 4 to 20+

hour charge and discharge cycles) for

residential solar. Being adept at long

duration cycling and because they’re

not damaged by long stands at partial

state of charge, they are high performing

under solar cycling profiles and are the

cleanest and safest storage solution

available. In fact, Aquion batteries are

the only ones that are Cradle-to-Cradle

certified and we’ve found that their

inherent safety really resonates with

customers,” says Matthew.

As the energy storage market grows,

we can expect new innovations in battery

technology to come to light increasingly

frequently. There is room for multiple

players in battery manufacturing as

different battery chemistries will play a role

in meeting the needs of different customer

types and applications.

development in the energy storage sector has gone

into overdrive.