The Knox Children and Family Centres at Wantirna South, which has embraced Redflow's technology.

Brisbane-based Redflow delivered a powerful 172 per cent growth rate with technology that’s electrifying the built environment sector. South Australian Simon Hackett has noticed – and so have a few other people in places like New York.

In the built environment sector, interest in storing renewable energy is surging. But large lithium batteries pose a number of issues for building owners, ranging from long-term reliability to the risks of fires caused by thermal runaway.

An Australian company is leading the way in deploying a scalable energy storage system that overcomes many of the challenges of lithium – and business is booming. 

To date, Brisbane-based Redflow has installed more than 200 of its bar-fridge sized batteries, which are based on a zinc bromine flow technology that’s safer and more reliable than lithium.

The company’s growth has attracted the interest of a number of high profile investors, including top South Australian tech entrepreneur Simon Hackett, who is best known as the founder of internet company Internode, which he sold to iiNet in December 2011 for $105 million.

“Where lithium is a sprinter, we’re more like a marathon runner. When you want to effectively and efficiently shift energy for use over longer medium to longer term duration, that’s really where flow batteries have a unique value proposition.”

REdflow CEO Tim Harris

In its most recent half-year results, the ASX-listed firm reported a 172 per cent year-on-year surge in revenue to $1.2 million (covering the six months ending 31 December 2021).

“It’s still a small number compared to the overall market opportunity for us. But we’re pretty excited about some of the growth opportunities that we’re seeing for us in the market at the moment,” Redflow chief executive Tim Harris told The Fifth Estate.

Redlow has around 50 staff at its Brisbane headquarters, a small software development centre in Adelaide, and a wholly-owned manufacturing facility in Thailand. It has recently started hiring staff in the US to support its international expansion.

In December 2021, Redflow finished installing a grid-scale energy storage system in California, at clean energy giant Anaergia’s Rialto bioenergy facility. The system features 192 batteries, which can store up to 2 megawatt hours of energy.

Since then, Redflow has signed a non-binding letter of intent with Anaergia’s subsidiary SoCal Biomethane for a 5.5–6.0MWh system.

“I was in the US in January, and there are huge opportunities for companies like Redflow to go in and target those markets, and really show the rest of the world how Australian developed technology can lead the world,” Mr Harris said.

Anaergia’s battery pack.

A powerful solution for sustainable buildings

For building owners, managers, builders and developers, one of the most attractive features of Redflow’s batteries is that they are relatively small, scalable and modular.

“One of the things that we’ve done is that we have the smallest flow battery on the market, which is a 10 kilowatt hour battery. If you’re looking at the size of the battery, it’s about the size of a small bar fridge,” Mr Harris said.

“The fact that they’re modular means they can be put into basements or alongside other buildings in a very scalable way. When you want to scale up, you just add more of [them] to a system, as we’ve done in a number of different commercial and industrial deployments.”

The zinc bromine flow technology used in Redflow’s batteries give it a number of powerful performance advantages over lithium, including being able to hold a charge over a longer period of time.

Perhaps the biggest advantage for flow batteries is safety. At its simplest, Redflow’s batteries work by flowing a non-combustible zinc bromide electrolyte solution between tanks, rather than adding an electrical current to a potentially flammable material like lithium.

“A simple analogy is that where lithium is a sprinter, we’re more like a marathon runner. When you want to effectively and efficiently shift energy for use over longer medium to longer term duration, that’s really where flow batteries have a unique value proposition,” Mr Harris said.

“You can continue to do that without any loss of capacity or performance over time. So you can go 100 per cent fully charged, get to zero, and then go back up again.

“Whereas lithium batteries have a reserve level and, if you go below that, you permanently damage the battery pretty quickly.”

Safety first is pretty attractive

But perhaps its biggest advantage for flow batteries is safety. 

At its simplest, Redflow’s batteries work by flowing a non-combustible zinc bromide electrolyte solution between tanks, rather than adding an electrical current to a potentially flammable material like lithium.

While the battery is being charged, pumps push that electrolyte liquid through an electrode stack, which causes the zinc to be plated as a solid metal. To discharge the battery, the pumps are run again to dissolve the zinc back into the electrolyte solution.

“We don’t have a risk of thermal runaway and we don’t use any flammable materials. We have high tolerance for high ambient temperatures without the need for external cooling. So in Australian conditions, we don’t need active air or water cooling. 

A Redflow battery pack from the Knox Children and Family Centres at Wantirna South.

Making greener buildings child’s play

This combination of reliability, safety and scalability means Redflow batteries are particularly well suited for a range of commercial uses, including childcare and medical facilities.

For example, two state-of-the-art children and family centres in Melbourne’s outer eastern suburbs eliminated three-quarters of their energy costs during winter with insulation, solar panels and Redflow batteries.

Designed by K20 Architecture, the Knox Children and Family Centres at Wantirna South and Bayswater, opened in 2019, each have 100 kilowatts of photovoltaic solar panels and 18 Redflow batteries, storing as much as 180 kilowatt hours of energy at each site. 

“The latest stats that we had is that those renewable energy deployments eliminated about three quarters of their energy costs during winter,” Mr Harris said. As a result, the Knox City Council saves around $220,000-$240,000 per year on its energy bills across both centres.

Meanwhile, during a recent grid blackout, Redflow batteries were able to keep vital Covid vaccines refrigerated at a medical clinic in the Melbourne suburb of Doncaster East. 

“All around this medical centre, there were a lot of Covid vaccines that were wasted, whereas our batteries were able to sustain energy to that medical centre and save those Covid vaccines.”

High-voltage global growth

While Redflow’s international growth is being led by large grid-scale deployments, the company’s technology continues to spark the interest of the sustainable building sector at home and abroad. 

“In New York at the moment, we’re speaking to big property companies that are committed to a energy storage solution, but are not really keen to put lithium into their buildings,” Mr Harris said.

“When they’ve come across our technology they’re very interested, so we think there’s lots of opportunity for us in the building industry and deployment into large buildings as well.”

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  1. The reality is we should be using the right battery technology for the job given the amount of resources required to electrify to worlds energy requirements. Keep lightweight, high density lithium batteries for mobile devices and cars, while using the larger and safer flow batteries for home and grid installations.