Are flow batteries the future of home energy storage? Q&A with Redflow’s Simon Hackett

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RedFlow’s ZCell is one of the most is one of the most in-demand battery storage products on the Australian market; it also stands out for being one of the only ‘flow batteries‘ currently available. Solar Choice had the opportunity to catch up with RedFlow CEO Simon Hackett about the role of flow batteries (and the ZCell) in Australia’s energy transformation, in the process discussing how the ZCell compares to the vast array of lithium-based batteries sweeping the market. Our conversation is included below.

Q: RedFlow’s ZCell is the first flow battery to hit the residential market in Australia. How do flow batteries – in particular your zinc-bromine flow batteries – compare to competitors like lithium and lead batteries for home energy storage applications?

Redflow Limited has developed the world’s smallest zinc-bromine flow battery, a purpose-designed energy storage system without the overhead or many of the degradation and safety problems that can impact the performance of lithium-based or lead-acid batteries.

Redflow’s new battery, ZCell, is a breakthrough residential energy storage system that includes a battery made from easily recyclable or reusable components. ZCell allows people to ‘timeshift’ solar power from day to night, store off-peak power for peak demand periods and support off-grid systems.

ZCell is a unique battery that loves to be fully charged and discharged daily. ZCell comes with an energy output capacity of 10 kilowatt hours (kWh) and can discharge 100 per cent of this energy on a daily basis without any damage to the battery – so the full 10 kWh is repeatedly usable.

In contrast, a lithium ion battery requires reserved capacity to protect against fully charging or fully discharging the underlying storage cells, as these activities can damage or destroy such a battery.

Lithium-based chemistries also lose capacity with age, often far ahead of the claimed lifetime of the battery concerned (as anyone who owns a laptop or a smartphone will attest). By contrast, ZCell is designed to deliver its 10 kWh energy output capacity throughout the warranted 10-year life of the battery electrode stack. Other ZCell benefits include:

  • Greater safety inherent in ZCell’s flow battery design: Mechanical damage does not risk explosion and the battery is not prone to ‘thermal runaway’ (industry code for ‘bursting into flames!’). Indeed, ZCell’s bromine-based electrolyte is intrinsically fire retardant.
  • Robust performance in even hot and demanding remote locations without the need for external cooling; and
  • Recyclable or reusable: Most components, including plastic, aluminium, steel and ZCell’s electrolyte, are recyclable or reusable.

ZCell’s easy integration with a variety of popular and cost-effective 48-volt industry inverter/chargers and the preservation of output capacity makes them cost-competitive with current lithium-based battery energy systems on a fully installed system cost-per-kWh basis.

[You can check out how the ZCell compares to other battery products on the Australian market using Solar Choice’s Battery Storage Product Performance Comparison Tool.]

The bottom line is that ZCell is competitive with lithium-based and lead-acid batteries in terms of price, performance and lifetime capacity while offering unique technical advantages.

simon-hackett-with-zcell-battery-enclosure-02-1mbQ: Will flow batteries eventually become the battery of choice for households?

That’s up to consumers to decide. We expect a variety of battery systems to become popular in households in what is now a rapidly expanding market. For ZCell to succeed, lithium-based batteries don’t have to lose!  For discerning consumers who require a powerful, long-life battery with unique performance and safety features, then ZCell is an attractive option and we believe we will be very successful with deploying it in Australia and around the world.

Q: Generally speaking, what are the biggest downsides to flow batteries?

While flow batteries are based on a long-proven technology, ZCell is new to the market, so it will take time to build up a strong, experience-based referral pipeline. That is one of the reasons we are taking our time to build an Australian installer channel, maintaining a strong focus on manufacturing quality and ensuring we take on board feedback from our customers. Our goal is to do it once and do it right rather than to simply chase after low-hanging fruit. We are in this market for the long haul.

Q: We recently took a look at Google search trends for battery storage products. Next to Tesla’s Powerwall, Redflow’s ZCell seems to have made the biggest splash in the public consciousness. How are you finding interest levels, and what proportion of interested parties seem likely to actually go ahead and install a ZCell at home?

Redflow has received an extraordinary level of interest since we launched ZCell in Australia in March this year, with more than 38,000 unique visitors to the www.zcell.com website since it was launched at the end of March. To date, more than 1,200 people from around Australia have directly expressed interest in buying ZCell-based energy systems.

I think that’s because consumers are looking for an alternative to the “you can have any battery you like as long as it’s lithium” approach taken by the rest of the sector. ZCell’s zinc-bromine chemistry offers clear and compelling advantages over lithium-based batteries.

Q: Describe the perfect home for a ZCell – who would get the most benefit out of installing one right now?

There are multiple use-cases for ZCell, so its “perfect home” is any place that it solves energy storage and delivery challenges. For example, generous solar feed-in tariffs are disappearing this year from states including NSW, so people with solar panels may decide they are better off installing a battery so they can self-consume their solar energy rather than sell it cheap to the grid and then buy it back when it’s expensive. As well as reducing grid energy consumption, they gain the advantage of uninterrupted power supply, a business continuity benefit that will also appeal to businesses suffering unreliable power supplies. The good news for these customers is that ZCell will maintain its energy storage capacity over time rather than lose storage capacity, as occurs with lithium-ion and lead-acid batteries.

ZCell is also a great option for off-grid applications because of its sustained energy storage capacity over long periods and its ability to be switched off in any state of charge – anywhere from completely full to completely empty – and left for any period of time without losing stored energy or damaging the battery. Being left idle (and worse, discharged) for extended periods will damage other battery types – but these scenarios are harmless for ZCell.

As well as domestic and business applications, we believe Redflow’s Zinc Bromide Module (ZBM) flow batteries offer enormous advantages as grid-scale energy storage for electricity suppliers. We already have a solution available in our LSB (Large Scale Battery), a container-size unit that holds as many as 60 flow batteries with energy storage of 600 kWh. Deploying these LSBs, which function as “virtual batteries”, holds the potential to transform “intermittent” energy sources such as wind and solar into 24×7 energy supplies that can replace baseload generators powered by fossil fuel.

Q: Home battery storage is still quite pricey – the ZCell is no exception (although Redflow is admirably up-front about pricing). We’re clearly in the ‘early adopter’ phase of the market right now. Where do you see prices going in the near future, and are flow batteries on the same downwards trajectory as lithium? Middle-term future? Long-term future?

The total installed price for ZCell-based energy storage systems is set by installers rather than by Redflow itself. However, that said, Redflow’s battery technology is just at the start of its price-down curve, unlike lithium-based batteries which have been driving down costs since the start of the 1990s. The battle for Redflow hasn’t been to make our batteries cheap, but to make them reliable and manufacturable. We have now cracked that nut, which is why we can look forward to delivering the cost downs in future.

We have started with early adopters, whose motivations are aspirational as well as cost-driven. There is no shortage of early adopters at the current pricing.

Q: Anything else you’d like to add?

ZCell is the ‘missing link’ in the renewable energy revolution, letting you timeshift energy from when your solar panels harvest it to when you need it. ZCell delivers Redflow’s proven, industrial-strength ZBM2 battery in an attractive, easy-to-install enclosure for your home energy storage system. Purpose-built for stationary energy storage applications, ZCell is designed to work hard every day to store energy when the sun shines and then supply it when it’s needed. ZCell raises the bar in home energy storage by offering large energy storage capacity, inherent safety and robust performance.