Lithium-ion battery solutions currently dominate grid-level storage, but safety and scalability concerns are encouraging some players to explore more innovative options to ensure stable electricity networks.
In coming decades, as renewable energy takes over as Australia’s primary source of baseload power, batteries will play a huge part in grid stability.
While much of this infrastructure has centred on lithium-ion batteries, electric vehicle production is expected to see demand for lithium grow sevenfold this decade. Constraints on production and cost mean that industry needs to look at other sources – and quickly.
Nee Nee Ong FIEAust CPEng, co-chair of the Engineers Australia Electrical College and Senior Electrical Engineer at GHD, said that because renewable energy solutions have intermittent generation – wanting to connect to the grid while trying to retain the stability of the grid – maintaining network voltage and frequency becomes a challenge.
“Lithium batteries also present issues in terms of scalability due to their short life,” she told create. “The key issue with lithium batteries is safety, because there’s always a risk of fire and explosion due to the chemistry involved.
“There are also, historically, concerns about the limited lifecycle of lithium batteries, which adds to replacement costs and concerns about system interruption.”
In the search for alternative technologies, the quest for longer battery life carries risks around managing thermal temperatures and fire. Consideration needs to be given to the location and footprint of these batteries, government regulations and the costs of going bigger.
Scalability also greatly depends on the flexibility of the grid network and the existing infrastructure.
“Apart from making batteries safer, longer lasting, smaller and more cost effective, we need to think about alternative forms of generation that would actually be more stable to our grid system – as a centralised distribution system is more effective,” Ong said.
“We need to be able to augment the existing infrastructure of our energy system – in terms of traditional power plants and generators – and modify them to be able to integrate all these new technologies, all while ensuring that we can still keep the lights on.”
Aussie-made solutions
Queensland-based research and development firm Redflow produces the world’s smallest and most scalable commercially available zinc-bromine flow battery.
The company’s chief technology officer, Steve Hickey, said that the battery’s salt solution gives it good energy density.
“What makes our battery different is that, unlike the components in a lithium-ion battery, which are in the solid state, ours are active ingredients,” he said. “In a liquid state, that means it’s a flow battery.”
At about the size of a small bar fridge, Redflow’s battery contains 100 L of the electrolyte, and can deliver 10 kWh – around one day’s consumption for a regular household.
Redflow’s battery has 30 cells in the stack, with each cell having a nominal voltage of 1.8 V. It is compatible with the common 48 V to 60 V range, and intended to be permanently installed for energy storage rather than electric vehicles.
“Our ingredients are in the liquid state, with the salts dissolved in aqueous solution,” Hickey said. “That’s very important when you compare it with lithium-ion because water can’t catch on fire. Therefore, we do not have the same thermal runaway problem that lithium-ion batteries have.”
Charging the battery sees zinc dissolved as an ionic solution in the water, which gets plated out electrochemically, much like a galvanising process.
In the other half cell, the bromide converts to bromine and a sequestering agent in the solution turns that bromine into an ionic liquid that sits in the bottom of the tank.
That, in turn, stores the energy in the battery. When the two parts are brought together again, the energy is used, with zinc dissolving back into the electrolyte.
Hickey said that vanadium and iron-flow, key competitors to zinc, require systems two to three times bigger to have the same energy capacity. What initially started as a domestic battery has evolved to be more suited to infrastructure, such as telecom installations and energy security.
Researchers believe that the global zinc-bromine market will increase from around $13 billion in 2023 to around $70 billion by 2032.
Hickey said that Redflow batteries are currently operating at about 250 sites around the world, and the firm has increased its manufacturing capacity to larger-scale projects, including the 2020 opening of a factory in Thailand that is capable of around 40 MWh of production per year.
Two key projects highlight how zinc-bromine batteries are scalable for large projects, and why Redflow believes that it can continue to be scaled up in future.
The first is a 200-battery installation for two megawatt hours at a waste-to-energy facility in California, about an hour outside of Los Angeles, which takes food scraps and converts them into natural gas to be burned in the system. The plant runs on gas generators, with batteries as a support.
Closer to home, Redflow is working with Energy Queensland on a four megawatt hour system near Ipswich, which will house around 400 batteries.
Located in a suburb with a lot of rooftop solar, it will store the excess power from those domestic panels and then release it for the evening peak demand.
“We are scaling up to building installations with thousands of these batteries,” Hickey said. “We’ve also developed a technology that we call ‘hibernation’, where we can charge our batteries up in one day and leave them holding that status indefinitely.
“This means we can take energy collected in January and enjoy it in March, if we wish. That’s a very flexible capability and very important for the upcoming energy transition.”
Salt solution
While Redflow is pioneering in the flow space, Western Australia’s Altech Batteries is commercialising its Cerenergy sodium chloride solid-state battery for the grid storage market in a joint venture based on research from the Fraunhofer IKTS institute in Germany.
A fire- and explosion-proof alternative to lithium-ion, the sodium chloride technology operates in extreme hot and cold temperatures. Made with table salt and nickel powder metal, Altech does not use lithium, copper, graphite or cobalt – meaning it is insulated from fluctuating global element prices and supply chain issues.
“The life of our batteries is about 15 years – so nearly double the life of the lithium-ion battery,” Iggy Tan, Altech’s managing director, explained. “The reason for that is that we don’t have a liquid electrolyte like the lithium-ion battery; we actually have a solid-state technology.”
Tan said that the Fraunhofer Institute has been working on this technology for nearly a decade, spending €35 million (A$57.6 million) in development. He estimates that the sodium battery will be about 40 per cent cheaper than lithium-ion batteries.
Space-age technology
American nickel-hydrogen battery manufacturer EnerVenue is building a million-square foot gigafactory in Kentucky to scale up technology that has been successfully deployed for about 30 years in the US space program.
“It’s the most durable battery technology ever conceived,” CEO Jorg Heinemann told create. “It performs electrically much like lithium-ion batteries, meaning we have a very high round trip efficiency.”
With fast charging capabilities and performance that is almost impervious to outside temperature, Heinemann said nickel-hydrogen is the “ideal battery for anything stationary”.
It generally can be overcharged without risk of fire or explosion, can be over-discharged – drained all the way to zero – and doesn’t require any maintenance.
“Unlike lithium-ion – or any other battery for that matter – our batteries effectively last forever,” Heinemann said. “They have a 30,000 cycle life and they’re incredibly durable, not just in second life, but in terms of how you can use them.”
The most common use case for EnerVenue products is a solar-plus storage-plus energy arbitrage, Heinemann said.
Many have a “two hump” charge, where there are both morning and evening peaks. This requires cycling the battery twice – one of the cost benefits of nickel-hydrogen over lithium.
“The operations and maintenance component tends to be a significant driver for the economic value case for battery applications,” Heinemann said.
“Power applications are typically up to a third of the levelised cost. The amortised operations and maintenance expense of having a battery that you don’t ever have to touch is a huge advantage.”
The battery cells are tube shaped, about 1800 mm long and 150 mm in diameter. Inside the tubes, a sealed pressure vessel contains an electrode stack.
Applying charge to the ends, there’s a third tank with a large-scale, 30 V battery. On the inside, a catalytic reaction generates hydrogen, a process known as hydrogen evolution.
As the battery charges, the hydrogen pressure builds to a peak of about five per cent of a typical hydrogen fuel cell. Then, as it discharges, that hydrogen recombines into water to create a hydrogen-oxidation reaction.
“There’s no dendrite build-up – nothing that causes accelerated degradation,” Heinemann said. “That’s fundamentally different from any other chemical or mechanical battery.”
EnerVenue believes it can do everything that lithium-ion does but better, all while being safer and more versatile.
The simplicity of the device means that it requires no air conditioning or fire suppression systems, and the batteries can be stacked high.
“In terms of cost, we’re quite competitive,” Heinemann said. “We have a unique value that customers are willing to pay for. Think of it as a price premium relative to lithium.”
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