Global industry ramps up as VRFB appeals to grid renewables

Solar and wind renewables can generate very cheap electricity, but like good weather, they're intermittent. To achieve a green-energy future of grids running off renewables, enormous amounts of battery storage will be needed to avoid blackouts.

The first redox-flow batteries were developed by Lawrence Thaller and his group at NASA in the 1970s as potential energy storage for solar-powered deep-space missions. They used an iron solution on the positive side and a chromium solution on the negative side, which contained no corrosive elements and was easily scalable to store sufficient amounts of solar energy indefinitely.

The iron and chromium ions, however, tended to diffuse across the membrane separating the two solutions and would cross-contaminate, a flaw that would shelve the redox battery for about a decade.

In the mid-1980s, a young chemical engineer named Maria Skyllas-Kazacos, along with her research team at the University of New South Wales (UNSW) in Sydney, studied NASA's design and demonstrated an improved redox flow battery that used vanadium on both positive and negative sides of the battery, eliminating the risk of contamination.

Called a vanadium redox flow battery (VRFB), it was safer and longer-lasting. Unfortunately, there wasn't much of a market for energy storage at the time. In the 1990s, UNSW sold the patent, which passed through the hands of several corporations – with no luck in commercializing the product – before finally expiring.

"We understood at the time we were 20 years too early," recalls Professor Skyllas-Kazacos, who is still with UNSW. "We always knew the big applications would be renewables and solar, but it took a lot longer for the market to develop than we expected."

Musk makes a move

The turning point came during the 2016-17 South Australian blackouts, amongst fierce debates on how to manage the grid.

"Elon Musk came along and said, 'I can build a battery in 100 days'. And everyone realized you can build big batteries," recalled Skyllas-Kazacos.

Lithium-ion batteries took off with Tesla gigafactories, which produced them at a relatively low cost, catapulting this technology as the default for grid energy storage.

In a lithium-ion battery, energy is stored in the solid anode and cathode. When the battery charges, lithium ions move from the cathode to the anode. As the battery powers its device, this process is reversed. However, despite steady research and engineering breakthroughs, the batteries still suffer degradation over time.

For grid-scale applications, lithium-ion batteries have further shortcomings. Battery packs capable of storing megawatt-hours require many thousands or even millions of cells, all requiring both individual and collective monitoring.

Cheaper and easier to recycle

A commercial district in Trondheim, Norway, recently made an unexpected choice in commissioning VRFB battery energy storage. The key reason for this was lower costs, according to Besart Olluri, co-founder of Bryte Batteries, which supplied the vanadium flow batteries.

At present, initial investment is relatively high, but with maintenance, the batteries can technically last forever. Compared to the two to three years of a cellphone battery or the 10- to 12-year warranty on an electric vehicle battery, a VRFB's higher capacity, longer life and less maintenance are vital to uninterrupted grid function.

"You get huge benefits both in terms of environment but also lifetime costs," said Olluri. "Even after 20 to 30 years of lifespan, you're able to easily recycle or refurbish the system to make it into a new one."

VRFBs are ideal for grid-scale applications, storing hundreds of megawatt-hours of energy that can be delivered nearly instantaneously. They may be used by large baseload power plants, which generate cheap electricity but can't speedily accommodate increases in demand during peak hours.

And as renewable sources like wind and solar farms proliferate across global power grids, VRFB batteries are increasingly becoming the support system of choice when power generation and demand fall out of sync.

"I think it's a very exciting time," said Chris Menictas, head of the Energy Storage and Refrigeration Lab at UNSW and one of Professor Skyllas-Kazacos's former students. "Large-scale batteries are required more and more and I think vanadium is one of the leading technologies."

Improved efficiency

Redox-flow batteries can be easily scaled up to megawatt-hours, sustain their performance over much longer lifetimes, and are much safer. Scaling up capacity is also easier; you simply install a bigger electrolyte tank.

A notable advancement comes from the Chinese Academy of Sciences, where a research team led by Professor Li Xianfeng from the Dalian Institute of Chemical Physics (DICP) recently presented a new generation of VFB stack technology offering improved power density at almost half the price tag. Various test results showed the stack is able to maintain energy efficiency at over 80%, running at a constant power of 30 kW and showing no decay in capacity after 100 cycles.

"The stack assembly process was improved by applying weldable, porous ionic conductive membranes that we developed," said Li. Conventional membranes used are mainly commercial perfluorosulfonic acid membranes characterized by high cost and poorer ion selectivity. "This new VFB stack technology not only maintains the high-power density of conventional stacks, but also reduces total cost by 40% compared to conventional stacks."

Laser welding allowed automation, decreased the use of sealing materials, improved ionic selectivity, and increased the capacity retention of the electrolyte with an overall reduced cost.

In layman's terms, the higher the power density is, the smaller the stack volume, resulting in lower cost under the same power output conditions. By using this stack, a 20-foot container energy storage unit module can be upgraded from 250kW to 500kW without greatly increasing the size of power units and the cost of system-supporting facilities.

"This 70kW-level stack can promote the commercialization of vanadium flow batteries," said Li.

This is encouraging for smaller footprints that still require high energy storage.

Global installations

VRFB is now being taken seriously as the next big technology for large-scale storage. Dozens of companies around the world are now manufacturing and installing megawatt-scale VRFB.

There are currently over 200 VRFB projects in multiple countries, including the U.S., Canada, Japan, Italy, Europe and South Korea, which have been deployed or are under construction, ranging from tens of megawatts all the way up to China's Dalian system (100MW/400MWh) commissioned in 2022, the largest in the world. The Dalian project is part of a multi-year Chinese plan for the nation to transition to lower energy consumption, stimulate demand for renewable energy and energy storage products and achieve net zero emissions by 2060.

The VRFB has also finally returned home, with 10 projects built and more on the way: conducting research and field demonstrations, supporting agriculture and solar farms, testing residential VRFB systems for the Australian market and, in one case, running a mine with solar power.

IGO Limited, an Australian mining company, is awaiting the installation of VSUN's standalone vanadium battery power system at its Nova nickel operation in Western Australia.

"We are now at a point where technology and cost structure are enabling powering of an entire mining operation with 100% renewable penetration," said IGO Chief Operating Officer Matt Dusci. "By supporting greater uses of renewable energy at our Nova operation, it will set a new industry benchmark in renewable energy integration and demonstrates our commitment to decarbonize our business."