Why Isn’t This Revolutionary Battery Everywhere?

Vanadium redox flow batteries are hitting the bigtime, and I mean big. One of the biggest Battery Energy Storage Systems (BESSs) ever is a vanadium redox flow battery that just came online in China, with an even bigger one to come in Switzerland. And there’s even more on the way in other countries too. But it raises a couple of questions: “why now,” and “why are they suddenly everywhere but North America?”

This is a vanadium redox flow battery (VRFB). They play nice with solar and this one can fit in your garage … and I wish I had one in mine. Flow batteries scale-up really well too. This one here is a 51 megawatt facility in Hokkaido, Japan, and it was the biggest in the world when it opened in 2022. However, at the end of 2024 it has been dwarfed by Rongke Power’s own Xinhua Ushi Energy Storage Project in Xinjiang, northwest China. At 175 megawatts (MW) and 700 megawatt-hours (MWh) of storage, it’s currently the largest battery storage system of its kind.^{1 2}

But soon, an even bigger VRFB will be online. Rongke’s monster is set to be overshadowed by a VRFB starting construction this year in Switzerland. Part of a massive telecom facility, this VRFB clocks in at 500 MW and 1.2 gigawatt-hours of storage.³⁴This is a pretty meteoric rise for vanadium battery tech. So how does it work? Where did this tech come from? And maybe most importantly, why has it exploded in popularity the last few years?

VRFB’s Journey

Broadly speaking, redox flow batteries work by having two large tanks, one with a positively charged electrolyte solution and one with a negatively charged solution. Both these tanks are connected to a central chamber or “stack,” and when we pump our electrolyte solution through the stack, we get an ion exchange, or redox effect as one side _re_duces and the other _ox_idizes. When charging, we put electricity into the battery and this causes ions to move from the positive side of the membrane to the negative side. The redox process is reversible, so the stored energy is released as ions and electrons return to their original states, generating a usable electric current.⁵

Vanadium wasn’t the OG flow battery, though. That honor goes to the zinc flow battery, patented all the way back in 1879.⁶ I’ve got a video on that if you’re interested. Not a whole lot was done with it until the energy crisis saw a surge of interest in renewables and alternative battery technologies. NASA experimented with redox flow batteries in general,⁷ but its efforts weren’t very successful.⁸ Others weren’t having much luck either, because we just didn’t have good enough membrane tech or electrolyte solutions.

Then, in the 1980s, researchers at the University of New South Wales (UNSW) in Australia successfully demonstrated vanadium redox flow chemistry using vanadium dissolved in sulfuric acid. And just like that, we had a promising electrolyte. There was another boom of interest, and the university patented the tech and licensed it to a few companies.⁸

What makes vanadium interesting? It’s a bit of a weirdo. It likes to both give and receive ions, giving multiple charge or oxidation states.⁸ In fact, vanadium batteries rely on vanadium having not one, not two, but four different possible charge or oxidation states.⁹ Two of them are more positive, and two of them are more negative.¹⁰ Chemically, this is very strange, and means that we can use vanadium for both the positive and negative sides of the flow battery. Most flow batteries require two distinct solutions, which can result in them bleeding over the membrane and hampering the battery’s efficiency and lifespan.⁸ Vanadium doesn’t have to worry about that. I also imagine it makes the supply chain a little easier if you have to source one less electrolyte solution.

Still, these batteries remained pretty niche and underutilized for several years. But 2006 would see several VRFB patents expire, and plenty of organizations spent serious time and money developing VRFBs¹¹. That same year, the U.S. Department of Energy’s Pacific Northwest National Laboratory started R&D on their VRFB formula. By 2012, this led to a new-and-improved vanadium-based electrolyte formulation that was twice as powerful as similar mixtures.¹² Soon, VRFB technology made its way from the lab to real life, aided by the growth of solar and wind power. Adoption was slow initially, but with companies like Rongke Power announcing some big plans for the technology, the race was on.

So what has Rongke Power done with VRFBs? As I mentioned earlier…a lot. At 175 MW and 700 MWh, the company’s Xinjiang facility is the biggest VRFB on the planet, which also makes it the biggest flow battery on the planet.¹³ That’s at least until that Swiss facility opens up next year, but I’ll get to that in a moment. This isn’t Rongke Power’s only big VRFB. The company is behind another, smaller but still huge 100MW/400MWh system. Back in June 2024, Rongke reported that the Dalian facility completed the world’s first black start test of a large-scale thermal power system. A “black start” involves restoring power to the grid following a total blackout. It’s an important safety measure that demonstrates that the VRFB can provide energy even when total disaster strikes.^{1 14}

Why is China investing so much in giant VRFBs? Well, as Uncle Ben once said, with green power comes green responsibility…and that responsibility is storage. China aims to be the world leader in renewable energy.¹⁵

Part of this drive means constructing massive energy storage facilities to work in tandem with massive renewable energy generators. As we’ve discussed in previous videos, a lot of emissions-free power has the downside of being intermittent. The sun isn’t always shining, the wind isn’t always blowing, y’know the deal.

Before Rongke Power, the biggest VRFB could be found in Japan’s Hokkaido region. Hokkaido gets a ton of wind, so naturally the Hokkaido Electric Power Network (HEPCO) has invested in a robust wind turbine system.¹⁶ But HEPCO wondered what was the best way to store all that wind power for later? Ultimately, it settled on Sumitomo Electric Industries and a massive VRFB system.

At 51 MW, this setup uses 130, 10,000-gallon, vanadium redox tanks. That’s more than enough VRFBs to power 27,000 Japanese homes for four hours.⁵ The VRFBs here are engineered to store energy for around four hours of use. That’s about what you’re going to get from grid-scale lithium energy storage systems, though Sumitomo Electric says it expects future projects will aim to double that duration to eight to 10 hours. That would be a big deal, as that’s what you’d need to cover for solar panels during the night or to give wind turbines a lot of wiggle room between gusts.⁵The project has been so successful that Sumitomo has gone on to install similar VRFBs systems all over the world, including in Belgium, Australia, Morocco, and California.⁵

So, let’s talk about the soon-to-be biggest VRFB facility. Swiss telecommunications company FlexBase is building a 20,000 square meter data center in Laufenburg, Switzerland. Data centers take a lot of energy, so FlexBase wants to offset that with tons of green energy and green energy storage. To that end, the company is set to begin construction on a 500 MW/1.2GWh VRFB, the biggest in the world.⁴ The campus will generate at least some of its own power with a 8,400 square meter photovoltaic system. FlexBase is also planning to use its waste heat as part of Laufenberg’s the district heating network.¹⁷

Laufenberg was chosen as the home for this facility for a reason. The town is right across the Rhine river from Germany, and also sits near the original connection point for the electricity grids of France, Germany, and Switzerland. This network node was decommissioned in 1958, but the location is still critical for the distribution of green electricity in Europe’s interconnected grid.¹⁸

But, as promising as they may be, flow batteries are just as vulnerable to economics as any other new technology. Back in March 2024, Horizon also announced it was preparing to test Redflow’s zinc-bromide flow battery, but the project didn’t make it very far.¹⁹ By October 2024, Redflow went belly-up.²⁰ It’s a painful example of how precarious the greentech business can be.

Why VRFB Batteries?

Clearly, VRFB tech works great for gridscale storage, but why? We’ve covered this previously so I’ll keep it brief. Flow batteries are great at large scale projects primarily because they’re so easy to scale up. Need more juice? Get bigger tanks.⁸ You might be sitting there saying “no duh,” but stuff in the electro-chemical world is rarely that simple. Look at some of the other emerging battery technologies, and the simplicity of scaling up a VRFB seems almost too good to be true. If you want to adjust the capacity of most other battery systems, lithium included, you’re just buying additional batteries. You want to double the capacity, you have to double the number of battery packs. Power output and energy storage scale together. VRFBs can scale those separately between the tanks (the storage) and the stack (the power).

VRFBs, of course, have their own perks aside from being flow batteries. We’ve already mentioned that vanadium is a strange substance with four different oxidation states, which makes it really convenient and efficient in a redox battery.²¹ That’s the big one, but there’s other benefits, too. The electrolyte solution isn’t flammable, and isn’t sensitive to extreme temperature fluctuations. That kind of safety is important, especially for wildfire-prone regions.

Another small but useful perk is that VRFBs can stay discharged for as long as you need them to without degrading. Their simple chemical formulas and benign chemical reactions give them extremely long lifespans. We’re talking upwards of 15,000-20,000 cycles⁸. By some accounts, that’s five times longer than lithium.²² Sumito claims that its VRFB will last at least 20 years.⁵

That all helps to contribute to their low LCOE, or Levelized Cost of Energy. Generally, VRFBs are going to have cheaper LCOEs than lithium systems.²³ When a VRFB does finally kick the bucket, most of the vanadium can be recycled into a new VRFB. US Vanadium demonstrated its ability to recycle 97% of the electrolyte from a decommissioned VRFB.²⁴ Sumitomo took spent VRFB electrolyte from a battery that was in service for a decade, then processed it and repurposed it for use in a different VRFB. The company says it’s been working effectively in its new home since 2012.²⁵ To be fair, these examples are isolated showcases, far from a fully functional VRFB recycling system, but they do highlight the recycling potential of vanadium.

What About the Drawbacks?

Of course, vanadium batteries aren’t without their drawbacks. Let’s just get the most obvious one out of the way first: They’re big. That’s great for grid scale storage, a potential option for residential storage, but not something you’re not gonna see inside an EV or laptop.

VRFBs also have a relatively poor round-trip efficiency (RTE). That’s a measure of how much electricity you can store in a battery and then actually pull out later. When VRFB cells are small, they have a pretty good RTE of 85–90%. But once you get into kilowatt-scale stuff that number drops to 57–75%, due to hydraulic losses and shunt currents.²⁶ Not ideal for a technology that we want to use in massive energy storage systems.

As for the question of why we aren’t seeing a lot of vanadium batteries here in the US, vanadium has a serious supply chain bottleneck. 75% of the global vanadium supplies comes to us as a byproduct from just 10 steel mills in China and Russia. Other countries like the United States and Australia produce some vanadium, but not enough. Vanadium is often found in iron ores used in steelmaking. With steel being easily recyclable, little vanadium is produced in the US. If we want to build massive VRFB facilities, like the kind we’ve been talking about today, we may need to alternate sources of vanadium.⁵ Then again, there are some significant vanadium deposits in the United States that are largely untapped.²⁷

This plays into another VRFB issue: upfront cost. Vanadium is twice as expensive as lithium.⁵ That can be offset by their long lifespan and their low cost of maintenance. However, the high initial cost and their new-ness on the market make VRFBs an expensive risk to a lot of investors. And again, massive facilities will take massive amounts of vanadium. Anyone out there willing to offer a Costco-style bulk discount?

These are some of the reasons why, despite vanadium’s strengths, you might choose other flow battery chemistries, like zinc-bromide or hydrogen-bromine. If vanadium is the problem then just ditch vanadium, right? Of course, these batteries have their own issues, but that’s a topic for another video. Like maybe this one here.

Where does that leave VRFBs on the technological readiness level?²⁸ A high score for sure, maybe as far as a 9. They’re out there and working right now, providing hundreds of megawatts to people across the globe. It’s proven technology with a well-defined niche.

As we continue to decarbonize, it’s possible that VRFBs will become more popular. It’s pretty heartening to see some of the massive facilities already working, and even bigger ones are on the way. Still, I want to caution against unbridled optimism. Despite the successes of VRFBs in China and Japan, there’s no guarantee that all these announced, new facilities will complete construction. Still, these early, full-scale successes are pretty exciting.