Industry insight: VRFB will fail to take off claims ZnBr flow battery VP

Industry insight: VRFB will fail to take off claims ZnBr flow battery VP

Industry insight: VRFB will fail to take off claims ZnBr flow battery VP Energy Storage Journal


Paul Kreiner, VP Primus Power

Paul Kreiner, a former Tesla engineer and vice president of engineering at zinc bromine flow battery firm Primus Power, told ESJB this week that vanadium redox batteries will never match lithium ion because of costs and an unclear path to commercialization.

Kreiner said that vanadium flow batteries will fail in its attempts to be the next generation battery, and may never be able to compete against lithium ion.

Kreiner said: “I suspect that vanadium flow batteries have not seen the commercial success of lithium ion batteries because of cost concerns.

“As lithium ion prices fall, I’m not sure vanadium will every really take off commercially. Vanadium has played a key role paving the way for flow, but as people look to the next generation of battery technology, there’s not a clear path for it to compete with lithium ion.

“Any storage system will have to have a very aggressive cost roadmap and cost itself significantly lower than lithium ion. Longevity is important, but if the battery were cheaper to replace it wouldn’t be such a big deal.”

His comments were made during a discussion on zinc bromine technology, and the place flow batteries have in the energy storage landscape.

He believes zinc bromide can make commercial gains in the next 10 years, if three main factors are considered: cost, its long duration capabilities and safety.

Other factors include longevity of the system and its inherent stability that prevents degradation of the cell at the rate of other chemistries, such as lithium ion and lead acid where the manufacturer and end user both accept the batteries life cycle limitations.

Kreiner said: “This all adds up, along with cheaper materials, to the overall system costs, and the cost per kilowatt hour.”

Flow batteries are touted as a next generation battery because of their long-duration, grid-scale capabilities that allow for services including peak shifting and load capacity.

Rongke Power is building an 880MWh vanadium flow battery in Dalian, China, which once completed will be the largest energy storage system in the world.

Here, Kreiner tells ESJB why zinc bromine technology is better placed than VRFB to meet grid-scale ESS services in the race to take a portion of the lithium ion market.

What are the big differences between zinc bromide and vanadium batteries?  

PK:      There’s a number of factors and some are specific to us. The biggest difference is the battery couple elements – i.e. the elements used to store energy. With vanadium the big drawback is the metal is very expensive, and it’s not very abundant.

With zinc bromide, the couple elements are zinc and bromine, which are extremely abundant, around a thousand times more so, and significantly lower cost on a per kWh basis.

Why have flow batteries not been commercialized to the level of lead or lithium

Because of cost concerns I’m not sure vanadium will every really take off commercially. As people look to the next generation of battery technology, there’s not a clear path for it to compete with lithium ion. So for vanadium to take a significant market share, I think it will boil down to cost.

With conventional zinc bromide, the main difficulty is you have to plate zinc onto one electrode. Keeping that zinc smooth, uniform, and free of dendrites is a challenge.

In the case of conventional zinc bromide batteries that is particularly challenging because of the membrane, which can be permanently damaged by dendrites.

The reason I believe Primus will overcome the issues other flow batteries have faced is twofold: 1) the chemistry enables lower cost, which addresses the main hurdle for vanadium and 2) our unique technology enables the zinc plating. We have demonstrated that we can plate zinc five times thicker than conventional zinc bromine batteries, and we don’t use a membrane so the stack is more robust.

We use titanium electrodes on both sides whereas conventional versions use graphite electrodes, and that has a number of advantages: it is more robust, lasts longer and allows us to plate more zinc, which means more energy on each electrode. This in turn means lower cost on a per kilowatt hour basis.

What are the market opportunities for flow batteries?

The analyses I’ve seen, and more and more research indicates, that the vast majority of energy storage needs will be served by long duration systems, around four to six hour duration at full power. That’s what we have targeted with our product. Flow batteries are better suited for long-duration services rather than lithium ion’s short duration capabilities.

The big categories are renewables integration, peak shaving, and deferral of distribution system spend.

Renewables integration means using batteries to take the intermittent power generated by renewable sources like wind and solar and turn it into steady power delivered when it’s needed, on-demand. In this way, batteries are key to enabling 100% renewable energy.

Peak shaving refers to charging batteries off-peak and discharging them during peak hours when usage spikes. This lets electricity users save money and reduces the peak load on the grid.

Distribution deferral refers to allowing a utility to delay spending large amounts of money to increase distribution capacity such as building new power lines and substations by instead spending a smaller amount of money on batteries that can deliver power during peak hours. In other words, a utility’s infrastructure can be sized more optimally; without storage a grid system has to able to meet the maximum demand, even if this maximum demand occurs only occasionally, which means higher cost infrastructure.

What applications can flow batteries help system operators meet?

I think renewables integration in the long term will be the most important and largest application for long duration energy storage. We are getting to the point where power produced from renewable sources is practically free and the key barrier to future deployment is the fact it is intermittent, and that’s where a long duration battery is important.

In the short term, I see the market as more behind the meter applications where customers can avoid high demand charges during peak times during the day. Although in the long term that will be a smaller proportion of the market, it is an important stepping stone and an area we predict zinc bromide can deliver.

How does a flow battery work, and how does your technology differ?

In conventional zinc bromide, from a system perspective they have two tanks and two pumps and flow loops with two sets of pipes carrying the two different types of electrolytes into the stacks. The reason for two separate loops is the electrodes in each battery cell are separated by an ion exchange membrane (often referred to as a separator).

In a flow battery, this membrane has significant cost implications; the membrane itself is expensive and it creates the need for twice as many flow components. Additionally, the membrane is a critical component that can wear out can limit the life of the battery. And with conventional zinc bromide in particular, the membrane can be damaged by dendrites.

The unique thing with Primus is our battery doesn’t have a membrane. We do this through innovations in both our electrolyte and electrode. The result is we’ve eliminated an expensive component that can limit the life of the battery, and we’ve also simplified the manufacturing process. Our system only has one tank and one pump. It cuts the complexity of the flow loop in half.

What is your 10 year plan?

Our technology is where we want it in term of efficiency and longevity, so the key in the next 10 years is driving down costs, which will be set by the cost of the battery elements zinc and bromide. We have a greater opportunity for cost reduction than lithium ion because our core costs, the raw materials in the battery, are already significantly lower.

If Zinc bromide is to make commercial gains in the next ten years, there are three main factors to consider: cost, its long duration capabilities and safety. The longevity of the system – its inherent stability that prevents degradation of the cell at the rate of other chemistries, further strengthens the cost advantage by reducing the need for cell replacements and thereby reducing lifetime cost.

Some installations that use lithium ion have to factor in the degradation, down to around 80% — or even less, I’ve seen warranties that only guarantee 60-70%— after ten years, so the end user has been known to either oversize the battery initially, so after a decade it is still able to perform the required task, or factor in the cost of even more frequent upgrades to the system.

What would be your take home message about zinc bromine flow batteries?

By using titanium and no membrane, our system has a longer life than conventional zinc bromide and vanadium flow batteries. These factors also allow us to store more energy on the electrodes, which leads to our ability to offer fundamentally lower costs even than conventional zinc bromide. Looking ahead at the long term direction of energy storage, this cost advantage is a key factor if any battery product is to become competitive with lithium ion.