Flow Batteries Struggle in 2019 as Lithium-Ion Marches On h


Save for a few rare announcements, the promising technology class has gone quiet.

October’s SoftBank-led investment in iron flow battery startup ESSrepresented an unusual event in 2019: a piece of good news for the flow battery sector. The $30 million cash injection was a rare sign that there may still be life in an energy storage technology class that had almost faded from view in recent months.

Leading players such as Sumitomo Electric and Dalian Rongke Power, the latter of which once boasted the world’s largest vanadium flow battery project, have gone silent. EnSync Energy Systems pivoted away from flow batteries last year and folded in March.

CellCube Energy Storage Systems has also run into problems this year. In October it advised shareholders that “each division is suffering from a lack of working capital” and added that management was “reviewing strategic alternatives focused on maximizing shareholder value.”

Go Big: This factory produces vanadium redox-flow batteries destined for the world’s largest battery site: a 200-megawatt, 800-megawatt-hour storage station in China’s Liaoning province.

Even those companies still touting contract wins in 2019 have hardly set the world on fire. RedT Energy installed Australia’s largest commercial energy storage system, a 1-megawatt-hour system at Monash University, but more recently announced a merger with Avalon following reported losses.

Meanwhile, UniEnergy Technology’s sole deal-related press release this year was to celebrate the commissioning of a 7.5-kilowatt, 30-kilowatt-hour flow battery in Brussels.

Despite this, a smattering of players, including Avalon, Lockheed Martin and U.S. Vanadium, remain bullish. And Dan Finn-Foley, head of energy storage at Wood Mackenzie Power & Renewables, cautions against writing the sector off just yet.

“We haven’t seen much activity from the flow battery space in terms of deployments or major announcements,” he acknowledged, “but there are key steps happening behind the scenes.”

Researchers advancing flow battery technology are either partnering with companies with large balance sheets or securing insurance to back up their claims of long system lifetimes and low degradation, he said.

“The next steps will be continued pilot programs and strategic targeting of favorable market niches, all critical stepping stones toward true commercialization,” Finn-Foley said.

Image: Vanadium Redox Flow Batteries 

Flow battery vendors could benefit from state-level 100 percent clean or renewable energy policies in the U.S., Finn-Foley noted, since it is remains unclear whether lithium-ion batteries alone can meet storage needs beyond durations of approximately eight hours.

Flow batteries are seen as ideal for large-scale, long-duration storage because they can store large amounts of energy using scalable tanks of relatively cheap electrolyte. The problem is that nobody seems to need this long-duration capacity just yet.

Finn-Foley said the biggest unknowns for the flow battery sector “are the timing of when these long-duration needs will emerge and how low vendors will be able to drive costs by then with few other opportunities to scale.”

This is emerging as a significant issue in 2019. While flow battery technology is waiting for prime time, its main competitor, lithium-ion, is already racing ahead on scale and cost-competitiveness thanks to the growth of the electric vehicle industry.

In March, QY Research Group predicted the global redox flow battery market would be worth $370 million by 2025, based on a roughly 14 percent compound annual growth rate (CAGR) from 2018.

For comparison, a May study by Prescient & Strategic Intelligence estimated the lithium-ion market would be worth close to $107 billionby 2024, with a CAGR of almost 22 percent.

Even ignoring the fact that the lithium-ion industry is on a quest to use lower-cost materials, it is hard to see how flow batteries will be able to compete on price against such a thoroughly commoditized rival.

The state of play was perhaps best summed up by Rebecca Kujawa, chief financial officer and executive vice president of finance at NextEra Energy, during an earnings call in October.

Asked by Pavel Molchanov, an analyst at Raymond James & Associates, whether NextEra had found any storage technologies other than lithium-ion that are worth commercializing, she said: “We always remain technology-agnostic.”

But she added: “What we continue to see, and what we are currently signing contracts for with our customers, is predominantly lithium-ion. Those producing lithium-ion batteries are investing in manufacturing scale, which is producing significant cost improvements.”

Kujawa concluded: “In the middle part of the next decade, you’re talking about a $5 to $7 per megawatt-hour added to get to a nearly firm wind or solar resource, and that’s a pretty attractive price.

Image: 100% Renewable Energy

To beat that, you’d have to see a pretty big step change in where some of these other technologies are.”

Long-lasting flow battery could run for more than a decade with minimum upkeep – Harvard Paulson School of Engineering 


Battery stores energy in nontoxic, noncorrosive aqueous solutions

Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a new flow battery that stores energy in organic molecules dissolved in neutral pH water.

This new chemistry allows for a non-toxic, non-corrosive battery with an exceptionally long lifetime and offers the potential to significantly decrease the costs of production.

The research, published in ACS Energy Letters, was led by Michael Aziz, the Gene and Tracy Sykes Professor of Materials and Energy Technologies and Roy Gordon, the Thomas Dudley Cabot Professor of Chemistry and Professor of Materials Science.

Flow batteries store energy in liquid solutions in external tanks — the bigger the tanks, the more energy they store.


Flow batteries are a promising storage solution for renewable, intermittent energy like wind and solar but today’s flow batteries often suffer degraded energy storage capacity after many charge-discharge cycles, requiring periodic maintenance of the electrolyte to restore the capacity.




By modifying the structures of molecules used in the positive and negative electrolyte solutions, and making them water soluble, the Harvard team was able to engineer a battery that loses only one percent of its capacity per 1000 cycles.


“Lithium ion batteries don’t even survive 1000 complete charge/discharge cycles,” said Aziz.

“Because we were able to dissolve the electrolytes in neutral water, this is a long-lasting battery that you could put in your basement,” said Gordon.

 

 

“If it spilled on the floor, it wouldn’t eat the concrete and since the medium is noncorrosive, you can use cheaper materials to build the components of the batteries, like the tanks and pumps.”

This reduction of cost is important. The Department of Energy (DOE) has set a goal of building a battery that can store energy for less than $100 per kilowatt-hour, which would make stored wind and solar energy competitive with energy produced from traditional power plants.


“If you can get anywhere near this cost target then you change the world,” said Aziz. “It becomes cost effective to put batteries in so many places. This research puts us one step closer to reaching that target.”

“If you can get anywhere near this cost target then you change the world,” said Aziz. “It becomes cost effective to put batteries in so many places. This research puts us one step closer to reaching that target.”

“This work on aqueous soluble organic electrolytes is of high significance in pointing the way towards future batteries with vastly improved cycle life and considerably lower cost,” said Imre Gyuk, Director of Energy Storage Research at the Office of Electricity of the DOE.

“I expect that efficient, long duration flow batteries will become standard as part of the infrastructure of the electric grid.”

The key to designing the battery was to first figure out why previous molecules were degrading so quickly in neutral solutions, said Eugene Beh, a postdoctoral fellow and first author of the paper.

By first identifying how the molecule viologen in the negative electrolyte was decomposing, Beh was able to modify its molecular structure to make it more resilient.

Next, the team turned to ferrocene, a molecule well known for its electrochemical properties, for the positive electrolyte.

“Ferrocene is great for storing charge but is completely insoluble in water,” said Beh. “It has been used in other batteries with organic solvents, which are flammable and expensive.”

But by functionalizing ferrocene molecules the same way as the viologen, the team was able to turn an insoluble molecule into a highly soluble one that could be cycled stably.

“Aqueous soluble ferrocenes represent a whole new class of molecules for flow batteries,” said Aziz.

The neutral pH should be especially helpful in lowering the cost of the ion-selective membrane that separates the two sides of the battery.

Most flow batteries today use expensive polymers that can withstand the aggressive chemistry inside the battery. They can account for up to one-third of the total cost of the device. 


With essentially salt water on both sides of the membrane, expensive polymers can be replaced by cheap hydrocarbons. 

This research was coauthored by Diana De Porcellinis, Rebecca Gracia, and Kay Xia. It was supported by the Office of Electricity Delivery and Energy Reliability of the DOE and by the DOE’s Advanced Research Projects Agency-Energy.

With assistance from Harvard’s Office of Technology Development (OTD), the researchers are working with several companies to scale up the technology for industrial applications and to optimize the interactions between the membrane and the electrolyte.

Harvard OTD has filed a portfolio of pending patents on innovations in flow battery technology.