Over the past few years, flow battery startups such as Prudent Energy, Primus Power, EnerVault, Imergy (formerly Deeya Energy), and others have been vying for media attention for their attempts to bring this potentially disruptive technology for long-term, grid-scale energy storage to the commercial market.

Meanwhile, there’s another flow battery maker with dozens of commercial-scale projects under its belt that has hardly spoken about its technology. That’s Germany’s Gildemeister, a century-old industrial machine tools maker with a majority stake in Cellstrom, the Austrian-based maker of the CellCube vanadium redox flow battery system.

Gildemeister has reportedly sold more than 50 of its CellCube devices in Europe and Asia, including a project with German utility E.ON. It’s also working with partner Younicos to create “battery parks” meant to serve broad grid-balancing functions in Europe’s increasingly renewable-energy-disrupted energy markets. But the company hasn’t made much of a splash here in the United States. 

That hasn’t been for want of trying from partner American Vanadium, however. The Canadian mining company has been Gildemeister’s North American distribution partner since May 2013, and CEO Bill Radvak has been promoting the technology heavily at trade shows and conferences since then.

Last week, the Vancouver, British Columbia-based company announced a potential milestone in those efforts, with the delivery of the first Cellcube units for testing by the Department of Energy’s National Renewable Energy Laboratory (NREL) in Golden, Colorado. That testing could be complete by this summer, at which point at least one U.S. utility, as well as various integration partners, are interested in deploying it stateside, Radvak told me in a phone interview last week.

Radvak declined to say which U.S. utility planned to deploy Gildemeister’s Cellcube units. But a November blog post from Crystal Equity Research noted that American Vanadium has proposed a trial with New York State Energy Research and Development Agency (NYSERDA) to demonstrate a Cellcube unit in Manhattan, in partnership with Consolidated Edison and the NY-BEST energy storage industry group.

That jibes with a recent contributed article Radvak wrote for Greentech Media, noting New York state’s newly created grid-scale storage incentives as a development that will open that market to new opportunities. It’s also aligned with ConEd’s work testing new battery technologies as part of its goal of reducing grid congestion and improving reliability in New York City.

As for the NREL tests, “This is a pretty all-encompassing grid trial,” Radvak said, including grid-connected and off-grid applications involving long-term storage and balancing of renewables like solar and wind power. “We don't believe that they’ve been able to test a long-duration, larger battery -- likely because there aren’t any commercially available, long-duration, multi-hour batteries out there.”

Flow Batteries’ Role in Long-Term Grid Energy Storage

He may be right. While lithium-ion batteries developed for consumer electronics and electric vehicles are increasingly finding their way into grid applications, they’re better suited for storing large amounts of energy over shorter durations, rarely for more than an hour or two.

Flow batteries, by contrast, pump liquid electrolytes through stacks of electrochemical cells, instead of containing them in closed systems, allowing for replacement of depleted materials and reduction of the degradation of the anode and cathode materials involved. That could help them store megawatts of grid energy over multiple hours of time at costs that could compete with alternatives like natural-gas-fired power plants.

Gildemeister, which since 2009 has been part of a strategic partnership with Japan’s DMG Mori Seiki and took that company’s name as its own in September, has been very shy about revealing details of its Cellcube deployments. It declined interview requests from Greentech Media in mid-2013.

But piecing together various announcements and company information indicates that the Cellcube devices come in modular units of 200 kilowatts, with a rating of 1.6 megawatt-hours per unit, which indicates they’re capable of delivering power for up to eight hours.

Other grid-scale batteries, such as sodium-sulfur technologies, can store energy for long periods, but operate at high temperatures and require a good deal of hands-on maintenance, whereas flow batteries have been deployed to back up cellphone towers for years now with little complaint. Startup Xtreme Power’s advanced lead-acid batteries have some long-term storage capabilities, but with its recently announced bankruptcy, it’s unclear whether that technology has a future.

While emerging technologies like Eos’ zinc-based batteries, Aquion’s sodium-aqueous batteries or Ambri’s liquid-metal batteries could achieve breakout energy storage durations at competitive cost, they’re still years away from commercial production.

The drawbacks for flow batteries include their reliance on pumps that may be subject to mechanical trouble and expensive maintenance, as well as their relatively low “round-trip” energy efficiency ( a measure of how much energy put into the battery can be retrieved from it). Flow batteries tend to hover at 60 percent efficiency and strive for 70 percent, whereas lithium-ion batteries can theoretically get back more than 90 percent of the energy put into them.

But if the difference between the value of the energy being stored and the energy being put back into the grid is broad enough, those efficiencies may still pay off. Consider wind farm operators that may want to store energy when grid prices go negative and bid it back to firm their output, or solar systems that could store power to meet late afternoon grid ramping needs that are emerging in solar-rich grids.

Business cases like these are already starting to pencil out on isolated grids where storage can replace expensive, polluting diesel fuel-fired generation. Now Gildemeister and American Vanadium are hoping to see broader applications, particularly in markets that are mandating energy storage, such as California, or are beginning to offer incentives for grid-scale projects such as New York state.

Breaking Ground on U.S. Production of Vanadium for Grid Storage

Different flow batteries use different chemicals, including zinc-bromine and iron-chrome combinations, as well as vanadium -- a much rarer metal, but one unique in its ability to undergo multiple phases of electrical charge. Vanadium is used almost exclusively for strengthening steel today, and China, Russia and South Africa are the countries where it’s mined at commercial scale, Radvak said.

American Vanadium was founded in 2006 with the goal of opening up the first large-scale vanadium mining and refining project in the United States. That’s its Gibellini project, a well-known but poor-grade deposit of vanadium in Nevada that has been worked on and off since World War Two.

The vanadium deposits at the Gibellini site will be extracted via a sulfuric acid leaching process, at a cost of about $5 per pound, compared to the $6 to $12 per pound the metal fetches on global markets, he said. Importantly, the vanadium-acid mixture that results could be almost directly put to use as a battery electrolyte, he claimed -- and Gildemeister has agreed to buy all the electrolyte it needs for its North American Cellcube deployments through American Vanadium.

Going from concept to full-scale mining operation will take more time and money, of course. The scale-up of the Gibellini project could cost $100 million or more, and isn’t expected to get underway until 2015 or so, Radvak said. In the nearer term, American Vanadium plans to set up a vanadium electrolyte production facility to supply Cellcube deployments, and potentially other flow battery makers, as long as they’re not competitive with Gildemeister, he said.

American Vanadium, which is traded on the TSX Venture Exchange under the symbol AVC, raised $1.5 million Canadian ($1.6 million) in late 2012. Late last year it announced the closing of two tranches of private placements of shares and warrants, valued at about $4.065 million Canadian ($3.66 million) and $1.765 million Canadian ($1.59 million), for a total of about $5.25 million, both centered on its role as an energy storage materials supplier. 

The company’s stock has been trading in the sub-40 cents per share range in recent months, and has seen a steady decline in price from its early 2011 high of $1.92 per share. A long path lies before it in getting Gildemeister’s Cellcube tested by NREL, deploying it in North America, and building up a resulting vanadium electrolyte business. 

Tags: ambri, american vanadium, aquion, batteries, cellcube, energy storage, enervault, eos, flow battery, gildemeister, grid storage, imergy, primus power, prudent energy, sodium-sulfur