For all of vanadium’s promise, it still faces skeptics—including, surprisingly, some in the wind-power business who think the energy storage problem is not such a big deal. One big sticking point is price. Vanadium batteries currently cost about $500 per kilowatt-hour. So to run a city of 250,000 for 24 hours off a vanadium battery, the price tag would come to $2.4 billion. “Storage is not needed for wind, and it is unlikely to be cost effective in the next decade,” argues Rob Gramlich, policy director of the American Wind Energy Association. Gramlich points out that a recent U.S. Department of Energy report, “20% Wind Energy by 2030,” hardly mentions storage. He notes, too, that Denmark, the world’s most enthusiastic user of wind power, gets by without storage.
How do the Danes do it? The grid in western Denmark is strongly interconnected with those of Norway, Sweden, and Germany, which act as giant energy sponges for their neighbor. They sop up cheap surplus power from Denmark when the wind is blowing and return expensive hydroelectric power during peak periods. The result is that, although 17 percent of the electricity the Danes generate comes from wind, they use only 7 or 8 percent, according to Hugh Sharman of Incoteco, a Denmark-based energy consultancy and development company whose clients include VRB. The rest is exported.
That situation will not be sustainable if the countries add more renewable power—and the Danes propose building another 4.5 gigawatts’ worth of offshore wind farms. That leaves two ways of meeting electricity demand when the wind drops. Either build lots of small, fast-acting, fossil-fueled backup turbines, or go for storage. As the price of natural gas soars, battery storage is rapidly becoming a more economically appealing option. Researchers at the Riso National Laboratory for Sustainable Energy in Roskilde, Denmark, are currently evaluating a 15-kilowatt VRB battery.
Cost is not the only obstacle that the vanadium battery has to overcome. Reliability may also be an issue, following the shutdown last year of a vanadium battery showcase, a 200-kilowatt backup system that was installed in 2003 at a wind farm on King Island, off the northern coast of Tasmania. A problem with the plant’s battery (which was not supplied by VRB) caused the electrolyte to overheat, damaging the stack. Still, other demonstration vanadium batteries, such as a 250-kilowatt installation at Castle Rock, Utah, have been operating reliably for years.
One vote of confidence comes from China. A group led by Huamin Zhang at the Dalian Institute of Chemical Physics in northern China has finished testing 2-, 5-, and 10-kilowatt vanadium battery modules and is currently evaluating a 100-kilowatt system. Vanadium “will have a potential market in China with the increasing development of renewable energy supported by the Chinese government,” Zhang wrote in an e-mail message. “Furthermore, large-scale energy storage systems are strongly needed in China [as backup during] frequent natural disasters” such as the recent Sichuan earthquake.
The greatest challenge to the vanadium battery may come from other advanced battery technologies, most seriously from sodium-sulfur batteries made by the Japanese ceramic specialist NGK Insulators. Though less scalable, sodium-sulfur has attracted investors because it is a more mature technology. Installations include the town of Rokkasho in northern Japan, where 34 megawatts of sodium-sulfur storage backs up 51 megawatts of wind turbines.
In the end, the vanadium battery has some uniquely appealing traits that may make it the best partner for renewable energy—not just for giant wind farms, but also for small-scale turbines and solar cells that bring renewable power directly into consumers’ homes. Currently, sodium-sulfur technology doesn’t work well at sizes below 1 megawatt. For smaller applications, such as regulating the flow of electricity from a house’s solar panels, vanadium-based systems look more cost-effective. They can be fit to more modest demands by using smaller tanks.
These smaller applications are where Skyllas-Kazacos is currently focusing her efforts. Three years ago she, along with her husband Michael and sons Nick and George, founded V-Fuel to develop and commercialize a second-generation vanadium battery. The impetus to found V-Fuel came when the University of New South Wales sold the rights to first-generation vanadium battery technology to VRB Power Systems. Two years later, with nothing left to develop, her battery lab—which at its height had 18 members—closed. Yet people kept contacting Skyllas-Kazacos about vanadium batteries, and she kept thinking up ideas for a better version. In 2005, at age 54, her husband wanted to retire. She told him, “No, you can’t—we’re starting again!”
“I could see so many opportunities,” Skyllas-Kazacos says, “but a lot of this interest wasn’t translating into real sales because the cost was just too expensive.” The key to cutting cost, she notes, is finding a replacement for the flow battery’s most expensive part, the membrane. Following a worldwide search for a suitable material, V-Fuel designed a polymer membrane that Skyllas-Kazacos claims is durable and less than half the price of conventional materials. A second challenge is making a smaller battery, one that does not need a warehouse to store electrolyte tanks. To do this, Skyllas-Kazacos has found an electrolyte that allows more vanadium to dissolve, thus doubling the energy storage density.
Atop a bench in V-Fuel’s cramped workshop in Sydney sits a prototype 5-kilowatt battery stack. The size of a filing-cabinet drawer, the stack is designed to be rack-mounted above a square block consisting of two electrolyte tanks. The resultant package would be compact enough to fit in a household closet. Configured as part of a home-based generation system, it could absorb power from rooftop solar panels and discharge electricity during peak periods. Skyllas-Kazacos estimates that such a consumer-use vanadium battery might eventually sell for around $5,000. At that price it could pay for itself in a few years.
So the vanadium battery may play a big role both invisibly at the electric utility and very visibly in the home, smoothing out Mother Nature’s rough edges so that renewable power works just as well as coal or natural gas. Stabilizing a future national grid that draws the majority of its power from renewable sources may seem like a tall order for a technology that delivers megawatts, not gigawatts, of power as it is used today, but some industry insiders are confident batteries can rise to the challenge. “At this point, [a 1.2-megawatt battery] is fairly large-scale, but we are at the front end of this curve,” Jim Kelly of Southern California Edison says. “Five years from now that will seem so trivial. It’s like comparing the first personal computer you had with the ones we have today. You look back and laugh. I think we’ll see that same thing happen with the battery industry. We are taking baby steps, in part because the industry is not mature, the technology winners have not been determined, and the costs are still high. But these are all the things you expect as a revolution happens.”
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Correction, the article was originally attributed to Robert rather than Bob Johnstone
*Correction, the article originally stated kilowatt-hours rather than watt-hours.