Greentech Media

Most traditional battery chemicals aren’t suitable for wind power, Bradford said. "You need a battery that can buffer really high capacity demands," she said, adding that lead-acid batteries, for example, would require a "humungous" battery bank to handle that need.

But sodium-sulfur seems promising because the technology has achieved efficiencies of more than 89 percent and pulse power -- the ability of a battery to deliver energy at full power without reducing its reliability or its lifespan -- of six times the current ratings, she said.
 
Still, price remains an issue, she said. In September, AEP said its project would cost about $4,500 per kilowatt. Xcel said it hadn’t worked out the pricing yet, but had received a $1 million grant from Minnesota’s Renewable Development Fund, subject to approval from the state’s public utilities commission.

"It has potential," Bradford said, referring to sulfur-sodium technology. "There certainly are some big names looking at it -- there are certainly some benefits -- and I think this could be an option. But I think it’s so soon, in terms of commercializing it, that it’s hard to tell if the prices will come down [enough]."

Another issue? So far, only one manufacturer produces sodium-sulfur batteries, she said.

"That kind of puts a freeze [on the market] unless they start licensing it out," she said. "That would be a long-term challenge."

Meanwhile, other competitors -- both startups and traditional battery players -- are chomping at the bit to try to take a bite of the potential utility energy-storage market.

"I know the traditional battery guys would love to get to that market, but they haven’t been able to do it yet," Bradford said.