ADVERTISEMENT

Molten Metal Batteries Return for Renewable Energy Storage

New ideas for making sodium sulfur batteries could make them the answer for taming the variability of wind and solar power
The Streator Cayuga Ridge South Wind Farm



Courtesy Energy.gov

EaglePicher Technologies, a manufacturer of specialized batteries for military and space programs, is partnered with the federal government to develop a powerful battery storage technology to help utilities smooth out the ups and downs of renewable power.

It's a familiar path for the Joplin, Mo., company.

EaglePicher began developing a battery for space applications in the mid-1980s that used sodium and sulfur components. Its model performed successfully on the Columbia space shuttle in 1997.

But by then, the focus for military and space batteries had shifted to lithium-ion models in the United States and the impetus for a sodium sulfur battery vanished in this country. EaglePicher mothballed its work.

Now EaglePicher is back in the game, working on a sodium sulfur battery with the Pacific Northwest National Laboratory (PNNL), backed by a $7.2 million grant from the Energy Department's Advanced Research Projects Agency-Energy (ARPA-E). It was one of 37 such awards made in 2009 to foster clean energy breakthroughs. EaglePicher is funding the $1.8 million balance of the three-year project.

With Energy Department research and development budgets facing an uncertain future in Congress, the future for such clean energy partnerships is also uncertain. This week, ARPA-E will show off its grantees at the 2011 Innovation Summit in Washington, bringing together scientists, venture capital funders and elected officials in a bid for political support for President Obama's goal of producing 80 percent of the U.S. electricity supply from clean energy sources by 2035.

PNNL estimates that more than 200,000 megawatt-hours of power from energy storage would be needed in 2030 if the United States were to get 20 percent of its electricity from renewable sources then. The concept is to store electricity made from renewable energy when it is in surplus -- such as wind energy at night -- and use it during during peak demand periods during the day.

The characteristics of sodium sulfur batteries are well-suited for that. While the technology was pioneered in this country, but then abandoned, Japan saw the promise and picked it up. Its Ministry of International Trade and Industry chose it as a targeted opportunity.

Japan takes the idea and runs with it
Tokyo Electric Power Co. and NGK Insulators pushed sodium sulfur development in the 1990s, and today, NGK is the primary commercial manufacturer. U.S. utilities seeking large storage batteries for renewable energy can face a wait of a year or more.

It amounts to the second big battery technology fumble the United States has been involved with. The technology that underpins the ubiquitous lithium-ion batteries in consumer electronics products was invented by American physicist John Goodenough in the late 1970s, helped by a $20,000 grant from the U.S. Air Force. Ignored by U.S. manufacturers, it was commercialized by Sony and other Japanese companies in the 1990s.

PNNL scientist and project coordinator Gordon Graff says the laboratory's partnership with EaglePicher seeks to leapfrog NGK's design to perfect a more compact architecture that could significantly boost the battery's efficiency and performance while also greatly simplifying the manufacturing process.

"This is a radical change in design," said Graff, who holds 22 patents. "This is one of the ways we can make this step jump."

In the PNNL facility in Richland, Wash., Graff hefts one of the NGK batteries as he explains the opportunities that PNNL and EaglePicher team hope to exploit.

The NGK battery is a cylinder with sodium in the center, separated from molten sulfur by a ceramic membrane that allows the passage of sodium ions to create the battery's current. The tubular design of the NGK membrane and casings simplifies maintaining a secure seal on the volatile chemicals within the battery, whose internal temperature reaches 350 degrees Celsius.

If the battery can be made instead with a flat, planar membrane encased in a box-like structure, the battery could deliver more power, at lower temperatures, and would be sturdier and be far simpler to mass produce, says David Lucero, who directs EaglePicher's advanced battery project. "We think the planar design could increase performance by 30 percent, getting more energy in a smaller package," said Lucero.

Reinventing a reinvention
"You should be able to get roughly a 25 to 30 percent reduction in costs because it's so much easier to manufacture sheets of materials than closed-end tubes," Graff said. The membrane that separates sodium and sulfur components can be made much thinner in the flattened design, he added.

Like other ARPA-E funded projects, this one is no sure thing.

"There are many problems," Graff said. "One of the biggest ones is seals. In this geometry, all you have to seal is the top lip," he said, holding up the NGK model. A fail-safe seal is harder to achieve in the flattened design, he said. "Why would you even attack that?" Graff asked. Because the lab has been working on planar designs for 15 years, he said, answering his own question.

Most of the first year's work was basic research at PNNL. "As we begin year two, we are transferring the work here, to scale up to the final demonstration," Lucero said. The team is pleased with the progress made so far, but there are still risks.

"We're doing very, very well," Graff said. The goal for PNNL and EaglePicher is to deliver a 5-kilowatt battery producing 10 kilowatt-hours of energy by the end of 2012.

ARPA-E has set milestones for each stage of the project, Lucero said. "The project is reviewed on a quarterly basis to make certain the development is advancing satisfactorily. These are very aggressive go-no go types of metrics that we have to achieve.

"ARPA-E is not doing science for science's sake," Lucero added. "They wanted a science-industry partnership product technology that has a better chance of being utilized. There is a cost share to make sure that the industry partner has skin in the game."

The ARPA-E funding should allow for the completion of the three-year demonstration project, PNNL says. Then, if the technology challenges are met, the future of this sodium sulfur battery is likely to be determined by intersecting policy and market forces, including the size and growth of the renewable power industry and the availability of hundreds of millions of dollars in capital to eventually to move to commercial production.

It's happened before. "In the mid-90s, NGK made significant investments developing the technology so they could commercialize it," Lucero said. "They were pretty visionary."

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500

Share this Article:

Comments

You must sign in or register as a ScientificAmerican.com member to submit a comment.
Scientific American Special Universe

Get the latest Special Collector's edition

Secrets of the Universe: Past, Present, Future

Order Now >

X

Email this Article

X