Call it the million-megawatt question.
Is there a practical, effective way to store energy on a large enough scale to ease bottlenecks on the regional electric power grid? Researchers have pursued multiple paths looking for an answer.
The latest possibility is sitting on a trailer at Vancouver’s Ross Complex substation.The Bonneville Power Administration facility this year began the first extended test drive of a transportable battery storage system. Researchers with BPA, Pacific Northwest National Laboratory and other partners are exploring the capabilities of a new technology they hope could offer a bank to hold excess energy when it’s not needed, and withdraw it when it is.
If successful, the system could be expanded and dispatched to alter the landscape of a strained Northwest transmission grid. Officials say the concept could defer costly expansion of the existing system, saving local ratepayers’ money in the long run. And it may help resolve an overgeneration problem that has put BPA and its wind energy producers at odds.
Jeff Hildreth, a BPA electrical engineer, doesn’t understate the potential.
“Energy storage is sort of the holy grail,” Hildreth said. “Ultimately there’s no good way to do that right now.”
Testing on the battery storage system will stay relatively small-scale for now. Researchers are working with a single unit, plugged into a medium power lab at Ross Complex. It’s not connected to the rest of the grid.
“Any time you have a new project on the system, the last thing you want is to have it disrupt service to customers,” Hildreth said. “We’re pretty insulated from that here.”
The battery system, developed by Tualatin, Ore.-based Powin Energy, offers a more efficient and economical power converter system than any available in the industry, according to BPA. It’s about 85 percent efficient, said BPA spokesman Joel Scruggs — that is, you can recover close to 85 percent of the energy you put into it for re-use.
A recent demonstration gave researchers and visitors a first-hand look. As Powin executives dialed the battery unit up and down outside, a small group watched the glowing red numbers of a “battery feeder” reading dance back and forth in the lab.
The numbers showed a two-way connection. The reading climbed as high as 60 kilowatts — meaning the battery was absorbing energy off the system, or charging. At negative 60 kilowatts, the unit began to pump energy back into the facility.
The unit is a 120-kilowatt battery. That’s the “engine size,” said Virgil Beaston, Powin’s chief technology officer. Its capacity — the “size of the gas tank,” Beaston said — is about 500 kilowatt-hours. That’s enough to power about 100 homes for four hours.
Of course, a system as large as the Northwest power grid is measured in megawatts, not kilowatts. But integrating battery storage into that landscape wouldn’t mean building a supersized version of the unit at Ross Complex. It would mean producing the same unit many times over, dispatching batteries where they’re needed to balance load inconsistencies, when power supply and demand aren’t in sync.
“We could have hundreds or thousands of these deployed,” Beaston said.
The same concept could be applied on a smaller scale, Beaston said. Such battery units could also provide flexibility and a backup power source for local utilities during an outage, he said.
Researchers are a long way from realizing those possibilities. Study of the Powin system — a two-year effort — is just getting started. The battery unit will continue testing at Ross Complex through the end of March. Then it’s off to a wind farm near Kennewick. The unit will connect to the grid at a city of Richland substation in early 2014, before additional testing at a Pacific Northwest National Laboratory facility.
The entire project will cost an estimated $624,400. BPA will cover $240,000 of that, according to the agency.
‘Difficult to balance’
The energy storage concept has been applied to the natural gas facilities that are common across the country. But the electrical grid is a different story, and power managers haven’t found a practical way to capture and retrieve energy on a large scale. That’s something most people don’t realize, Scruggs said.
Besides the battery system, other studies are ongoing. BPA and the Pacific Northwest National Laboratory are also collaborating on a study that’s exploring the possibility of pumping compressed air or water underground as a means of energy storage. That research has yielded some promising results, said BPA project manager Steve Knudsen. More details are expected in a report due out later this year.
Excess energy has been a challenge for BPA at times recently. That’s particularly true in the spring, when high winds and high flows on the Columbia River can give power managers more energy than they know what to do with.
Largely fueling that dynamic is the ever-growing forest of wind turbines now pumping new energy into the Northwest grid. Wind farms in Washington and Oregon alone add up to almost 6,000 megawatts of capacity, according to the American Wind Energy Association, an industry lobbying group. Most of those turbines dot the landscape in and around the Columbia River Gorge.
“It’s really very significant in terms of integrating renewable energy … that comes when the sun shines or the wind blows,” Knudsen said. “It’s becoming increasingly difficult to balance.”
Managers can dial down production on BPA’s hydroelectric dams, but only so much. Spilling too much water violates water quality standards and can harm fish, according to BPA.
The issue has created friction between BPA and the wind energy producers on its grid. The agency has forced wind farms to shut down production at times, over the objections of wind producers, when the system can’t handle the excess power load. BPA now provides some compensation for lost revenue when that happens.
The dispute led BPA to develop an “oversupply management protocol.” But so far, the plan hasn’t passed muster with the Federal Energy Regulatory Commission.
A battery system could offer one solution to that power squeeze, said John Steigers, generation project manager with Energy Northwest, a partner in the research. Having the battery unit at Energy Northwest’s Nine Canyon Wind Project by this spring will give researchers a chance to test some real-world scenarios during the peak generation season, he said.
And as one of the wind farms subject to the shut-down orders of recent years, Nine Canyon knows the impacts of over-generation first-hand.
“I would say it’s one of the biggest issues facing the industry in the Northwest right now,” Steigers said. “And it’s very complex.”
For now, power managers continue to juggle supply and demand through a portfolio that includes wildly variable power sources. Energy storage, Knudsen said, may go a long way in addressing that challenge.
“Storage is becoming increasingly valuable to the system to essentially allow continued expansion of renewable energy — without creating reliability issues or adverse economic impact,” Knudsen said.