It’s the fatal flaw of wind power: once the wind stops blowing, the power stops flowing — or does it?
Researchers from the University of Minnesota are using the nation’s first wind-to-battery system as a model for developing techniques to harness wind energy so it can be stored and used later. Currently, most wind farms don’t have the capability to store excess energy from windy days to be used on calm days.
Since February, seven wind turbines in Luverne, Minn. have been connected to an 80-ton battery to test its ability to store the power generated and release it at varying time intervals.
The operation is hooked up to computer software that allows chemical engineering professor William Smyrl and electrical engineering professor Ned Mohan to monitor it online. So far, things are running smoothly, Smyrl said.
Xcel Energy purchased the battery, the size of two semitrailers, from a Japanese supplier in early 2008. The company has poured at least $1 million into the project.
Frank Novachek, Xcel’s director of corporate planning , said storing wind energy will act as a shock absorber and help their system run more efficiently.
“It would smooth out the ups and downs that wind has on our system,” he said.
There are often times when Xcel doesn’t use all of the energy generated by a wind farm in a given day, and without a way to store it, that energy is lost, Novachek said.
For Mohan, the big question surrounds the amount of storage capacity a battery must have in order to sufficiently supply the power grid with wind energy.
Although the feasibility and cost-effectiveness of storage is still unclear, it’s important to use wind power as much and as soon as possible, Mohan said. Smyrl said wind power is attractive because it’s completely clean; nothing is burned or emitted. He also pointed out its easy maintenance.
“Once you put up wind turbines, all you have to do is watch them work,” he said.
As of now, it’s a small-scale project, running on a one-megawatt storage system, significantly less than most wind farms, which operate in the realm of 200 to 400 mega-watts.
Other large-scale renewable energy techniques, like pumped hydropower and compressed air storage, operate at levels of 300 mega-watts or more, Smyrl said.
It would take a lot of batteries for the wind-to-battery technique to reach that level. In Luverne, for example, it would mean 300 more batteries — or a warehouse-full rather than a shed-full, Smyrl said, adding that when it would come down to running them all simultaneously, “that’s a bigger headache.”
The largest barrier to the project is the high cost of the batteries, Novachek said, although he’s confident the price will go down in the future.
The project comes after the state passed a law in February requiring utility companies to generate 25 percent of their energy from renewable sources by 2025. For Xcel Energy, which provides half of the state’s energy, the standards are stricter, requiring that 30 percent of their output come from renewables by 2020, with at least 25 percent of the renewable energy being wind.
Although he’s confident Xcel will be able to reach that goal without the use of wind storage, Novachek said he hopes the project will increase their capacity to use wind power.
“We are trying to do whatever we can to take on as much renewable energy as possible,” he said. “We believe that storage will help us to do that.”