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Storage Steps Up

Could grid-integrated batteries change the way power producers operate fossil power plants?

Feb. 26, 2014: Duke Energy Renewables’ 153-MW Notrees (Texas) Wind Power Project includes a 36-MW advanced lead acid battery – the largest capacity battery facility in North America.

Funded by Duke and the U.S. DOE (50 percent) under the American Recovery and Reinvestment Act smart grid program, the $43 million battery project helps smooth the Notrees wind farm’s naturally variable output. By storing wind energy, the battery can respond quickly to regulate frequency and also provide ancillary services for grid management.

Duke says developing expertise in this advanced technology will help expand the use of renewable energy, better integrate it into the power grid, and make the company more efficient at serving customers. Could batteries and other storage technologies affect the way power producers evaluate and operate their generating assets – in particular fossil fired generating assets they currently rely on to supply ancillary services?

With a year’s worth of commercial operation now in the books at Notrees, Fortnightly’s Power Profit recently spoke with Jeff Gates, managing director in Duke Energy’s commercial transmission business, about the Notrees operating results and the future of battery storage.

FPP What's the status of the Notrees storage project?

Jeff Gates, Duke Energy:  We just completed a year of commercial operation and we’re preparing our first report for DOE. It will include operating data and data on the greenhouse gas reductions ERCOT achieved by using this emission-free resource instead of gas-fired generation. The report should be out in another month or so.

FPP You’re examining the emissions saved by the capacity you supplied ERCOT, versus a gas plant doing the same thing?

Gates: Yes, we’re compiling that information. But there are other benefits too. One of the key strengths of storage delivery is that it’s so much faster and more accurate. If the system frequency level moves to one side of 60 Hz or the other, ERCOT will send a signal to  increase or decrease output. A conventional power plant can take several minutes to ramp to the new output level, so the grid operator has plants that are chasing the signal. By the time they reach their new dispatch level, the grid operator may actually want them doing just the opposite, as the frequency may have crossed 60Hz again in the other direction. With storage we’re not chasing the signal, because the battery can respond with full output to whatever signal they give us within less than a second.

It’s like turning the shower on at home – you want it to be warm, but it’s not, so you turn the temperature up higher, then the really hot water kicks in and you turn it down a bit. You adjust it until you get the perfect temperature. If there’s a two-minute lag every time you try to adjust the temperature, it’s very hard to tune in the perfect temperature quickly. It’s always too hot or too cold. But if it were at whatever temperature it’s going to be within a second, it would be very easy to fine tune it to exactly what you want.