By JIM ROSS
The State Journal
CHARLESTON, W.Va. — An electric substation under construction in eastern Cabell County means a battery installation will find its third purpose in life.
Instead of preventing power fluctuations in a limited area or providing backup power when a transmission line goes down, the 2-megawatt battery at Balls Gap will keep the regional electricity grid in balance through a process known as frequency regulation.
The Battery already uses half its capacity in that role. When the new Balls Gap substation is finished and goes on line in December, the entire capacity will be used to keep the grid in balance during sudden jumps or drops in deman d.
In 2006, Appalachian Power needed a new substation in the Patrick Street area of Charleston. The transformer that served that area was exceeding its peak operating load, although it was not overloaded. So in an arrangement with the U.S. Department of Energy, Appalachian Power installed a 1-megawatt battery there at what it calls Chemical Station. The battery was charged at night from the power grid. It discharged when daytime loads began stressing the transformer. That continued until ApCo built the Patrick Street station, Wright said.
The battery used NaS, or liquid sodium and sulfur, technology. NaS batteries are known for their high-energy density, high-efficiency discharge and long life cycle.
The cells of the battery were built by NGK in Japan, Wright said.
NaS batteries operate at 300 to 350 degrees Celsius, or about 570 to 660 degrees Fahrenheit. The Chemical Station battery had heaters to keep the battery operating at its optimal temperature, Wright said.
“What happened at Chemical Station was that during one of the maintenance cycles, they discharged the cells and they allowed the temperature to drop faster than what it should, which caused damage to various cells,” he said. “Pretty soon the battery at Chemical Station got to the point where it wasn’t usable any longer. We decided to just retire that unit.”
So ApCo began looking for other opportunities to use a NaS battery, and one came up in the Milton area of Cabell County. Balls Gap is a rural area south of Milton. The Milton transformer was becoming heavily loaded, and ApCo figured it needed a new transformer in the Balls Gap area.
ApCo wanted to defer having to build another substation, so it repeated what it did in Kanawha County by placing a NaS battery at Balls Gap in 2009, although this time the battery had a 2-megawatt capacity instead of 1 megawatt, Wright said.
ApCo monitored the Milton area, and if the transformer was being used too heavily, the battery would kick on for backup, taking stress off the transformer, Wright said.
The battery had the added benefit of improving reliability for customers at the end of the Balls Gap line by using a technique called islanding, Wright said. If part of the system in that area went down, the Balls Gap line could be isolated and provide power to about 700 customers while repairs were made to the distribution system, he said.
In 2014, ApCo installed a second transformer at the Milton substation to address the overload in that area. Last year, the company began looking for options for the Balls Gap battery, such as moving it, Wright said.
The idea came up to use it for frequency stability on the PJM system. That’s the multistate regional grid that includes West Virginia. At times, the system needs extra power for a short time as demand fluctuates. Some sources can be added quickly. Some cannot. A battery is a fast-response system, Wright said.
“What we have at Balls Gap is a 2-megawatt battery, but it’s really two 1-megawatt batteries at the site,” he said. “We could still provide the islanding service, and we could also put one megawatt into the market to make it available to PJM.
Wright said he has not seen a report of how often the battery has been used or how it has performed.
“We’ll learn more as we go throughout the year. Probably in 2018 we’ll have a better understanding,” he said.
Battery power is something ApCo parent American Electric Power is investing in systemwide. AEP has batteries in other states, but they are smaller than the one at Balls Gap. ApCo spokeswoman Jeri Matheny said AEP plans to have 20 megawatts of battery storage by 2025.
Wright said batteries may be an answer to reliability issues in some parts of the ApCo service territory. For example, the Clendenin-Walton circuit is 300 miles of line that butts up against FirstEnergy territory. Eventually, a battery similar to Balls Gap could help with distribution system problems there, he said.
Further ahead, AEP is looking at using lithium ion batteries instead of NaS batteries in future deployments, Wright said. Among other things, there are more manufacturers of li-ion batteries than NaS batteries, so the company would not be as dependent on one supplier, he said.
“There are a lot of plans being developed as we speak about what is the next phase for this,” he said.
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