A "megawatt-class" battery attached to American Electric Power's grid in Charleston, W.V. It's used as a buffer, able to generate a few hours of power for an overloaded substation.
These are sodium sulfur batteries from NGK Insulators of Japan. One of its battery purchases--part of a plan to buy 25 megawatts of storage this decade--will be used to store electricity generated by wind turbines next year.
These massive batteries don't come cheap. Installing three of them, capable of discharging 6 megawatts, will cost about $27 million. That's part of the reason that American Electric Power's use of storage on the grid is the exception, rather than the rule.
Photo by American Electric Power, Caption by Martin LaMonica
Source: cnet news