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AEP Milton NaS Battery Energy Storage System

Technology Type Sodium-sulfur Battery
Rated Power 2000 kW
URL More about AEP Milton NaS Battery Energy Storage System
AEP has pioneered the use of NaS batteries in the United States. Following testing at its Dolan Technology Center near Columbus, OH, the utility became the first U.S. electric company to deploy NaS batteries in 2002 when it installed and operated a 100 kW / 500 kVA demonstration unit in Gahanna, OH. In 2006, AEP installed a 1.2-MW stationary NaS battery near Charleston, WV. And in 2008, the utility installed three, 2 MW NaS batteries: one in Churubusco, IN.; one in Milton, WV; and one in Bluffton, OH. The 7.2 MW in NaS deployments are part of AEP’s electricity storage strategy that will also include transportable stationary batteries and distributed small scale energy storage systems. AEP deployed all of its NaS installations as a means to provide load leveling and alleviate transformer loading during summer peaks, defer capital upgrades, and offer emergency backup power to several hundred customers during electrical system outages. Ultimately, the NaS units offer AEP a degree of flexibility in determining the optimal approach for handling reliability problems. The units buy the utility time to decide whether to redesign a substation, build generation, or keep the storage units in place permanently. (All of the NaS systems are capable of being relocated for an estimated $85,000 to $115,000 if and when the company’s needs for storage change.) AEP’s 2-MW units were deployed in 2008, and are capable of providing islanding (backup power) for over seven hours when loss of utility power from the substation occurs. These newer installations can also perform load-triggered load leveling which, for example, allows the batteries to discharge just enough energy to hold a constrained substation transformer constant. As a result, a greater amount of energy can be reserved for islanding and battery life can be extended due to less frequent discharging. AEP uses an in-house SCADA system and developed custom software to control all of its batteries based on the loading transformer. The software essentially creates a feedback loop where the load of the transformer is compared to a desired maximum, and the battery output is then adjusted to achieve that maximum. In addition, the unit sited at the Balls Gap substation in Milton, WV successfully islanded approximately 700 customers for roughly 30 minutes during a simulated outage staged on July 8, 2009. A live islanding event, meanwhile, took place in December 2009, during a snowstorm that islanded 25 customers for two days. Over that period, the Milton installation was able to minimize disruptions; customers experienced less than three minutes of continuous disruption during the two-day outage period. Finally, on October 20, 2009, the Milton, WV battery was successfully operated to alleviate load and voltage concerns during a load transfer event between substations. While the transformer at one station was taken out of service for maintenance, load was transferred to a different station which caused voltage and loading concerns. The Milton battery was deployed and mitigated these concerns. Source: "Energy Storage and Project Demos" Electric Power Energy Research (EPRI)
This data has been validated by project staff through a review of publicly available information about the project, and verified by the project owner.
Project Status
Status Operational
Commissioning On 01.11.2008
Project Includes Multiple Systems No

2900 E Mud River Rd (Balls Gap Substation)
Milton, West Virginia 25541
United States

Utility American Electric Power
Utility Type Investor Owned
Paired Grid Resource Primary Distribution
Project Includes Multiple Systems No
Ownership & Value Chain Partners
Ownership Model Utility-Owned
Equity Owner 1 American Electric Power (AEP)
Equity Owner 1 Percent 100%
Energy Storage Technology Provider NGK Insulators Ltd.
Power Electronics Provider S&C Electric Company
Integrator Company S&C Electric Company
Developer American Electric Power (AEP)
Cost & Performance
Performance • System roundtrip AC efficiency: ~75% (Operational specifications can dramatically affect the overall efficiency; to extend the battery life, AEP utilized the DESS at 83% to 90% of its capacity during its first years of operation.) • NaS battery DC-DC efficiency: ~85% • PCS efficiency: ~95% (one-way)
Service Use Case Electric Energy Time Shift
Electric Supply Reserve Capacity - Spinning
Grid-Connected Residential (Reliability)
Transportable Transmission/Distribution Upgrade Deferral
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