Engineers at American Electric Power’s (AEP) research laboratory are testing a new stationary battery capable of storing large amounts of electrical energy for use during peak energy demand and for power quality applications. Such technology could provide relief from generation shortages and transmission constraints that lead to blackouts, curtailments and other power interruptions.
Tokyo Electric Power Company (TEPCO) and NGK Insulators Ltd. developed the high-density sodium-sulfur (NAS) battery during the 1980s. As part of that development, more than 20 NAS battery demonstrations have been installed in Japan, including two 6-MW plants at TEPCO stations. Each plant provides up to 48 MWh of energy storage for daily load leveling applications, which reduce the amount of generation needed during hours of peak usage.
As part of a joint effort with TEPCO and NGK to introduce the NAS battery technology in the United States, AEP is testing a 12.5-kW compact battery at the Dolan Technology Center. The experiment marks the first stationary battery application in the United States using sodium-sulfur battery technology.
Cost-effective bulk energy storage has often been referred to as the missing link in maximizing power delivery efficiencies. NAS technology can provide that link, said Dave Nichols, manager at Dolan. Cost and system compatibility issues are the major factors AEP will evaluate during the next several months, Nichols said.
“The battery is a new tool that we have to work with in the future to resolve energy delivery problems. It makes it feasible to utilize electrical energy storage on a much larger scale than in the past,” Nichols said.
Storing electrical energy is not a new idea and has been done with other technologies, such as flywheels, capacitors, lead acid batteries, compressed air and super conducting magnetic energy storage. AEP also has a pumped-storage hydroelectric project at its 605,000-kW Smith Mountain plant.
What makes the NAS battery technology revolutionary is its large energy density, high efficiency and long-term durability. The energy density of the NAS battery is three times larger than conventional lead acid batteries. The battery can be charged in eight hours, and its electrical energy can be discharged over a similar period or stored indefinitely if the temperature is maintained at 600 degrees Fahrenheit.
“The sodium-sulfur battery reduces the amount of generation and distribution and transmission infrastructure needed to meet peak demand,” Nichols said. “It can be used to deliver electricity into areas that previously had restrictions due to transmission or distribution constraints, and the battery can function as a standby source to protect against power disturbances.”
The NAS battery has been tested in Japan for load leveling applications, as an emergency power source and as a buffer for the unstable output of natural energy sources, such as wind and solar energy. The battery makes it possible to stabilize electricity demand, which fluctuates considerably between day and night. As a result, customers can reduce electricity bills.
By charging the battery during off-peak hours and using the electricity during peaks, an energy provider is able to operate its generation more efficiently. This process becomes economical to a customer if there is a big difference in the price of electricity between off-peak and peak times, if peak demand is reduced or if time of day pricing is implemented.
If testing is successful, the NAS battery will be installed later this year at another AEP location for peak shaving and emergencies. The goal is to offer the battery commercially in the United States in two to three years.