TVA Power-Storage Facility to Improve Power Reliability
February 28, 2003
To meet peak energy needs and improve power quality, the Tennessee Valley Authority (TVA) is building the nation's first large-scale, energy-storage facility north of Columbus, Mississippi. The plant, now under construction, will store electricity during off-peak periods, and retrieve it for use when the need for power increases or when a major TVA grid service line outage occurs affecting Columbus Air Force Base and 4-County Electric Power Association customers living near the base.
Located adjacent to Columbus Air Force Base, the facility is designed to store up to 120 megawatthours of energy. Once fully operational, it will be capable of providing power to approximately 7,500 homes for 10 hours or more. Construction is expected to be completed by the summer of 2003 with a start-up and testing period to follow. Designed and developed by Regenesys Technologies Limited of the United Kingdom, the plant's technology is based on regenerative cells that store energy through an electrochemical exchange process.
"This innovative energy-storage plant is designed to improve power reliability and customer service, have limited environmental impact, and contribute to economic growth for consumers in Mississippi and throughout the Tennessee Valley," said TVA Chairman Glenn McCullough, Jr. "TVA continues to set the pace for energy production and demonstrate its role as a national leader in the use of cutting-edge, 21st-century technologies."
The energy storage plant will store or release energy by means of a reversible electrochemical reaction between two salt solutions. The system will use electrolytes in concentrated solutions of sodium bromide and sodium polysulphide. During periods of low demand for electricity, the plant will be "charged" by a chemical process pulling power from the main TVA grid source. The process reverses itself to release and transmit the stored energy when demand for power rises.
Energy storage technology offers power supply flexibility, in addition to technical and financial benefits. The financial benefits accrue from more efficient use of plant generation, transmission, and distribution, and the technical benefits are derived from improved system performance. The demand for electric power can fluctuate widely from season to season and throughout the day. But peaks in energy demand may only last for a few hours in a year, yet power stations must maintain the capacity to meet the largest of these peaks. Typically, the average demand for electricity is about 60 percent of maximum demand. When backup-generating capacity is taken into account, the average utilization of power plants is only 50 percent of their capacity. One way to improve power plant utilization and reduce expensive backup and peaking capacity is through the storage of energy during periods of low demand for use during periods of high demand.
Stored energy would provide a reliable, near uninterruptible power source, improve power quality, and allow TVA to take advantage of storing energy during daily load cycles. The system would also improve utilization of power plants that are currently cycled on and off to meet fluctuations in demand. Readily available, stored electric power could also provide voltage support, frequency regulation, and almost instantaneous response to major power outages. Finally, this source could defer the need for system upgrades.
For Columbus Air Force Base, home to the 14th Flying Training Wing of Air Education and Training Command's 19th Air Force, keeping the base's flight simulator facility running smoothly is vital to the base's mission-critical operation. Pilot training is one of the primary missions of the base. The advanced flight simulators used in preparing pilots for duty are extremely sensitive to power voltage and phase-power quality. Interruptions in power to the simulators, as well as the base's Precision Measurement Equipment Laboratory, would result not only in system downtime, but lengthy and costly recalibration and system maintenance requirements. Keeping these facilities running smoothly with consistent power from the new TVA energy storage facility would allow the base to help provide the airpower needed for our national defense.
"This project will generate value for our customers by reducing the need for high-cost generation during times of peak use," said TVA Director Skila Harris. "It also helps us make more efficient use of available resources, demonstrating TVA's commitment to excellence in business performance and public service." The energy storage plant will be the second facility of this type in the world, and the first of its kind in the United States. The Regenesys Technologies' plant will have the largest regenerative electrochemical cells ever built and operationally used for prime power redundancy.