In what GE claims to be the largest gas turbine black-started by a modern battery, Entergy Louisiana has added a 7.4 MWh lithium-ion (nickel-magnesium-cobalt chemistry) unit at its Perryville power station to restart a 2001-vintage, 150-MW 7F.03 peaking gas turbine/generator should grid power be lost.
To re-energize the grid, black starts typically require separate gas or diesel generators to first start the larger generator. When you avoid a diesel generator, you also avoid other complications, especially the liquid fuel storage and delivery system. Also, black start assets typically are tested more than they are called upon to operate.
The 11-month project reflects several current trends. First is the growing and diverse grid-scale applications for large batteries, primarily lithium-ion. Second is the “hybrid” concept of pairing them with traditional generation and T&D assets. Many storage system engineers consider black start to be the most difficult grid-scale battery application.
According to GE specialists, the storage unit includes a grid-forming inverter, whereas most storage (and solar) assets employ grid-following inverters. The grid-forming inverter essentially creates a voltage source reference point the turbine can synchronize to. In other words, the inverter can operate in stand-alone mode, as its own grid.
“The voltage source inverter control is specifically designed to coordinate with the GT controls, in this case the familiar Mark VIe,” said Troy Miller, head of sales for GE Energy Storage, a subset of GE Renewable Energy Hybrids.
The battery system consists of three 40-ft shipping containers with 21,400 battery cells connected to a series of controls to convert DC power to AC.
GE expects interest in its hybrid storage solutions to grow, including solar, wind, and thermal plants, and even for competitor gas turbines. Earlier, GE pioneered the first commercial application of battery storage to LM6000 machines to convert a non-spin peaking unit into spinning reserve at Southern California Edison’s Center Peaking facility.
Entergy Louisiana declined to comment for this article, but was quoted in the GE press release on the project as follows: “This is an innovative use of battery technology that provides another tool to buttress the overall reliability and resiliency of our system.”
The utility’s 2019 Integrated Resource Plan noted that energy storage, particularly in the case of battery-enabled storage, provides a range of attributes including: The ability to store energy for later commitment and dispatch, ability to discharge in milliseconds and fast ramping capability, rapid construction (on the order of months), modular deployment, portability and capability to be redeployed in different areas, small footprint (allowing for flexible siting), and low round-trip losses compared to other storage technologies (such as compressed air). The IRP made no mention of the Perryville project.