LG&E and KU Energy operates Kentucky's first and largest utility-scale energy storage system — a 1-megawatt, 2-megawatt-hour lithium-ion battery. The battery is co-located with E.W. Brown Solar, allowing the company to explore how batteries can improve the inherent intermittency of solar power.

The battery is operated 24/7, 365 days a year and is continuously collecting data — typically charging during the day when solar power is available and discharging at night. Battery use and availability has improved — from 54% in 2018 to 89% in 2020. The battery has collected twice as much data and stored almost twice as many megawatt-hours in 2020 as any other year.

Modes of Operation

The battery can be operated in several different modes. The Technology Research and Analysis (TRA) department most commonly operates the battery with Target State of Charge (SOC), which charges or discharges the battery to a certain percentage of capacity. The SOC% is programmed to fluctuate between 11% and 89%, as the top and bottom 10% of capacity are withheld for safety.

Other advanced functions are Auto Volt-Var, during which the battery supplies or absorbs reactive power in order to maintain grid voltage at a reference value, and Auto Frequency Watt, in which the battery rapidly charges or discharges to reduce grid frequency variation. The battery is also capable of performing solar-supporting functions during the day, including power smoothing and peak limiting.

Monitoring the Battery

The TRA department developed a real-time battery performance dashboard to monitor the system and maintain awareness of hundreds of conditions remotely. The department also developed an alarm system, capable of emailing and texting staff to alert them immediately about potential problems at the battery site. Employees in the department rotate responsibility for operating, monitoring, and maintaining the system, and all are capable of responding to problems at the site.

Academic Publications

Researchers at the University of Kentucky working with subject matter experts at LG&E and KU have collaborated on multiple research topics related to solar and battery energy storage systems. Over the past three years, nine academic papers and presentations based on data retrieved from the E.W. Brown Solar Dashboard and E.W. Brown 1-megawatt, 2-megawatt-hour battery have been published in multiple international journals, including the distinguished IEEE Transaction for Industry Applications. Links to each of the academic publications are listed below.

Parameter Identification for Cells, Modules, Racks, and Battery for Utility-Scale Energy Storage Systems
O.M. Akeyo, V. Rallabandi, N. Jewell, A. Patrick, D.M. Ionel - IEEE Access 8, 215817-215826

The Design and Analysis of Large Solar PV Farm Configurations With DC-Connected Battery Systems
O.M. Akeyo, V. Rallabandi, N. Jewell, D.M. Ionel - IEEE Transactions on Industry Applications 56 (3), 2903-2912

On the Control of a Solid State Transformer for Multi-MW Utility-Scale PV-Battery Systems
Y. Zhang, O.M. Akeyo, J. He, D.M. Ionel - 2019 IEEE Energy Conversion Congress and Exposition (ECCE), 6481-6486

Measurement and estimation of the equivalent circuit parameters for multi-MW battery systems
O.M. Akeyo, V. Rallabandi, N. Jewell, D.M. Ionel - 2019 IEEE Energy Conversion Congress and Exposition (ECCE), 2499-2504

Modeling and simulation of a utility-scale battery energy storage system
O.M. Akeyo, V. Rallabandi, N. Jewell, D.M. Ionel - 2019 IEEE Power & Energy Society General Meeting (PESGM), 1-5

Incorporating battery energy storage systems into multi-MW grid connected PV systems
V. Rallabandi, O.M. Akeyo, N. Jewell, D.M. Ionel - IEEE Transactions on Industry Applications 55 (1), 638-647

Power Utility Tests for Multi-MW High Energy Batteries
O.M. Akeyo, H. Gong, V. Rallabandi, N. Jewell, D.M. Ionel - 2018 7th International Conference on Renewable Energy Research and Applications, 1396-1399

Improving the capacity factor and stability of multi-MW grid connected PV systems with results from a 1MW/2MWh battery demonstrator
O.M. Akeyo, V. Rallabandi, N. Jewell, D.M. Ionel - 2018 IEEE Energy Conversion Congress and Exposition (ECCE), 2504-2509