Case Study of a Solar-plus-storage Hybrid Generation Plant for Georgia’s Electric Cooperatives

Grid-connected energy storage offers multiple advantages to power grid operators who strive to optimize the use of renewable generation assets and solve operational issues that occur with higher renewable penetration. Due to the declining cost of battery cell technologies, battery energy storage systems (BESSs) are being deployed across the country. Electric Membership Cooperatives (EMCs) in Georgia are interested in BESS capabilities as distributed energy resources and as a means to complement utility-scale solar generation as they strive to meet the demands of a transitioning energy landscape. As a research and development project, Green Power EMC, the not-for-profit electric cooperative that secures renewable energy resources for 38 Georgia EMCs, has commissioned and now operates a 250 kW/548 kWh BESS paired with a 1 MW solar generation facility located on one of their member cooperative’s feeder near an industrial load. Proving the methods for design, testing, control, and maintenance at a scaled-down site is necessary before investment of grid-impactful storage systems is required to facilitate higher levels of intermittent renewable resources at the transmission and distribution level. A novel plant controller was implemented to demonstrate the following modes of operation: peak demand reduction, retail rate reduction, and solar intermittency control. Despite a distribution interconnection, the plant is operated with standard transmission equipment with connection to the statewide SCADA system for real-time data of operating parameters and battery diagnostics. The paper describes the present progress and lessons learned from this project thus-far with analysis of the plant’s operational data.