Optimal Energy Storage Sizing With Battery Augmentation for Renewable-Plus-Storage Power Plants

The renewable-plus-storage power plant is becoming economically viable for power producers given the maturing technology and continued cost reduction. However, as batteries and power conversion systems remain costly, the power plant profitability depends on the capacity determination of the battery energy storage system (BESS). This study explored an approach for optimal capacity determination of a BESS combined with renewable energy considering the complex degradation of lithium-ion batteries. The proposed sizing algorithm iteratively evaluates the effect of BESS operation on battery degradation and estimates the cash flows of the power plant. In addition, we studied battery augmentation that adds the storage capacity in the base system to sustain the BESS capacity throughout the project planning horizon. Using data from South Korea, we showed that both the optimal storage capacity and project profitability are higher when the BESS is combined with solar generation than when combined with wind generation. Moreover, simulation results demonstrated that the proposed battery augmentation scheme improves the project profitability by deferring the upfront cost of batteries and increasing the total revenue. The proposed approach can provide a comprehensive framework for the parties involved in a BESS project to accurately calculate the BESS sizes and maximize the project profitability.