Enhancing energy storage system evaluation in microgrids with high renewable energy penetration

Energy storage systems (ESS) are crucial in microgrids (MGs) with penetration, ensuring efficient energy management, mitigating intermittent generation, and maintaining grid stability. However, evaluating ESS effectiveness requires comprehensive metrics that consider both technical and economic aspects. Traditionally, ESS evaluation has focused on minimizing costs or enhancing reliability. This study introduces and formulates the Loss of Surplus Energy Rate (LSER) and Expected Loss of Surplus Energy (ELSE) indices as novel metrics to gauge ESS efficiency. Using probabilistic methods, we applied these indices to a high-penetration Renewable Energy Sources (RES) MG scenario, analyzing the performance of a Battery Energy Storage System (BESS) under various configurations. The study reveals that while traditional cost optimization suggests an optimal BESS capacity of 400 kW, the LSER and ELSE metrics indicate that a 450 kW BESS capacity more effectively minimizes surplus energy waste. Specifically, the LSER metric showed that increasing the BESS capacity from 400 kW to 450 kW reduces the loss of surplus energy from 0.43 to 0.28, translating to a significant improvement in energy utilization efficiency. These findings highlight a critical trade-off between economic factors and energy efficiency, suggesting that a nuanced approach considering both aspects can lead to more resilient and efficient MG systems in the era of heightened renewable energy integration.