The widespread adoption of Battery Energy Storage Systems (BESS) is crucial for integrating intermittent renewable sources like solar and wind into the power grid, thereby advancing the goals of green energy. Deploying BESS underground offers a sustainable solution to land constraints and safety concerns. However, the dynamic and complex thermal environment underground severely challenges the accurate State-of-Charge (SOC) estimation, which is vital for the safety, longevity, and operational efficiency of BESS. Data-driven SOC models often suffer from performance degradation due to data distribution shifts caused by temperature fluctuations, especially when operational data for specific unde... More >