Evaluating Battery Energy Storage System (BESS) Sizing for Substation Investment Deferral Using Load Profile Analysis in Thailand

As Thailand's electricity demand continues to rise due to rapid economic and industrial development, there is a need to find new approaches to maintain grid stability and defer costly infrastructure investments. This study introduces a method to determine the optimal battery size for battery energy storage systems (BESS) in distributed substations, focusing on addressing peak demand exceeding transformer (TR) capacity. By analysing load profiles and growth rates, the method identifies the first year of overload, overload periods, and corresponding BESS capacity requirements. Key parameters, including the energy needed for discharging (Eneed) and energy available for charging (Eallow), were used to define the BESS size and optimize its operation based on electricity tariff periods in Thailand. Among different characteristics of load profile patterns, load profiles with a distinct difference between peak-time overload and off-peak low consumption demonstrated the greatest potential for delaying substation upgrades, enabling deferral periods of up to 9 years. In contrast, load profiles with flatter demand patterns exhibited limited potential for investment deferral. The finding highlights that BESS size is significantly influenced by the gradual decrease in Eallow and the increase in Eneed over time, driven by load growth. Future research should explore additional factors such as investment and maintenance costs, cost-benefit analyses, and alternative strategies to enhance substation investment deferral decisions.