Techno-economic and environmental assessment of the applications of battery energy storage systems (BESS) in storage hydropower plants for flexible power regulation and hydropeaking effect mitigation

Hydropeaking caused by storage hydropower plants leads to abrupt variations in river discharge, which disrupt natural hydrological regimes and negatively impact aquatic ecosystems. In Switzerland, environmental regulations require mitigation measures to reduce these effects, typically through compensation basins. However, alternative solutions, such as integrating Battery Energy Storage Systems (BESS), offer innovative possibilities for hydropeaking mitigation. This study evaluates different scenarios combining storage hydropower plants with BESS, with or without compensation basins, to assess their feasibility and effectiveness in meeting environmental objectives. A 2D hydraulic model (HEC-RAS) was used to establish relationships between turbine discharge variations and river water level fluctuations. Based on these results, hydropeaking mitigation scenarios were defined and evaluated against key criteria : environmental performance, economic feasibility, operational flexibility, and water usage. The findings indicate that a hybrid operation of Francis turbines with BESS can significantly reduce the required volume of compensation basins, while a Pelton+BESS system without a basin approaches the required environmental thresholds. Moreover, the lifetime of the BESS is directly influenced by its charge/discharge conditions, highlighting the importance of optimized operational strategies.