Integration of battery and hydrogen energy storage systems with small-scale hydropower plants in off-grid local energy communities

The energy transition is pushing towards a considerable diffusion of local energy communities based on renewable energy systems and coupled with energy storage systems or energy vectors to provide independence from fossil fuels and limit carbon emissions. Indeed, the variable and intermittent nature of renewables make them inadequate to satisfy the end-users’ electricity demand throughout the whole day; thus, the study of energy storage systems, considering their seasonal storage behaviour (e.g., energy-power coupling, self-discharge loss, and minimum state of charge) is fundamental to guarantee the proper energy coverage. This work aims at identifying the off-grid operation of a local energy community powered by a 220 kW small-scale hydropower plant in the center of Italy using either a battery energy storage system or a hydrogen one with the Calliope framework. Results show that, whereas the hydrogen storage system is composed of a 137 kW electrolyser, a 41 kW fuel cell, and a storage of 5247 kgH2, a battery system storage system would have a capacity of 280 MWh. Even though the battery storage has a better round-trip efficiency, its self-discharge loss and minimum state of charge limitation involve a discharging phase with a steeper slope, thus requiring considerable economic investments because of the high energy-to-power ratio.