An innovative approach for optimal selection of pumped hydro energy storage systems to foster sustainable energy integration

The use of macro storage technologies has been widely studied in the literature with pumped hydro energy storage (PHES) emerging as the main option for its high stability and low environmental impact. Additionally, in recent years researchers have focused on combining a micro storage system with a photovoltaic and/or wind system that serves to increase self-consumption thereby reducing the load on the power grid. However, the selection of optimal micro system remains an open issue. This study thus proposes a methodology for selecting the optimal PHES system based on energy and economic analyses. The methodology was validated through a case study involving university buildings (University of Sannio) in Benevento - Italy, in which a photovoltaic system with peak power of about 142 kW was considered. The results obtained through a sensitivity analysis varying the total volume of reservoirs, showed an effective reduction in energy purchased from and sold to the grid. Subsequently the use of PHES system was compared with battery-based storage, commonly installed in building application. The energy produced from renewable sources delivered to the building increased by 25 % and 13 % for battery energy storage system (BESS) and PHES system, respectively. The economic analysis demonstrated the BESS to be most cost effective with a minimum levelized cost of storage of about 158 €/MWh, while the pumped hydro energy system showed attractive economic results only when the investment costs exclude the reservoirs (levelized cost of storage was 136.5 €/MWh).