Design and Development of a Smart Pumped Hydro Storage System Utilizing the Unused Solar PV Power Output

Abstract

The growing use of solar photovoltaic (PV) systems in decentralized energy setups has compounded issues related to intermittency, battery degradation, and the excessive curtailment of surplus generation. This study proposes and experimentally validates a smart hybrid energy storage architecture that integrates pumped hydro storage (PHS) with a PV–battery system to enhance energy management and lifecycle cost performance in rural electrification contexts. A case study was conducted for a rural household in Pakistan, near Kot Diji Fort, with an energy demand of 1754 Wh per day. The optimal size of the PV system was 400 Wp to ensure complete supply security. Extensive power management analysis showed a large mid-day surplus generation (456 Wh/day) due to battery saturation limitations. A closed-loop PHS subsystem was designed, constructed, and integrated to utilize this otherwise curtailed energy. When PV power was in excess, it was used to pump water during peak sunlight hours, and the stored gravitational potential energy was later converted into electricity during the evening peak period (7:00–9:00 PM). Experimental results established that PHS integration significantly reduced the battery depth of discharge, with the evening state-of-charge declining by only about 1%, thereby increasing battery service life. A comparative techno-economic analysis showed that a standalone PV–battery system has a levelized cost of energy of 33.24 PKR/kWh, whereas the integrated PV–battery–PHS system achieves a reduced cost of 27.56 PKR/kWh. The findings corroborate the claim that PHS hybridization improves renewable energy utilization, reduces lifecycle costs, and enhances storage resilience. The proposed framework offers a scalable and sustainable option for decentralized energy systems and supports increased renewable energy penetration with long-term energy security in off-grid and weak-grid areas.