Synergizing energy storage with irrigation security: A novel irrigable PHES system and its comprehensive siting framework

Amid the global energy transition, the expansion of conventional pumped hydro energy storage is increasingly constrained by land availability. This is particularly pronounced in hilly areas, where potential storage sites often overlap with farmland experiencing irrigation scarcity, leading to significant competition between energy development and agricultural production. To address this water–energy nexus conflict, this study proposes an Irrigable Pumped Hydro Energy Storage (IPHES) system. By integrating energy storage with agricultural irrigation within a unified infrastructure, the system enables efficient dual use of land resources. An automated, demand-oriented siting framework is developed, departing from the conventional resource-centered logic. The framework prioritizes identifying irrigation demand, elevating irrigation security to the same decision level as energy storage benefits. To address spatial redundancy and resource competition in large-scale site selection, the framework also incorporates a spatial topology optimization procedure to ensure globally optimal site allocation. Using six provinces in southwest China as a case study, the framework identifies 783 optimal sites from approximately 297,395 candidates. The results indicate that IPHES achieves a mean levelized cost of storage of 0.116 USD/kWh, while each site provides irrigation area for a mean of 682 ha. Case-based verification confirms high water supply reliability and ecological sustainability, even under extreme drought conditions. These findings demonstrate that the proposed system represents a viable multifunctional infrastructure that synergistically enhances energy flexibility and agricultural water security.