Preliminary Technical and Pumping-Energy Assessment of an Underground Pumped-Storage Hydropower System Using a Post-Mining Shaft as the Lower Reservoir

The reuse of post-mining infrastructure for pumped-storage hydropower may reduce new underground construction while supporting the repurposing of decommissioned mines. This study presents a site-specific preliminary technical and pumping-energy assessment of an underground pumped-storage system using Budryk Shaft II as the lower reservoir. The assessment integrated shaft geometry, hydraulic conditions, turbine–generator selection, pressure-pipeline configuration, structural adaptation, hydraulic isolation, and staged water return. A working water volume of 12,000 m3 was adopted. The proposed generation unit comprises a vertical Pelton turbine operating at a gross design head of 900 m, a rated net head of 837.81 m, and a discharge of 0.71 m3/s. The rated turbine output is 5287 kW, and the turbine is coupled to a 6.3 kV synchronous generator. The three-stage pumping calculation yielded energy demands of 7.037, 19.600, and 37.371 MWh, giving a total of 64.008 MWh. These values are calculation-based estimates derived from the listed nominal pump capacities and powers using a simplified proportional power–flow assumption. At the rated turbine output, the calculated generation time of 4.695 h corresponds to 24.822 MWh of mechanical energy at the turbine shaft. Because verified generator-efficiency data are unavailable, the generated electrical energy and electrical round-trip efficiency cannot be determined exactly. The ratio of turbine-shaft energy to the calculated pumping-energy demand gives an upper-bound energy-return indicator of approximately 38.8%. Further work must verify pump operating points, generator performance, hydraulic transients, structural integrity, shaft sealing, auxiliary-energy demand, and the complete hydraulic connection to the upper reservoir.