The European power system is facing an increasing need for flexible and long‑term sustainable energy storage technologies due to the rapid expansion of renewable energy sources. Small pumped‑hydro storage systems (SPHS) represent a promising solution, particularly when installed in post‑mining landscapes where existing residual open‑pit voids can be utilised and environmental impacts minimized.. The HYDROMINE project focuses on developing a replicable small‑scale PHS technology that integrates pump‑as‑turbine (PAT) reversible hydraulic machines, bio‑based polyethylene pipeline systems, geotechnical and hydrogeological modelling, and a multi‑criteria site assessment methodology. \r\nIn 2025, three representative sites in the Most Basin were analysed in detail, with the Vršany locality identified as the most suitable for a demonstration unit due to its favourable head, advantageous geotechnical conditions, and available infrastructure. \r\nAt the same time, the hydraulic characteristics of the PAT units were optimized using CFD simulations, control strategies eliminating water‑hammer effects were designed, and structural parameters of the bio‑based pipeline system were defined. Integrated modelling confirmed the technical feasibility of the system and its potential for deployment in other European post‑coal regions. The project results demonstrate that small‑scale PHS technology can significantly enhance power‑system flexibility, stabilise local distribution networks, and support the sustainable evelopment of regions undergoing transition after coal mining.

Keywords: pumped‑storage; hydropower; energy; storage; post‑mining; landscape; pump‑as‑turbine (PAT); bio‑based polyethylene; geotechnics; CFD simulations; energy transition; demonstration unit; flexibility