Against this backdrop, alternative approaches that extend the applicability of pumped storage without fundamentally altering its operating principles are gaining attention. Engineering constraints and design optimisationMine-based pumped storage introduces a fundamentally different design envelope compared to conventional surface schemes. Within the wider energy storage ecosystem, mine-based pumped storage occupies a distinct niche. Looking ahead, Olrog sees mine-based storage as a way to expand the geographical reach of pumped storage hydro. In doing so, it may play an increasingly important role in addressing the growing demand for long-duration energy storage, particularly in regions where traditional pumped storage opportunities are limited.