FROM PITS TO POWER: CONVEYOR-BELT GRAVITY ENERGY STORAGE FOR POST-MINING LANDSCAPES Michail Galetakis1*, Stella Raka1, Anthoula Vasileiou1, Foteini Stathogianni1, Przemysław Moczko2, Adam Bajcar3, Maria Lazar4, Marek Cała5 and Jan Burda6 1Technical University of Crete, Chania, Greece 2Wroclaw University of Science and Technology, Poland 3Poltegor Institute, Poland 4University of Petrosani, Romania 5AGH University of Science and Technology, Poland 6VUHU a.s. Czech Republic (*Presenting author: mgaletakis@tuc.gr) ABSTRACT This study presents the conceptual design and performance analysis of a Conveyor Beltbased Gravity Energy Storage (CB-GES) system, developed under the GRENMINE research project for energy storage applications in decommissioned mining areas. The CB-GES system leverages the existing steep topography and the availability of bulk granular materials (like sand, gravel, crushed rock) of former open-pit mines. The system stores energy as gravitational potential by using excess renewable electricity to power a reversible conveyor belt, transporting material uphill to an upper stockpile (charging mode). When power is needed, the process reverses and the descending material drives the motor-generator, feeding electricity back to the grid (discharging mode). System modeling and sensitivity analysis confirm that key parameters, particularly the vertical drop/conveyor inclination, friction losses, motor/generator efficiency and material load, significantly influence efficiency and output power. Optimized designs project a round-trip efficiency of approximately 60–70%, while the system is highly scalable, with capacity limited only by stockpile size and vertical difference, enabling long-duration storage and power ratings from a 1 to 10 Mw. The preliminary economic evaluation indicates that CB-GES is cost-competitive since new installations are estimated to have a Levelized Cost (LCOS) of stored energy from 100 – 200 €/Mwh, which is comparable to Lithium Iron Phosphate (LFP) batteries. Utilizing existing disused mine conveyors reduces the LCOS (80 - 170 €/Mwh), making it competitive with Pumped Hydro Storage (PHS) offering a sustainable solution for decommissioned mines. KEYWORDS Gravity energy storage, regenerative conveyor-belt, post-mining land reuse, energy storage performance, levelized cost of storage (LCOS) 1. INTRODUCTION The rapid growth of variable renewable energy is shifting power systems toward operating regimes where flexibility and long-duration energy storage become essential for reliability and cost control. International roadmaps increasingly emphasize storage deployment at scale, not only to smooth intraday variability but also to provide multi-hour to multi-day balancing and firming services (IEA, 2024). While lithium-ion batteries have dominated recent installations, policy and
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