862 that regenerative conveying can recover a substantial fraction of gravitational energy but remains limited by frictional resistances and conversion losses (Mathaba & Xia, 2017; Jennings, 2020). The sensitivity analysis indicates that CB-GES is a strongly geometry-dominated technology, where the vertical drop (and corresponding belt inclination) is the most influential driver of both round-trip efficiency and regenerated power. Therefore, mine sites with steep ramps, benches, or waste-dump gradients are inherently advantaged, and practical deployment should prioritize locations where conveyor inclination can approach the maximum allowable slope for safe and stable material transport. Beyond geometry, the results show that electrical efficiency (motor/generator and drive) and mechanical efficiency (representing conveyor resistances) significantly influence round-trip performance. The optimised case demonstrates how targeted improvements can enhance storage effectiveness. The selection of 300 mm vertical drop, belt speed of 4 m/s, material load of 660 kg/m, electrical efficiency of 0.95, handling loss factor of 0.03, and mechanical efficiency of 0.91 results in a charging power of 9.16 MW, a regenerated power of 6.47 MW, and a round-trip efficiency of 0.71. These values closely match the improvement pathway suggested in the literature, where conventional conveyor-based storage is expected to be around ~60%, while low-rolling-resistance belts and low-friction idlers can elevate performance toward ~70% (Jennings, 2020). Notably, this places CB-GES below typical pumped hydro (often cited 75–85%) and lithium battery storage (85–90%), but the system compensates through mechanical simplicity, long service life, and the absence of storage self-discharge when material remains stockpiled. In terms of power controllability, the analysis indicates that CB-GES output can be regulated effectively by controlling belt speed and mass flow rate, enabling flexible ramping between operating points. This behaviour is particularly relevant for grid applications beyond bulk energy shifting. The inverter-based drives can adjust belt speed within seconds, allowing fast transitions between charge and discharge modes and rapid modulation of power. These features support peaking and potentially ancillary services such as ramping and frequency support. Such operational flexibility is consistent with the broader industrial deployment of regenerative drives in bulk conveying, where power-electronics-based control is central to stable downhill generation (Kawalec & Król, 2021; Mathaba & Xia, 2017). The system's scalability is also a major strength that emerges from the results, since the capacity of storage is determined primarily by the available height difference and the amount of material that can be transferred between stockpiles on a cyclical basis. Consequently, an increase in pile size results in an increase in energy capacity without necessitating a major redesign. For example, a 5 MW plant, can be sized for 4 hours continuous operation resulting in 20 MWh storage capacity or for 8 hours resulting in 40 MWh, by simply changing the stockpile capacity. Similarly, a 10 MW configuration can reach approximately 120 MWh over a period of 12 hours at rated power. Furthermore, the technical feasibility of multi-MW conveyors is substantiated by mining practice since conveying systems commonly transport 5,000–15,000 t/h, and individual regenerative conveyors have demonstrated generation capacity of 5–10 MW. Real-world examples further corroborate this scale, including the Los Pelambres downhill conveyor in Chile (~5.97 km length, ~535.8 m drop) reportedly generating about 9 MW. The results of the study indicate that CB-GES should be interpreted as a site-coupled infrastructure reuse pathway rather than a uniform ready-to-use energy storage solution. The most favourable outcomes occur in areas where steep topography, suitable geotechnical conditions and adequate stockpile areas coexist, conditions which are typical of large open-pit mines and their associated waste dumps. In this context, CBGES provides a reliable technical route for converting dormant mining assets into grid-supporting infrastructure, while simultaneously contributing to post-mining land rehabilitation strategies through productive reuse of disturbed landscapes. 6. CONCLUSIONS CB-GES represents a site-specific, infrastructure-reuse pathway for long-duration storage in postmining regions, particularly where steep topography and existing conveying systems are available. While efficiency is lower than batteries and pumped hydro, CB-GES offers advantages in mechanical simplicity, long lifetime, and independence from critical materials. Key limitations include dependence on favourable site geometry, sensitivity to frictional losses, and uncertainties related to material handling efficiency and long-term mechanical wear.
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