This is the same condition enabling energy recovery in regenerative conveyors used in mining haulage alternatives, where downhill operation can yield measurable net energy export (Kawalec et al., 2020). In CB-GES, the regenerated electrical output is calculated from the available gravitational power minus resistive losses, multiplied by the generator and power-electronics efficiency. Roundtrip efficiency is then obtained by combining charging and discharging efficiencies and is strongly governed by: (a) the vertical drop or inclination (which increases the gravity term), (b) frictional losses (which increase with conveyor length and operational conditions), and (c) the conversion efficiency of the motor–generator and inverter (Wang et al., 2025). It is evident that these loss mechanisms scale in a non-uniform manner with geometry and throughput. Consequently, the model is characteristically beneficial to sensitivity analysis and design optimization, thereby providing a quantitative approach for selecting mine sites and conveyor configurations that ensure maximum storage effectiveness while maintaining operational robustness. 3. SYSTEM PERFORMANCE MEASURES – SENSITIVITY ANALYSIS AND OPTIMIZATION To quantify the operational characteristics and the performance of a CB-GES system and identify the most influential design variables, two core measures were considered: (i) net electrical power in charging and discharging mode, and (ii) round-trip efficiency. The sensitivity analysis was used to investigate the effect of critical parameters such as the vertical drop (H), the belt speed and load and the mechanical and handling losses, on the regenerated power and round-trip efficiency. A baseline design case for conveyor length L=1000m illustrates typical system magnitudes for post-mining applications. With a vertical drop of approximately H=260m, belt speed v=2.5m/s, and material load q=530kg/m, the calculated electrical power required for charging is on the order of 4.2 MW, while the regenerated power in discharging is approximately 2.5 MW, yielding a roundtrip efficiency of 0.60. These results are consistent with earlier conveyor-energy-storage assessments suggesting that conventional conveyor technology enables around 60% round trip efficiency and that improved low-rolling-resistance belts and low-friction idlers can raise performance toward 70% (Jennings, 2020). Sensitivity analysis was implemented across representative ranges of system main parameters. The used ranges included vertical drop ranging from 100–300m, belt speed from 2–4 m/s, material load from 230–660 kg/m, motor–generator efficiency from 0.90–0.95, materialhandling loss factor from 0.03–0.07 and mechanical efficiency from 0.60–0.91. As indicated in Figure 2, the analysis confirms that vertical drop/conveyor inclination is the dominant driver of efficiency, because increasing inclination directly increases the gravity term relative to resistive losses. This aligns with conceptual CB-GES investigations in decommissioned pits, where geometry and slope are repeatedly identified as the governing constraints controlling both feasibility and energy recovery (Galetakis, 2023).
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