858 Figure 1-Principles of operation of conveyor belt-based energy storage system (CB-GES). At a system level, CB-GES performance is governed by three dominant mechanisms: (i) gravitational potential driven by vertical drop and transported mass, (ii) cumulative mechanical resistances along the conveyor system, and (iii) electro-mechanical conversion efficiency. The modelling framework therefore focuses on quantifying the balance between these three components, allowing rapid identification of favourable site geometries and design configurations before introducing detailed formulations. In ideal form, the stored energy is given by the gravitational potential energy E=mgH, where m is the lifted mass, g is gravitational acceleration, and H is the vertical height difference between stockpiles. For continuous operation, the available mechanical power associated with vertical transport becomes Pgrav=m,gH, where m, is the mass flow rate. In charging mode, the electrical input must overcome both the lift requirement and the conveyor resistances, which include rolling resistance at idlers, belt indentation losses, pulley losses, and skirt/transfer friction. These effects are typically represented through an equivalent resistance or aggregate friction term, consistent with the literature on conveyor energy modelling and efficiency optimization (Zhang & Xia, 2011). Accordingly, charging power can be expressed as the sum of the gravitational lift term and the resistive loss term, divided by motor-drive efficiency. In discharging mode, the conveyor operates as a generator when gravity provides surplus mechanical power beyond the total motion resistances. 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. Round-trip 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 postmining 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 round-trip efficiency of 0.60. These results are consistent with earlier conveyor-energy-storage assessments suggesting that conventional
RkJQdWJsaXNoZXIy MTM0Mzk2