component of material weight exceeds motion resistances (Kawalec et al., 2020). Modern industrial implementations commonly achieve regeneration via variable frequency drives using active frontend converters that support bidirectional power flow and stable control under generating conditions (Chelopo & Gupta, 2025). The feasibility of applying a reversible conveyor specifically as a storage plant in abandoned open pits has also been recently demonstrated conceptually, highlighting the relevance of slope angle, losses, and load throughput as critical design parameters (Galetakis et al., 2023). From a systems perspective, a CB-GES plant comprises: (i) an upper and lower storage area (stockpiles), (ii) a reversible conveyor line with mechanical support structure and idler sets, (iii) controlled loading/unloading equipment (feeders, hoppers, reclaimers), and (iv) an electromechanical conversion unit including motor–generator and power electronics for grid connection. The conveyor’s controllability is crucial since power output can be modulated by adjusting belt speed and the mass flow rate, allowing the plant to provide dispatchable services over a wide operating covering. However, the same controllability must maintain safe belt tensions, stable material transport, and acceptable braking behavior during transient events such as start/stop sequences, since dynamic stability is a known design challenge for downhill conveyors (Chelopo & Gupta, 2025). 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.
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