Diesel-electric locomotives remain the backbone of freight rail transport in Zambia. However, ageing fleets operating under low-speed duty cycles suffer from high fuel consumption and inefficient dissipation of braking energy. This paper investigates a battery-assisted hybridization strategy focused on regenerative braking energy recovery for Zambia Railways Limited (ZRL) diesel-electric locomotives operating along the 890 km Kitwe–Livingstone corridor. A MATLAB/Simulink co-simulation framework integrating traction demand, route gradients, battery dynamics, diesel fuel mapping, and a rule-based energy management strategy is developed and calibrated to ZRL operating conditions. A 7.5 MWh lithium iron phosphate (LFP) Battery Energy Storage System (BESS) installed on a tender wagon is evaluated based on realistic regenerative energy availability and State-of-Charge constraints. Simulation results indicate that regenerative braking capture and traction power smoothing reduce diesel fuel consumption by 15.4% per trip. The associated fuel cost savings demonstrate economic viability under conservative assumptions and can be reinvested into rail infrastructure and rolling stock maintenance, supporting improved operational reliability. The findings show that regenerative hybridization alone offer a practical, infrastructure-light pathway for improving energy efficiency and reducing fuel dependence on moderate-gradient freight corridors in developing railway networks.

This paper developed a Zambia Railways Limited (ZRL)–calibrated MATLAB/Simulink co-simulation framework to evaluate a tender-mounted 7.5 MWh Lithium Iron Phosphate (LFP) Battery Energy Storage System (BESS) retrofit for diesel-electric freight locomotives operating on the Kitwe–Livingstone corridor. Simulation results show that regenerative braking yields an average diesel fuel reduction of 15.4% over the representative 890 km duty cycle, despite the moderate gradients and low-speed operating conditions characteristic of the route. The selected BESS capacity was shown to be sufficient to absorb peak downhill regenerative energy while maintaining battery State-of-Charge (SOC) within safe operating limits, validating the route-specific sizing approach adopted in this study. The associated fuel cost savings translate into economically viable payback periods of 4.2 years and returns on investment of 24% under conservative assumptions, making regenerative hybridization suitable for deployment in capital-constrained operating environments. Importantly, the fuel savings achieved through regen braking can be redirected toward the maintenance of rail infrastructure and rolling stock, supporting improved track condition, locomotive availability, and long-term operational reliability at ZRL. In conclusion, the findings establish regenerative braking–based hybridization as a practical, infrastructure-light transitional pathway for reducing fuel dependence and emissions in ageing diesel-electric freight fleets, without requiring network electrification or changes to existing operational practices.

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