Sarcouncil Journal of Engineering and Computer Sciences

Abstract: In the context of escalating fuel costs and stringent environmental regulations in agriculture, integrating waste heat recovery (WHR) systems into tractor engines represents a pivotal strategy for enhancing energy efficiency and sustainability. This study conducts a comprehensive theoretical assessment of a novel cascade system that combines a high-temperature steam Rankine Cycle (RC) with a low-temperature Organic Rankine Cycle (ORC) to harness exhaust and coolant waste heat from a 302 kW heavy-duty diesel engine typical in modern tractors. Employing thermodynamic modeling, advanced exergy analysis, and exergoeconomic evaluation, the system is optimized using multi-objective genetic algorithms to maximize exergy efficiency while minimizing specific electricity costs. Innovative aspects include the incorporation of a regenerative preheater in the ORC loop and the use of environmentally benign working fluids such as R1233zd(E) for the ORC and water-steam for the RC, selected based on global warming potential (GWP) and ozone depletion potential (ODP) criteria. Results indicate a net power output of 38.7 kW, an exergy efficiency of 42.8%, and a brake-specific fuel consumption (BSFC) reduction of 12.5%. Exergoeconomic analysis yields a unit cost of electricity at 16.85 USD/GJ, with a payback period of 3.5 years under variable load conditions. Sensitivity analysis reveals robustness against exhaust temperature fluctuations (400-550°C), and environmental impact assessment shows a CO2 emission reduction of 15.2 tons annually per tractor. Compared to single-loop systems, the cascade configuration improves overall efficiency by 18-22%, underscoring its innovative potential for off-highway applications. Future experimental validation is recommended to bridge theoretical insights with practical deployment.