Recuperação de calor residual em motores Diesel GE 7FDL com foco em eficiência energética de locomotivas utilizando ciclo Rankine orgânico (ORC)

Abstract

The continuous growth of energy consumption and its consequences in terms of environmental impact is a reality in developed and developing countries and will be among the main challenges discussed in the coming years. On railroads, fuel consumption makes up the majority of operating costs. Thus, every opportunity for reduction, and the consequent savings generated, must be analyzed in detail. In addition, in response to a society increasingly concerned with the impacts caused by the exploration and use of fossil fuels, companies have sought solutions to better manage their energy sources and maximize their uses. In this way, the recovery of waste heat from internal combustion engines (ICE) of locomotives to generate electricity, aiming to reduce fuel consumption, reducing the emission of harmful gases, can become very attractive if implemented properly. In this context, the objective of this work was to verify the feasibility of recovering the residual heat from the ICE of a Dash-9 locomotive, equipped with a General Electric (GE) 7FDL engine, through an organic Rankine cycle (ORC) to reduce consumption of diesel. The study carried out through simulations, carried out in the Engineering Equation Solver (EES), found the ability to generate enough electrical energy to compose the need for the locomotive's electrical traction system. The results also point to the technical feasibility for the implementation of the ORC, with recovery of heat rejected by the cooling systems and exhaust gases of the IEC. It was found that an ORC with a simple arrangement, using the water from the cooling system as a heat source and using the fluid R134a, is able to provide a fuel economy that can reach 9.16%. Considering the same type of simple ORC arrangement, but using the heat from the exhaust gases of the ICE with the fluid R245fa, 136.9 kW of mechanical power and a specific cost of US$ 6,599.00 per kW generated were obtained. The ORC arrangement with preheating, using R245fa fluid, also presented the best results, not only for power, providing 288.6 kW, but also for the specific cost, of US$ 1,881.00 per kW generated. Regarding the economic viability of the project due to the reduction of diesel consumption, this last configuration, which led to more attractive results, equivalent to 3.24% for the internal rate of return and time to return on invested capital of 20, 2 years. Even after a sensitivity analysis of the economic viability of the project in relation to the price of diesel and the exchange rate of the Dollar, in the current conditions of equipment costs, none of the ORC arrangements studied presented results that adhered to the indicators adopted for new projects in the VLI, that are, a minimum rate of attractiveness of 17% and a payback period of less than 5 years.