Simulation of the use of Organic Rankine Cycle (ORC) to reduce fuel consumption in locomotives on Brazilian railroads 2022-36-0088

According to the International Energy Agency, of world energy consumption, fuel oil and natural coal, as primary sources of energy for some process, correspond to about 60% of the total. This consumption has been increasing for decades, mainly in the transport sector, including railways. In Brazil, in 2019, the transport sector represented 32.7% of energy consumption. At VLI Logística, a company that operates 7,000 km of railways in Brazil, consumption in 2020 was 203 million litres of diesel, which generated a cost of US$ 86 million. In this context, it is necessary to increase energy efficiency in the sector and, for this, the feasibility of recovering waste heat from the internal combustion engine (ICE) of a locomotive must be verified. The present study was carried out considering a GE 7FDL engine, 16 cylinders, turbocharged, with water cooling and 4,020 HP (2,998.92 kW) of power. The simulations of ORC cycles, using the cooling water system and the exhaust gases of the ICE, developed in the Engineering Equation Solver (EES), point to a heat recovery capacity that can generate up to 10% of the electrical power of the ICE, with the cooling water system generating 89.9 kW, and the exhaust gas system producing 271.9 kW. Applying an arrangement with preheating, using the 2 systems, the generated power reached 314.4 kW. Fuel savings can reach 9.44%, depending on the locomotive's operating time at each acceleration point. Regarding the economic viability, the internal rate of project return was 3.10%. The payback time on invested capital was 20.4 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, none of the ORC arrangements studied presented results that adhered to the indicators adopted for new projects in the VLI.