Environmental-Based Working Fluid Selection for Organic Rankine Cycle for Waste Heat Recovery in Marine Diesel Engines

In the maritime sector, fossil fuels continue to dominate, and it is necessary to enhance energy efficiency and continue decarbonization processes. This study focuses on selecting optimal working fluids for Organic Rankine Cycle (ORC) systems integrated into a container marine diesel engine to recover waste heat from exhaust gases, scavenge air, and provide jacket cooling water. The selection process involved screening 168 pure and predefined mixture fluids from the REFPROP NIST database, focusing on criteria such as environmental properties, chemical reactivity, corrosivity, and thermal compatibility with the heat source. To assess the performance of the working fluids, energy, exergy, and exergo-economic analyses were conducted. The results indicate that Cyclopentane, Acetone, R1233zdE, and Methanol are the most efficient fluids for exhaust gas heat recovery. Simultaneously, cis-2-Butene and R510A exhibited excellent performance for scavenge and jacket cooling water applications. Additionally, the environmental impact assessment revealed that incorporating waste heat recovery (WHR) systems with the selected fluids significantly reduced CO₂ emissions and mitigated penalties under the FuelEU Maritime and EU ETS regulations. While it is anticipated that a total of 11 Million Euros will be saved from FuelEU and EU ETS penalties with the ORC system in 2050, approximately 40% of the ship annual fuel consumption will be recovered through ORC, with a 1.5-year payback period.