Waste Heat Recovery System Performance Analysis Using Organic Rankine Cycle for Marine Applications

The maritime industry faces stringent decarbonization targets, with waste heat from marine diesel engines representing a substantial untapped energy resource amounting to 50-65% of fuel input. This study presents a comprehensive thermodynamic and exergoeconomic analysis of an Organic Rankine Cycle (ORC) system integrated with a large marine two-stroke diesel engine for waste heat recovery. A distributed-parameter model of the ORC system is developed in MATLAB, incorporating realistic heat source characteristics from main engine exhaust gases (250-350°C) and jacket cooling water (80-90°C). Working fluid selection is optimized among R245fa, R1233zd(E), and R134a based on thermodynamic performance, environmental impact (GWP/ODP), and safety considerations for marine applications. The system achieves net power output of 487 kW, representing 6.8% improvement in overall engine efficiency, with exergy efficiency of 52.3%. Exergy destruction analysis identifies the evaporator (38.7%) and condenser (24.3%) as primary loss locations. Economic analysis reveals a payback period of 4.2 years at current fuel prices, with CO2 emission reduction of 2,850 tonnes annually. The novelty lies in marine-specific optimization considering confined installation spaces, variable engine loads under real operating profiles, and integration with existing ship systems. Results demonstrate that ORC-based WHRS offers a viable pathway for EEDI Phase 3 compliance and operational carbon intensity reduction for existing vessel retrofits.