Safety and CO2 emissions: Implications of using organic fluids in a ship's waste heat recovery system

This paper considers the practical application of exhaust gas waste heat recovery from the main engines of merchant ships. A water-based Rankine Cycle is used as a baseline and this is compared with five organic Rankine cycle systems using benzene, heptane, hexamethyldisiloxane, toluene and R245fa. The thermodynamic model of the waste heat recovery system is described. This is then applied in a case study utilising an Aframax tanker. The case study allows the comparison of the different waste heat recovery systems in more realistic scenarios. The efficiency of the different systems is compared as well as their potential to reduce CO2 emissions, ship impact, and economic viability are also discussed. The paper closes with consideration of the safety and regulatory issues associated with the use of organic fluids in the marine environment.