Thermo-economic analysis and environmental aspects of absorption refrigeration unit operation onboard marine vehicles: RO- PAX vessel case study

Marine diesel engines lose a huge amount of fuel heat content in the form of exhaust gas and jacket cooling water, especially onboard high-powered marine vehicles such as Ro-Pax ships. In this paper, the possibility of using the waste heat of marine diesel engines as a source of heat for air conditioning absorption system is investigated. The thermodynamic analysis, in addition to the environmental and economic analysis of the air condition absorption cycle operated with two heat sources using lithium bromide as absorbent, are performed using the Engineering Equation Solver (EES) software. The last 10 years have seen a steady growth in the passenger ferry and Ro-Pax market, with particularly strong growth in passenger numbers. As a case study, a Ro-Pax vessel operating in the Red Sea area is considered, regarding the profitability of using air conditioning absorption system. The results show specific economic benefits of the jacket cooling water operated absorption refrigeration unit (ARU) over the exhaust gas operated unit, with annual costs of capital money recovery of 51,870 $/year and 54,836 $/year, respectively. Environmentally, applying an ARU machine during cruising will reduce fuel consumption by 104 ton/year. This, in turn, will result in reducing NOx, SOx, and CO2 emissions with cost-effectiveness of 7.73 $/kg, 20.39 $/kg, and 0.13 $/kg, respectively.