Energy, exergy and economy (3E) investigation of a SOFC-GT-ORC waste heat recovery system for green power ships

Abstract

Ships are moving land in the vast ocean and are an indispensable means of transportation for humanity. At present, green power systems and low-carbon fuels are the development trend of energy-saving, emission-reduction, and low-carbon consumption of green ships. However, existing ships have many waste heat emissions and considerable noise pollution from shipboard electromechanical equipment. Based on the above issues, this study combined SOFC (Solid Oxide Fuel Cells) with a GT (Gas Turbine) and ORC (Organic Rankine Cycle). It proposed a waste heat-driven composite energy recovery system for the green power ships. Based on the feasibility analysis of single SOFC performance and waste heat utilization, combined with GT-ORC system, the thermodynamic model construction, working medium selection, energy, exergy and economy (3E) analysis of the whole system are carried out. The result shows that among the effective energy destruction of the entire system, the endogenous effective energy loss accounts for 89.73%. The avoidable-endogenous energy destruction of GT accounted for 92.95%, which has a significant improvement in saving space. The investment cost of heat exchanger accounts for the highest proportion, which is 22.62%. Therefore, it is necessary to focus on strengthening the heat exchange process to reduce the investment cost. The evaporative pressure and isentropic efficiency seriously affect the investment ratio of the system, in which the investment of expander and working medium pump increases by 34.6% and 153.3%, respectively, within the allowable working conditions.