Improvements of the Ship Energy Efficiency by a Steam Powered Turbogenerator in LNG Propulsion Applications

This paper focuses on potential benefits due to the Waste Heat Recovery (WHR) from marine dual fuel engines. WHR solutions are usually adopted for the traditional diesel oil applications, while for gas fueled engines are currently under consideration (mainly due to the relatively high investment costs). In order to promote this ecofriendly technology within a marine hybrid propulsion system, it is important to assess the possible improvements in the ship energy efficiency, identifying an appropriate application and analyzing its overall performance level. Compared to traditional diesel oil, the use of the Liquefied Natural Gas (LNG) as fuel allows a better exploitation of the engine exhaust gas energy, resulting into a larger availability of steam for the surplus production of the ship electric energy. In order to evaluate the feasibility of an efficient WHR system in LNG propulsion applications, a numerical code representing the steam powered turbogenerator dynamics is presented. For the proposed case study, simulation results show a good behavior in the most critical electric load variations, confirming the correct sizing of the several WHR system components.