Sustainable energy design of cruise ships through dynamic simulations: Multi-objective optimization for waste heat recovery

Modern cruise ships are energivorous systems and their design is challenging due to stringent restrictions on the environmental impact recently imposed by the International Maritime Organization. Nowadays, energy saving technologies and strategies for ships can be selected and analysed by means of system dynamic simulations. In this paper this innovative goal is obtained through TRNSYS where the ship-envelope and the related energy system are modelled and simulated by means of new customized weather data with the aim to optimize the system energy performance by considering different objective function (maximum energy saving, minimum payback, etc.). To show the effectiveness of the proposed approach, a novel case study is presented. It refers to a modern cruise ship fuelled by liquefied natural gas cruising in Mediterranean and Caribbean seas. Novel hourly weather files are developed for accounting actual locations and orientations of the moving ship. Low-, mediumand high-temperature engines waste heat recoveries are exploited for supplying different thermally activated energy saving devices. Results of the conducted optimization procedure show significant reductions of fuel consumption (between 0.1 and 1.9 kt/y), operating costs (up to 615 k(sic)/y), and pollutant emissions with respect to traditional systems. Short paybacks are obtained (lower than 5 years), depending on the considered innovative system layouts. Finally, useful design and operating criteria for ship manufacturers and users are provided.