Towards a more efficient sailing: guidelines in the design and refurbishment process

The shipping industry, including passenger and merchant ships, is a significant contributor to global greenhouse gas emissions. To reduce these emissions, the use of high efficiency technologies on ships should be explored to define the best configuration for the design or refurbishment process in order to reduce the energetic, environmental and economic impact. However, due to the complexity of on-board ships’ energy systems and to the operating and climate conditions, different configurations could be considered for the reduction of energy consumptions due to electrical and thermal needs. With the aim of providing guidelines to maritime stakeholders in the energy system decision making process – relative to the construction and management of ships systems - a methodology for swift evaluation of the impact of high efficiency technologies on the energy performance of several types of ships and climate zones is developed. In this regard, the investigated technologies include Organic Rankine Cycle (ORC) machines and steam turbines, whose impact on the ships’ energy balance is explored by mean of the dynamic simulation approach. Each technology is applied to 2 different types of cruise ship; numerous navigation routes are explored in order to find out the optimal system configuration according to the external climate conditions. The proposed methodology exploits the use of dynamic simulations for the system optimization, applied to the complex energy system of ships, and the use of data analysis techniques. To this aim, dynamic simulation tools, developed in MATLAB and TRNSYS, are developed for the simulation of the waste heat recovery systems of the investigated ships. The goal of the study is to derive energy performance matrices to be useful for stakeholders for the swift identification of the optimal possible technologies to be considered for refurbishment or novel design aims. Preliminary results show that ORC machines are more feasible in colder climate zones; such considerations are reported for different technologies and climate conditions to highlight the more performing energy systems as the reference ship and climatic zone vary.