An early-stage approach to optimise the synthesis, design and operation of a marine energy system for liquefied natural gas carriers

Abstract

Since decisions of the greatest impact are made in early stages of ship design, developing design tools to make more information available sooner is desirable. Moreover, there is still room for improvements on the optimisation of energy system selection considering an integrated approach. Therefore, the present work aims to provide a comprehensive early-stage approach to perform the optimisation of design, synthesis and operation, considering economic and technical aspects as well as route weather. Constraints are used to avoid propellers that could present issues concerning strength, cavitation and vibration. Various propellers, sixteen engines and four operational profiles are assessed. A differential evolution optimisation algorithm whose objective function to be maximised is the net present value is applied. The case study is designed using a liquefied natural gas carrier of 175,000 m3 sailing between Lake Charles (USA) and Tokyo Bay (Japan), via Panama Canal. All suitable matchings for 15,023 propellers are found. The approach shows a gain of 22% between the worst individual of the initial population and the worst individual of the final population. The required brake power is approximately 22% higher for rough weather than for still water. A difference of over 120% was found by comparing varied matchings of economic scenes and fuel profiles. The approach shows a significant gain and highlights the value of exploring a broad range of energy system configurations in an integrated manner, considering the weather condition.