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Developing design tools to make more information available sooner is desirable because decisions of the greatest impact are made in early stages of ship design. Moreover, there is still room for improvement in the optimisation of energy system selection considering an integrated approach. Therefore, the present work aims to provide a comprehensive early-stage approach to optimise the design, synthesis and operation of a marine energy system for liquified gas carriers, considering their economic and technical aspects, and also weather along the route. Constraints are used to avoid propellers that could present issues concerning strength, cavitation and vibration. Various propellers, engines and operational profiles can be assessed with this approach. A differential evolution optimisation algorithm that maximises the net present value is applied. This part of the study details the approach that we have developed, while the case study, results and discussion, and the main conclusions are given in Part B. Different parameters can be set up in each route-track, which enables various operational profiles and sea conditions to be considered to seek the highest net present value. The proposed approach is expected to be able to automatically search a broad range of possible alternatives and then make small refinements to achieve the optimal arrangement.

The present work aims to provide a comprehensive early-stage approach to optimise the design, synthesis and operation of a marine energy system for liquified gas carriers, considering their economic and technical aspects, and also weather along the route. Part A of this work details the approach that we have developed while Part B will summarise the first part, it will then describe the case study, results and discussion, as well as the conclusion. Various propellers, 16 engines and 4 operational profiles are assessed. In this part, we will apply a differential evolution optimisation algorithm, whose objective function will be maximised as the net present value. The case study is designed to use a liquefied natural gas carrier of 175,000 m3 sailing between Lake Charles (USA) and Tokyo Bay (Japan), via the Panama Canal. All of the suitable matchings for 15,023 propellers are found. This 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 scenarios and fuel profiles. Our approach shows a significant gain and highlights the value of exploring a broad range of energy system configurations in an integrated manner, especially considering the weather conditions.