Review on renewable energy systems of unmanned marine vehicles and guidance for energy selection

In recent years, the demand for unmanned marine vehicles (UMVs) has grown rapidly across various fields, and the energy supply for these vehicles has emerged as a key challenge that limits their endurance and operational range. The abundant marine renewable energies present a promising solution to this problem, but single renewable energy systems are insufficient for the long-endurance operational demands of UMVs in complex ocean environments. In this case, hybrid renewable energy systems have become a promising alternative. This paper undertakes a comprehensive review on the renewable energy systems of UMVs and explores the advantages and limitations of various energy combinations, involving solar energy, wave energy, wind energy, thermal energy, pressure potential energy, etc. The multi-criteria decision analysis method is introduced for optimizing the energy selection for UMVs, with decision-making guidance for the most suitable energy solutions of different UMVs. The findings suggest that the solar-wave combination is ideal for unmanned surface vehicles, while the solar-thermal energy-pressure potential combination is more suitable for unmanned underwater vehicles. This study offers a systematic framework for decision-making of the UMV energy system, which advances the application of marine renewable energies and provides theoretical guidance for practical decision-making in the future.