Research progress and prospect of fuel cell energy systems for marine and underwater applications

In the marine field，there is an increasing demand for energy systems that improve energy efficiency and reduce emissions. This need is particularly important for underwater energy systems，which require greater endur⁃ ance and stealth. Fuel cells，known for their high efficiency，low noise，minimal vibration，and low emissions，are well suited to meet these requirements. They can effectively address the improvement needs of marine and underwa⁃ ter energy systems，making them a promising technological direction. Currently，fuel cells have been introduced in both marine and underwater fields，and advanced fuel cell energy systems have been the focus of extensive re⁃ search. However，there are several challenges that need to be addressed. Therefore，this paper reviews the devel⁃ opment background and practical application status of marine and underwater fuel cell energy systems，introduces the frontier research progress of advanced fuel cell energy systems，and discusses key technical challenges such as hydrogen source technology，system integration，and environmental adaptability. Comprehensive analysis indi⁃ cates that fuel cell systems and their hybrid systems are expected to become the preferred solutions for future ma⁃ rine and underwater energy systems.