Sizing the energy system on long-range AUV

Autonomous Underwater Vehicles (AUVs) can be used for various types of unmanned missions. Currently, the most common energy storage technique is rechargeable batteries. In order to increase the range and endurance of these vehicles, where volume is a limiting factor, fuel cell systems could offer a very attractive solution. Fuel cell systems can have a drastically increased specific energy compared to batteries and are now starting to become well developed technologies. However, in an underwater environment, both hydrogen and oxygen needs to be stored for the fuel cell. This study presents a sizing tool that compares the weight and volume to balance fuel cell and battery energy storage solutions for some selected AUV missions. The main result is the shifting point between batteries and hybrid battery/fuel cell system in terms of volume efficiency, where longer missions favor the latter.