Fuel Cells in Practice: Challenges and Benefits for AUVs

This study focuses on the feasibility and benefits of implementing of a fuel cell/battery hybrid power system in the autonomous underwater vehicle LoLo. We highlight the practical implications and challenges related to such a power system conversion and compare the benefits of using a fuel cell system rather than a pure battery system. Storage of hydrogen and oxygen as pressurized gases is considered most suitable for a conversion of this kind. In order to outperform Li-ion battery packs, high-pressure gas storage is required, preferably at pressures of 500 MPa or higher. Through a market analysis, we analyze the performance of commercial gas cylinders in terms of volumetric and gravimetric densities. This information can subsequently be used to compare energy density and effective energy density for the respective power systems. The study exemplifies how fuel cell/battery hybrid systems can provide up to 75% higher effective energy density compared to conventional battery packs. Ongoing developments in the fuel cell and auxiliary system markets are likely to allow for further optimization of the fuel cell system.