Polymerelektrolyt-Brennstoffzellensystem für ein autonomes Unterwasserfahrzeug

The thesis deals with the design and build-up of a fuel cell system for an autonomous underwatervehicle (AUV). The utilized polymer electrolyte membrane fuel cell (PEMFC) is hybridized with the battery system in order to increase the mission duration and decrease the reloading time. The challenge in this work is to adapt the PEMFC system to a not foreseen environment while using a commercial fuel cell stack. In a first step, the boundary conditions for an operation under water and in the particular AUV have to be defined. In a second step, the development strategy has to be derived. In this sense, the state of the art of the individual subsystems is discussed. The most important system characteristic is the hindered mass transfer with the surrounding. As a result, a closed system with pure oxygen as an oxidant was developed. The inert gas intake, which resulted from impurities present in the gas bottles, had a strong influence on the design. As a consequence, operation time was reduced in a dead-end setup depending on the volume of the gas supply system. In the developed system an operation time of 1.8 hours was achieved. By using a recirculation on both gas sides the operation time could be further increased to a maximum of 71 hours. In the particular case, the available system volume was a restricting factor for the development of the system. The system volume was used as a primary design parameter. Afterwards, it was linked to further optimization parameters system stability, operation time and overall system efficiency. To reduce the system volume, gas conditioning was relinquished. The operation was validated by empiric measurements. Additionally, by using ejectors instead of compressors, the system volume could be reduced by 39 %.The influence of inert gases during dead-end operation of a closed fuel cell system was examined in an especially developed measuring setup. It could be shown, that a stable operation of the fuel cell system was possible up to an inert gas ratio of 3 %. With the designed dead-end-system a 24 hour operation was not possible. Therefore, gas recirculation was used on the cathodic as well as on the anodic side to allow a 24 hour operation. The developed system was assembled and tested in the laboratory. A stable operation of 8 hours was confirmed in an ex-situ measurement