The efficiency and quietness of fuel cells make them attractive power sources for the autonomous underwater vehicles of the future. However, several technical issues must he addressed before fuel cells can surpass the performance characteristics of batteries, including efficiency, reliability, durability, standby operation and storage, changes to orientation, and high shock loads. Improvements to the storage of the fuel (hydrogen or hydrogen sources) and oxidizer (oxygen) make the biggest impact on the size, weight, and utilization of fuel cell systems.Proton-exchangemembrane fuel cells (PEMFCs) are the most attractive fuel cell system and already have been successfully demonstrated for use in Autonomous underwater Vehicles (AUVs). AUVs of the future may utilize directmethanol fuel cells @MFCs) o r solid-oxide fuel cells (SOFCs) which can use liquid methanol or diesel fuel instead of hydrogen.

The conversion of biogas to electricity presents an attractive niche application for solid oxide fuel cells (SOFCs). A number of attempts have been made to use biogas as a fuel for high temperature fuel cell systems such as SOFCs. Biogas can be converted to a hydrogen-rich fuel in a reforming process which can use steam or carbon dioxide as the reforming agent. Conventionally, the reforming process is conducted at around 850 • C using several different catalysts depending on application. Biogas naturally contains the reforming agent, carbon dioxide, however, for typical biogas the content of carbon dioxide is insufficient to conduct the reforming process safely. Fore those cases, steam is added to prevent carbon deposition. Carbon formation occurs between the catalyst and the metal support, creating fibers which damage the catalytic property of the reactor. A number of papers have dealt with the problem of carbon deposition during both methane steam reforming and dry reforming. However, from the standpoint of solid oxide fuel cells, not every carbon-free condition is optimal for its operation. This paper treats this subject, explaining the mechanism of carbon formation during the steam reforming of biogas and using a numerical analysis to determine efficient and carbon-free working conditions.

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