Reformation of Jet Fuels for Navy Ground Cart Applications 2006-01-3095
Fuel cells have been under considerable interest for both commercial and military aviation applications for power generation needed for advanced computational and communication systems on board aircraft, as well as for other power requirements needed both while in flight and on the ground. However, in order to power the fuel cells, hydrogen must be generated at some point, the ideal source being the logistic fuels such as JP-5 or JP-8 that is already used for propulsion. This process is not trivial, as several potential issues can arise from processing logistic fuel, the two primary concerns being the effect of sulfur within the fuel on the processing and fuel cell components, and the longevity issues resulting from coke formation during fuel processing. In the first part of this paper, we look as work that we have performed that addresses some of these issues for the steam reforming of JP-5 to produce pure hydrogen for fuel cell use. Specifically, we have identified a means to separate the reforming process into several steps in order to minimize the amount and cost of maintenance that must be done on the system. This separation can potentially lead to other optimizations in the reforming pathway. Results from bench-scale demonstrations of these processing steps will be presented based on the conversion of JP-5 fuel.
In considering applications for this technology, a ground cart would likely be the first large scale target that can then be used to plan for other application areas. Present ground carts ranging from 90 to 300kVA power output are a critical tool for aviation support, but are presently based on the inefficient conversion of logistic fuels to power through internal combustion. It may be possible to replace the internals of a ground cart to use fuel cell to improve the efficiency of the energy conversion process, however, certain decisions will need to be made as to what processes will be retained on board the ground cart and which can be done at a central facility to support multiple ground carts. Three possible arrangements of equipment for ground carts based on logistic fuels can be identified:
The use of a hydrogen storage medium with hydrogen directly feed to the fuel cell. This option would require a stationary plant to generate hydrogen, most likely through the desulphurization and reforming of logistic fuels.
The use of on-board reforming of sulfur free logistic fuel, with the output sent to the fuel cell. A central plant to handle the sulfur removal of the fuel would be required.
The use of both on-board desulphurization and reforming of as-delivered logistic fuels, with the resulting output feed to the fuel cell. In this case, no additional support facilities would be needed.
In the second part of this paper, we examine each of the above scenarios in the consideration of replacing a current 90kVA combustion-based unit. System models have been built for fuel processing of JP-5 in order to size the individual processes within the ground cart and provide representative mock-ups of each arrangement. Other factors such as environmental, maintenance, and longevity have also been considered as part of this study. We have also considered the prospect of using other fuel cells besides PEM-based units as to determine if improvements in thermal and mass integration can be performed for each configuration. Additionally, we consider what the size of the off-board support systems would be to support a number of ground carts.