Abstract
A complete fuel cell-based auxiliary power unit in the 7.5 kWe power class utilizing diesel fuel was developed in accordance with the power density and start-up targets defined by the U.S. Department of Energy. The system includes a highly-integrated fuel processor with multifunctional reactors to facilitate autothermal reforming, the water-gas shift reaction, and catalytic combustion. It was designed with the help of process analyses, on the basis of which two commercial, high-temperature PEFC stacks and balance of plant components were selected. The complete system was packaged, which resulted in a volume of 187.5 l. After achieving a stable and reproducible stack performance based on a modified break-in procedure, a maximum power of 3.3 kWe was demonstrated in a single stack. Despite the strong deviation from design points resulting from a malfunctioning stack, all system functions could be validated. By scaling-up the performance of the functioning stack to the level of two stacks, a power density of 35 We l−1 could be estimated, which is close to the 40 We l−1 target. Furthermore, the start-up time could be reduced to less than 22 min, which exceeds the 30 min target. These results may bring diesel-based fuel cell auxiliary power units a step closer to use in real applications, which is supported by the demonstrated indicators.
Highlights
The results suggest that a long downtime prior to operation beginning, which is on the order of years in this case, must be avoided
A complete fuel cell auxiliary power unit operating on diesel fuel was developed and tested
Despite a malfunctioning stack and the resulting deviations from the design parameters, it was possible to take the system into operation and achieve a stable and reproducible stack and system performance thanks to the modified break-in procedure developed for this study
Summary
Hydrogen technology is currently in the spotlight of international energy roadmaps [1]. As a key solution to limiting the increase in greenhouse gas emissions and achieving longterm greenhouse gas neutrality. In this context, fuel cells are known as clean and efficient energy converters that can be used in various sectors and application areas [2,3,4], even including special applications utilizing microbial fuel cells [5,6]. The onboard reforming of liquid fuels such as methanol or diesel carry the advantage of enabling the quicker widespread deployment of fuel cells in many mobile applications without the need to wait for a complete hydrogen infrastructure to be established around the world
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