(390b) Design and Integration of Portable Sofc Generators

Although the majority of development on solid oxide fuel cells to date has been directed towards multi-kilowatt systems for stationary applications, recent advances in high power density stacks, compact reformers and system architectures have made it possible to build portable SOFC generators with power ratings under 500 W.  Portable SOFC generators in this class could be competitive with PEM and direct methanol systems, particularly in light of their ability to operate with hydrocarbon fuels.  Capable of using fuels ranging from methane and propane through gasoline and kerosene, these generators can operate over wide environmental temperature ranges, can be more efficient than internal combustion engines, and can achieve high power and energy densities. 

Over the past six years, Mesoscopic Devices, LLC and its partners have been developing the core technology required to build compact, efficient portable SOFC generators in sizes under 500 W.  In this paper, we report on the design and testing of the MesoGen?-75 and MesoGen-250 portable SOFC generators having output powers of 75 and 250 W, respectively.  Intended for military and industrial uses, these prototypes (shown in Figure 1) demonstrate the practicality of solid oxide fuel cell generators under 500 W.  Applications include field battery charging, remote power, and low level auxiliary power. 

Figure 1.  The 250 W MesoGen?-250 (left) and the 75 W MesoGen-75 (right) SOFC generators.

The MesoGen-75 is a man-portable generator approximately 130x180x250 mm, with a dry mass of 3 kg and a fuel consumption of ~0.55 kg/day.  Two versions of the system have been developed, one operating on propane, and one on low-sulfur kerosene. Future models will use kerosene (jet fuel or military JP-8) processed through a separate liquid-phase desulfurizer also under development at Mesoscopic Devices.  The generator includes an internal hybrid battery, and can provide peak power of up to 150 W.  Both 12 V DC and 24
VDC output are available from the same system.  The MesoGen-250 is 178x203x356 mm, with a dry mass of 6.3 kg, and a projected fuel consumption of ~1.8 kg/day.  This system is intended to run on liquid fuels and perform as a battery charger for multi-day field operations. 

These portable SOFC generators are made possible by advances in three key areas: high-power-density lightweight stacks, compact fuel processing equipment, and optimized balance-of-plant components.  Tying these elements together into a practical system requires particular attention to component integration, thermal management, and balancing component level performance tradeoffs to optimize overall system level performance.  Furthermore, design optimization must be constrained by practical considerations including reliability and manufacturing costs.  This paper will describe many of the key system components and their integration in portable SOFC generators including fuel processing equipment, fuel and air metering components and methods, thermal management, and overall system integration and control strategies.