Micro-Fabricated Thin-Film Fuel Cells for Portable Power Requirements
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Micro-Fabricated Thin-Film Fuel Cells for Portable Power Requirements Alan F. Jankowski1, Jeffrey P. Hayes2, R. Tim Graff3, and Jeffrey D. Morse3 Lawrence Livermore National Laboratory 1 Chemistry & Materials Science, 2Mechanical Engineering, and 3Electrical Engineering Livermore, CA 94551-9900, U.S.A. ABSTRACT Fuel cells have gained renewed interest for applications in portable power since the energy is stored in a separate reservoir of fuel rather than as an integral part of the power source, as is the case with batteries. While miniaturized fuel cells have been demonstrated for the low power regime (1-20 Watts), numerous issues still must be resolved prior to deployment for applications as a replacement for batteries. As traditional fuel cell designs are scaled down in both power output and physical footprint, several issues impact the operation, efficiency, and overall performance of the fuel cell system. These issues include fuel storage, fuel delivery, system startup, peak power requirements, cell stacking, and thermal management. The combination of thin-film deposition and micro-machining materials offers potential advantages with respect to stack size and weight, flow field and manifold structures, fuel storage, and thermal management. The micro-fabrication technologies that enable material and fuel flexibility through a modular fuel cell platform will be described along with experimental results from both solid oxide and proton exchange membrane, thin-film fuel cells. INTRODUCTION The portable power source problem remains a critical issue for many consumer products as well as military objectives. While rechargeable batteries have become a hindrance in the use of consumer portable electronics, present technologies are simply inadequate for the advanced military applications of remote reconnaissance and telemetry. Therefore, new power sources are required with performance criteria specific to the direct application. A lighter-weight and longer-lasting power source provides new functionality to applications that directly benefit the end user. Miniature fuel cells have recently received renewed interest for applications in portable power generation. Energy is stored as a fuel rather than as an integrated component of the system. Thus, fuel cells can exhibit significantly higher energy densities than batteries depending upon the type of fuel being utilized. While this has been demonstrated for power portable applications in the range of 50-500W, effective scaling of fuel cell systems has not been commercially demonstrated for power applications in the range of 1-20 W. Potential applications in this portable power range include consumer electronics as cell phones, laptop computers, video camcorders, and radios. New applications in portable power span the range of power consumption, from micro-power for long duration sensors and remote communication devices, to macro-power in the form of lighter weight sources for field use. A miniature fuel-cell power source can be realized through an approach that combin
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