Liquid Tin Anode Solid Oxide Fuel Cell Direct JP-8 Applications

Abstract

The Liquid Tin Anode Solid Oxide Fuel Cell (LTA-SOFC) is a unique technology that allows the direct oxidation of hydrocarbon and carbonaceous fuels. This enables a more efficient and compact system for a wide range of applications. The LTA-SOFC uses many conventional SOFC materials but allows a much greater range of fuels to be utilized on the anode. The Liquid Tin Anode directly converts JP-8 or other hydrocarbons to electrical power without reformers or other fuel processing. In addition, the anode stores energy, allowing the cell to deliver power even when fuel flow has been interrupted. As a result, the LTA-SOFC system is simpler and more efficient than competing generation technologies. This paper describes the basic LTA-SOFC cell architecture and the concept of direct carbon fuel cells. Material and component design challenges associated with improving anode performance are discussed. Test data shows the impact of anode improvements in achieving higher power density. Cell/stack test results are presented using JP-8, feedstock. Potential applications for military and commercial portable power are discussed. Operation on JP-8: Our Gen 3 cell has demonstrated fuel efficiency of between 20% and 40% (LHV) on JP-8. A single cell was operated continuously on untreated JP-8 with 1341 ppm sulfur for 200 hours. Cell performance benchmarked throughout the 200 hour test did not show any performance degradation. Stack performance is very similar to single cell. Cell Design Improvements: Under a DARPA/Army contract the LTA-SOFC has been refined for a battery charger application in the range of 500 Watts (Gen 3.1). This third generation design is tubular, cathode supported with a very thin external tin anode. This design allows the introduction of gaseous, liquid and solid fuels directly into the anode chamber with no preprocessing or fuel reforming. Carbon formation is acceptable, since solid carbon is oxidized as a fuel even without direct contact to the tin anode. The Gen 3 cell has achieved a power density of over 100 mW/cm on JP-8 and shown no degradation after 5 thermal cycles. System Performance: Early adoption is expected in military or emergency power markets in the 20 Watts to 10 kW range using JP-8 or diesel. Based on recent test data, we have established a cell performance target of 200 mw/cm power density operating directly on JP-8. System analysis based on this performance indicates that the dry weight of a complete 500 Watt system will be about 10 kg. For extended missions, the total system energy density will approach 3000 wh/kg which exceeds the performance of any other battery or small power generator. In portable power applications, the LTA-SOFC system provides significant weight and volume advantages while operating on readily available logistics fuel. 5th International Energy Conversion Engineering Conference and Exhibit (IECEC) 25 27 June 2007, St. Louis, Missouri AIAA 2007-4766 Copyright © 2007 by CellTech Power LLC. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Corresponding author, Jeff Bentley, CellTech Power, LLC, 131 Flanders Road, Westborough, MA 01581, 508-898-2223 ext 34, jbenteyl@celltechpower.com