Cost-Effective Liquid-Fueled PEN Fuel Cell Systems for Stand-Alone Power Applications

摘要

Successful development of cost-effective, polymer-electrolyte-membrane fuel cell (PEMFC) systems for sub 10-kWe standalone applications, which run on liquid hydrocarbon fuels, largely depends on integrating fuel processing and any necessary H2 purification with reliable fuel cell operation. Current low-temperature, Nafion-based fuel cell (LT-PEMFC) stacks require significant reformate purification with preferential CO oxidation reactors, Pd-alloy membranes, or pressure-swing absorption systems to ensure that the anode fuel feeds have adequately low CO concentrations to permit stable stack operation. These H2 separation-techniques can be costly in terms of system efficiency and operability/complexity. To reduce the need for H2 purification, promising developments for high-temperature PEM fuel cells (HT-PEMFCs) using doped electrolyte membranes other than Nation operate at temperatures between 160 and 180 °C, which significantly improves stack tolerance of CO such that typical impure H2-rich streams from hydrocarbon fuel processors with good water-gas-shift reactors can be directly fed to the stack. However, to date, HT-PEMFC stacks require substantially higher electrocatalyst loadings (> 3X that of LT-PEMFCs) and operate at substantially lower efficiencies and power densities, which currently limit their cost effectiveness for standalone power applications. Cost and performance challenges associated with HT-PEMFCs may be addressed through long-term investment, but it remains to be seen whether such systems will be more promising than LT-PEMFCs operating in conjunction will optimized fuel processing and adequate H2 purification or CO tolerance for cost-effective stand-alone power applications.