PEFC Applications

A fuel processor for PEFC application contains sulfur removal, an ATR-enhanced UOB reformer, advanced shift reactors, a steam generation system, a product gas cooler, a PROX system, a gas compressor, an air compressor, an anode-off gas oxidizer, and a control system. Goal efficiency (LHV H2 consumed by fuel cell/LHV fuel consumed by fuel processor) is 69 to 72%. H2 concentration is presently >50% (dry). 

Removal of CO from Reformate for PEFC Application," S. Lee, R. Kumar, M. Krumpelt, ANL, Pg. 578, Fuel Cell Seminar Abstracts, Courtesy Associates, Inc., November 1998. 

Savadogo, O. 2004. Emerging membranes for electrochemical systems—Part 11. High-temperature composite membranes for polymer electrolyte fuel cell (PEFC) applications. Journal of Power Sources 127 135-161. 

It was found for PEFC applications that the hydration of the electrolyte membrane is critical for good performance. If the membrane is too dry high resistivity results, whereas, if the water flux is too great it can lead to cathode flooding. For proton transport to occur in Nafion -based membranes,... 

Having passed through the reformer, the sulfur concentration is lower than 1 ppmv H2 S due to chemical conversion and dilution with air and steam. A further removal process for H2S is required depending on the fuel ceU type. The sulfur tolerance of different fuel ceU types cannot be clearly defined and further studies are necessary with regard to long-term stability. A threshold of 0.1 ppmw H2S for PEFC application is the most chaUenging task. 

Despite reeent progress in developing multiscale modeling approaches [117], enormous challenges remain in bridging between atomistic simulations of realistic structures and continuum models that describe the operation of functional materials for PEFC applications. While full multiscale methods will not be available in the near future, meso-scale simulation techniques can close the gap between atomistic simulations and macroscopic properties of the system. Such simulations provide vital insight into self-organization phenomena and adhesion properties that have to be considered in the fabrication and operation of CL materials for PEFCs [118]. 

Gatto I, Sacca A, Carbone A, Pedicini R, Urban F, Passalacqua E. CO-tolerant electrodes developed with phosphomolybdic acid for polymer electrolyte fuel cell (PEFCs) application. J Power Sources 2007 171 540-5. 

Hu, Z., Yin, Y., Chen, S., Yamada, O., Tanaka, K., Kita, H., Okamoto, K.I. (2006) Synthesis and properties of novel sulfonated (co)polyimides bearing sulfonated aromatic pendant groups for PEFC applications. Journal of Polymer Scierwe Part A Polymer... 

Example 4.12 Calculating Crossover Losses In ref. [9], the authors noted a hydrogen crossover loss of 3.3 mA/cm for their automotive H2 PEFC applications. Calculate the mass crossover rate of hydrogen through the membrane. Also, calculate and plot the cathode activation overpotential loss at open circuit and 1 A/cm as a function of cathodic exchange current density. Assume the cathodic charge transfer coefficient at the cathode is 1.5 at a temperature of 353 K, and the fuel cell has a 50 cm geometric area. 

Ethylene glycol (EG, C2H6O2) is ubiquitously used in the automotive industry as an engine coolant, and hence a distribution infrastructure already exists. Also, EG has a crossover current density roughly half that of methanol [69]. However, PEFC performance with EG is still relatively low, with a fuel cell specific energy density about 20-40% less than that of the same fuel cell utilizing methanol. Additionally, EG has been shown to rapidly degrade PEFC elecfiolyte material, which obviously limits its potential PEFC applications. 

Fuel Flexibility The MCFC can internally reform a wide variety of fuel sources and use carbon monoxide as a fuel, a major poison in PEFC applications. This alleviates the need for a hydrogen infrastructure with this system. 

Inexpensive Catalysts and Metal Materials High-temperature operation eliminates the need for expensive noble metal catalysts found in PAFC and PEFC applications. Non-noble metal catalysts are used, typically nickel-chromium or... 

Sauk, J., Byun, J., and Kim, H. (2005). Composite Nafion/polyphenylene oxide (PPO) membranes with phosphomolybdic acid (PMA) for direct methanol fuel cells. J. Power Sources 143, 136. Savadogo, O. (2004). Emerging membranes for electrochemical systems. Part II. High temperature composite membranes for polymer electrolyte fuel cell (PEFC) applications. J. Power Sources 127,135. Schuster, M., Meyer, W. H., Wegner, G., Herz, H. G., Ise, M., Schuster, M., Kreuer, K. D., and Maier, J. (2001). Proton mobihty in ohgomer-bound proton solvents Imidazole immobilization via flexible spacers. Solid State Ionics 145, 85. 

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