DMFCs for Portable Applications

HFC R D work across the spectrum of fuel cell types and auxiliary components. Focus on PEM and large-scale MCFC and SOFC, and on micro DMFCs for portable applications. 

The theoretical power density of a DMFC at 0.5 V is about 1600 Wh per kg of methanol fuel, but in practice, small DMFCs for portable applications have achieved much less. If small DMFCs are designed like conventional PEM cells, including a membrane-electrode assembly (MEA), two gas diffusion layers, fuel and air channels with forced flows and current collectors, they may achieve power densities of about 0.015-0.050 W cm at temperatures in the range of 23-60°C (Lu et al., 2004), consistent with the value found at 85°C in Fig. 3.53. 

Blum, A. Duvdevani, T. Philosoph, M. Rudoy, N. Peled, E. Water-neutral micro direct-methanol fuel cell (DMFC) for portable applications. J. Power Sources 2003,117, 22-25. 

Goto, Y (2005) Toshiba DMFC for Portable Applications, Presented at the 7th Annual SMALL FUEL CELLS (sm) 2005—Small Fuel Cells for Portable Applications, Washington, DC., April 27-29, 2005. 

In the United States, the Department of Defense (DOD) and the Department of Energy (DOE) promoted in 1992 the Defense Advanced Research Project Agency (DARPA) program to develop a DMFC for portable and mobile applications. Several institutions are involved (IFC, JPL, LANE, Giner, Inc.) and small stacks (up to 10 elementary cells) were built by IFC and JPL. The performances are quite encouraging, with power densities of 250 mW/cm at 0.5 V. More details are given in Section V.2. 

Coutanceau C, Koffi RK, Leger JM, Marestin C, Mercier R, Nayoze C, Capron P. 2006. Development of materials for mini DMFC working at room temperature for portable applications. J Power Sources 160 334. 

In addition to these smaller applications, fuel cells can be used in portable generators, such as those used to provide electricity for portable equipment. Thousands of portable fuel cell systems have been developed and operated worldwide, ranging from 1 watt to 1.5 kilowatts in power. The two primary technologies for portable applications are polymer electrolyte membrane (PEM) and direct methanol fuel cell (DMFC) designs. 

As will be reported, as result of continuous efforts to optimize cell components and cell structure in developing DMFCs for portable power applications, we were able to demonstrate 30-cell DMFC stacks operated at 60 °C and fed with ambient air at 2-3 times faradaic stoichiometry, generating a power density of 320 W (active stack volume) during at least the initial week of testing in our laboratory. 

Direct methanol fuel cell technology is relatively new compared to that of fuel cells powered by pure hydrogen, and research and development are roughly 34 years behind that of other fuel cell types. Nonetheless, the DMFC appears to be the most promising as a battery replacement for portable applications such cellular phones and laptop computers, and a number of manufacturers are already introducing commercial versions of these applications. 

Direct methanol fuel cells (DMFCs) are potentially compact, high efficiency power sources for portable applications. One of the major problems of DMFCs is methanol crossover, meaning that methanol molecules can permeate through the Nafion membrane... 

Kamarudin SK, Achmad F, Daud WRW (2009) Overview on the application of direct methanol fuel cell (DMFC) for portable electronic devices. Int J Hydrogen Energ 34 6902-6916... 

For portable applications as a whole, the major competition is currently between PEMFCs and DMFCs. According to Jollie (2004, p. 5)... 

Eye for Fuel Cells."Fuel Cells for Portable Applications Conference Announcement." Boston September 2002 "NEC Researchers Employ Carbon Nanotubes to Design Micro DMFC for Portables." Hydrogen Fuel Cell Letter October 2001... 

Table 9.2 DMFC power sources for portable applications... 

Kwon JM, Kim YJ, Cho HJ (2011) High-efficiency active DMFC system for portable applications. IEEE Trans Power Electr 26 2201-2209... 

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