Cell stack development, direct methanol

H. Dohle, H. Schmitz, T. Bewer, J. Mergel, and D. Stolten. Development of a compact 500 W class direct methanol fuel cell stack. Journal of Power Sources 106 (2002) 313-322. 

A serious candidate for transportation application is also the direct methanol fuel cell (DMFC) which has been realized already on a laboratory scale. A catalytic burner is requited to evaporate the methanol/water mixture and to bum the exhaust gas at the anode [43]. Considering the complete energy chain, a PEFC is by 50 % more efficient than a diesel engine which consumes 4 1 per 100 km this is also valid for a natural gas driven engine [37]. Fig. 7-6 presents the processing schematics of both IMFC and DMFC. The DMFC offers a much simpler system than the PEFC. The DMFC is currently at an early development stage. It is perceived to offer improved solutions to the need for a small-scale power supply. A program for the construction of a 30 kW stack has recently started [29]. 

Simoglou A, Argyropoulos P, Martin EB, Scott K, Morris AJ, Taama WM (2001) Dynamic modeling of the voltage response of direct methanol fuel cells and stacks. Part I model development and validation. Chem Eng Sci 56 6773-6779... 

Argyropoulos P, Scott K, Taama WM (1999) One-dimensional thermal model for direct methanol fuel cell stacks. Part I. model development. J Power Sources 79 169-183... 

Cremers C, Scholz M, Seliger W, Racz A, Knechtel W, Rittmayr J, Grafwallner F, Peller H, Stimming U (2007) Developments for improved direct methanol fuel cell stacks for portable power. Fuel Cells 7 21-31... 

The preparation complexity of perfluorosulfonated membrane and the high cost have restricted PEMFC from commercialization. Many researchers are dedicated to the development of nonflnorinated PEM. The American company Dais has developed styrene/ethylene-bntylene/styrene triblock polymer [51]. This membrane is especially snitable for small power PEMFC working at room temperature. The lifetime of the membrane is up to 4000 h. Baglio did some experiments to test the performance comparison of portable direct methanol fuel cell mini-stacks between a low-cost nonfluorinated polymer electrolyte and Nafion membrane. He found that at room temperature, a single-cell nonfluorinated membrane can achieve maximum power density of about 18 mW/cm. As a comparison, the value was 31 mW/cm for Nafion 117 membrane. Despite the lower performance, the nonfluorinated membrane showed good characteristics for application in portable DMFCs especially regarded to the perspectives of significant cost reduction [52]. 

---