Fuel cells mentioned in Table 1 are based on DMFC technology. They are compact between 100 and 200 cc and produce power between 0.3 and 9 W. The fuel cell for the cellular phone developed by Toshiba is a hybrid type, which is combined at the back of the handset with lithium ion battery. It can increase the battery run time 2.5 times longer with a single refill. The fuel cell for the cellular phone developed by Hitachi is also a hybrid type but it is more compact. One feature is that whenever its methanol fuel becomes low, it can be easily refilled from a compact cartridge[9]. The fuel cell developed by Fujitsu enables eight hours of continuous talk and improved the capacity by increasing the methanol concentration from 30% to over 99% and developing a method of recycling the generated water [10]. Samsung demonstrated the world’s smallest fuel cell mobile device charger. It produces 2W is 5mm thick and weight 5.3 ounces. It includes user-replaceable methanol cartridges. It is designed to recharge the battery system in a PDA, cell phone or digital camera [11].

Proposed design of micro fuel cell

Stack design is being suggested to be with five cells that have an electrode area around . It has the internal manifolds for supply of air and fuel. Its dimensions are 50×75 ×15 mm, this dimensions are common PDA phone sizes. Each cell of this DMFC stack has an active area around , such area is reasonable for current cell size. Ballard Power Systems Inc. recommends Nafion based MEA with GDS22100 on the anode and P75T on the cathode. GDS22100 prevents methanol crossover by controlling the methanol permeation rate. Figure 3 shows I-V curves for the mentioned idea [12].

Figure 3. Voltage versus current density for Ballard’s MEA.

Graphite could be used as bipolar plates with two flow paths.

It could be easily estimated that proposed fuel cell stack will give about 3W power, this power is enough to charge PDA phone battery.

Such fuel cell could be used like charger or even like component of mentioned hybrid power source for mobile devices, such system can provide longer life-time than common Lithium battery, but the worse things of such system are increasing sizes and mass of PDA, so it is still necessary to find some better materials and technologies for DMFC.

Of course is should be noted that such “design” is just proposal and in order to calculate output power and other important features experimental work must be provided, otherwise it is just discussion about theoretical possibility.

References

1. M.S. Wilson and S. Gottesfeld, High Performance Catalyzed Membranes of Ultra-low Pt Loadings for Polymer Electrolyte Fuel Cells, Electrochem. Soc., 139, L28 (1992).

2. D.H. Jung, S.Y. Cho, D.H. Peck, D.R. Shin, and J.S. Kim, Preparation and performance of a Nafion/montmorillonite nanocomposite membrane for direct methanol fuel cell, J. Power Sources, 118, 205–211 (2003).

3. Church, Steven (January 6, 2006). "Del. firm installs fuel cell", The News Journal, p. B7.

4. C. Heitner-Wirguin, Recent advances in perfluorinated ionomer membranes: structure, properties and applications, J. Membr. Sci., 120 1–33 (1996).

5. H. Liu, C. Song, L. Zhang, J. Zhang, H. Wang, and D.P. Wilkinson, A review of anode catalysis in the direct methanol fuel cell, J. Power Sources, 155, 95–110 (2006).

6. A.A. Kulikovsky, Voltage loss in bipolar plates in a fuel cell stack, J. Power Sources, 160, 431–435 (2006).

7. W. Vielstich, A. Lamm, and H.A. Gasteiger, Handbook of Fuel Cell, (Wiley, Chichester, England, 2003), pp. 306–7.

8. M. Hogarth, P. Christensen, A. Hamnett, and A. Shukla, the design and construction of high-performance direct methanol fuel cells. 1. Liquid-feed systems, J. Power Sources, 69, 113–124 (1997).

9. (September 28, 2005), http://www.embeddedstar.com, KDDI, Toshiba, Hitachi Showcase Mobile Phone Fuel Cells at CEATEC Japan.

10. (July 6, 2005) http://www.nttdocomo.com, NTT DoCoMo Enhances Prototype Micro Fuel Cell for FOMA Handsets.

11. (December 6th, 2006) http://www.techshout.com, Smallest Fuel Cell Mobile Charger developed by Samsung and SAIT Team.

12. http://www.ballard.com/Carbon_Fiber/Gas_Diffusion_Layer_Products/Specification_Sheets.htm, Paper-based Diffusion Layer for Direct Methanol Fuel Cells.