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Research Papers

Development of Direct Methanol Fuel Cell Systems for Material Handling Applications

[+] Author and Article Information
J. Mergel1

 Institute of Energy and Climate Research – Fuel Cells (IEK-3), Forschungszentrum Jülich GmbH, 52425 Jülich, Germanyj.mergel@fz-juelich.de

H. Janßen, M. Müller, J. Wilhelm, D. Stolten

 Institute of Energy and Climate Research – Fuel Cells (IEK-3), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany

1

Corresponding author.

J. Fuel Cell Sci. Technol 9(3), 031011 (Apr 26, 2012) (10 pages) doi:10.1115/1.4006490 History: Received January 12, 2012; Revised March 28, 2012; Published April 26, 2012; Online April 26, 2012

Direct methanol fuel cells (DMFCs) are attractive for various applications, above all, however, as replacements for batteries or accumulators. They may be used in different power classes. A market analysis indicated that the use of a DMFC energy system in the kW class had the best chance of commercial realization if applied in forklift trucks for material handling in large distribution centers or warehouses. An advantage of such energy systems is that there is no need for the relatively time-consuming recharging of the lead-acid batteries, nor is it necessary to have spare batteries available for multishift operation. This calls for DMFC energy systems that are capable of replacing the existing Pb accumulators in terms of space requirements and energy. However, this requires considerable improvements to be made in terms of power and stability over time of DMFC systems and, in comparison to their present status, an increase of overall efficiency. Recent cost analyses for the overall system; for example, show that for the DMFC stack, a durability of at least 5000 h must be achieved with an overall efficiency for the DMFC system of at least 30%, with the constraint that the system can be operated in a water-autonomous manner up to an ambient temperature of 35 °C. As part of a joint R&D project with industrial partners, two systems were constructed and each subjected to long-term testing for 3000 and more than 8000 h, respectively, with realistic load profiles from driving cycles. In this test, the stack from the first system, DMFC V 3.3–1, displayed an aging rate of approximately 52 μV h−1 at a current density of 100 mA cm−2 . This corresponds to a performance degradation of 25% over a period of 3,000 h. The DMFC V 3.3–2 system, a modified and optimized version of the first system, also underwent long-term testing. In this case, the aging rate of the stack was only approximately 9 μV h−1 at a current density of 100 mA cm−2 . The system has thus been operated to date for more than 8000 h under realistic load profiles.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Energy content of various energy carriers with and without considering the required tank

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Figure 2

Operating range of forklift trucks with various energy carriers in comparison to a lead-acid battery (internal combustion engine (ICE))

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Figure 3

DMFC fuel cell system in electric vehicles: (a) JuMOVe from 2005, (b) JuMOVe 2 from 2006

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Figure 4

(a) Horizontal order pickers and (b) forklifts in typical warehouse applications

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Figure 5

Technology comparison: lead-acid battery versus DMFC energy system (Total costs*: includes the costs of the energy system, the depreciation of the charging stations/filling stations, personnel costs for changing battery systems/refueling; electricity, methanol, maintenance and storage space costs, Operating range**: cost-optimized design)

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Figure 6

Technology comparison: lead-acid battery versus DMFC energy system at an MEA power density of 100 mW cm−2 and a stack lifetime of 10,000 h

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Figure 7

Typical driving profile for order picker application

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Figure 8

Long-term measurement of battery current, voltage and power for a typical order picker application

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Figure 9

Characteristic order picking operation

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Figure 10

Load profiles for systems analysis and long-term tests: (a) realistic driving cycle and (b) approximated driving cycle

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Figure 11

DMFC system’s hybridization concept

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Figure 12

Basic process technology and electric setup of the DMFC hybrid system

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Figure 13

DMFC Stack: (a) Photo of a 90-cell stack with an active area of 315 cm2 per cell and (b) the current/voltage characteristic at 70 °C and 1 M methanol solution

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Figure 14

System packaging DMFC V3.3 system and DMFC system in the battery tray

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Figure 15

Representation of stack aging for DMFC V3.3-1 as voltage loss at constant current density after filtering the measured data; TStack  = 48 to 61 °C, cMeOH  = 0.45 to 0.95 M, cathodic volumetric flow = 16.4 to 26.2 ml cm−2 min−1

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Figure 16

Representation of stack aging for DMFC V3.3-2 as voltage loss at constant current density after filtering the measured data; TStack  = 61 to 73 °C, cMeOH  = 0.4 to 0.8 M, cathodic volumetric flow = 5 to 13 ml cm−2 min−1

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