Low-Cost Pemfc Development at Siemens - Material Aspects

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ABSTRACT A state of the art review is given on conceivable concepts of cost reduction for PEM fuel cell systems with specific respect to mobile applications. Achieved results at Siemens are described and will be taken as a basis to assess how close this technology is to the market. INTRODUCTION Proton Exchange Membran Fuel Cells (PEMFC) in combination with an electric drivetrain are being more and more discussed as a potential solution for a clean and energy-efficient transportation. Exceeding academic visions, car manufacturers meanwhile took up this idea: they already demonstrated the technical feasibility of a corresponding propulsion concept by fuel cell driven prototypes. Main obstacle for a fast market penetration are the system costs which currently exceed 104 $/kW. In order to become the follow-up generation of the present day drive systems, fuel

cells will have to face a strong competition from the established combustion engines (ICE). So, in order to get any acceptance among the endbuyer, the highest challenge in the future will lie in the realisation of costs which will be comparable to ICEs. Results on the described issues will be shown and discussed. EXPERIMENT All electrochemical fuel cell experiments were conducted in small 3 cm2 single cells. The cell frames are made of an Ni-based alloy. In order to keep contact resistivities as low as possible, they are gold-plated. The humidification section is integrated in the cell. A pressure sensor is applied to control the mechanical compression of the cell. A serpentine structure is used for a coarse gas distribution. The test device is shown in fig. 1. A conventional electronic load is used to operate the cell. U-I characteristics are recorded in a galvanostatic mode, also long term tests were performed with constant load. In all experiments the reactants are humidified at cell temperature. The ex-situ corrosion experiments were conducted in a PMMA-cell comprising a conventional 3-electrode arrangement (fig.2). These experiments were performed at room temperature and under ambient air atmosphere. The material samples were cut into discs of 25 mm diameter. The surface was polished with a diamond paste (1 gtm) to achieve reproducible surface roughness.

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Mat. Res. Soc. Symp. Proc. Vol. 575 ©2000 Materials Research Society

Fig. 1: 3 cm 2 fuel cell for material tests

-Rference Electrode I

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I I(Glassy

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filled with electrolyte

~ MA..MA) (Fe-basdalloy)

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