Bipolar plate transportation applications

There has been an accelerated interest in polymer electrolyte fuel cells within the last few years, which has led to improvements in both cost and performance. Development has reached the point where motive power applications appear achievable at an acceptable cost for commercial markets. Noticeable accomplishments in the technology, which have been published, have been made at Ballard Power Systems. PEFC operation at ambient pressure has been validated for over 25,000 hours with a six-cell stack without forced air flow, humidification, or active cooling (17). Complete fuel cell systems have been demonstrated for a number of transportation applications including public transit buses and passenger automobiles. Recent development has focused on cost reduction and high volume manufacture for the catalyst, membranes, and bipolar plates. 

Although it is difficult to determine the quantitative requirements of plate and plate materials appropriately for various fuel cells and different applications in a development phase, such a target would be helpful to direct the development effort and make necessary trade-offs. The cascaded performance requirement targets in 2010 and 2015 for bipolar plates of fuel cells in transportation applications were set by the U.S. DoE (Department of Energy) according to functions of the plate mentioned before and overall requirements of performance, reliability, manufacturability, and cost of a stack, as shown in Table 5.1 [7]. The technical target in the DoE s multiyear research, development, and demonstration plan has been popularly and worldwide... 

Stack Components In collaboration with partners, research and develop technologies to overcome the most critical technical hurdles for polymer electrolyte fuel cell stack components for both stationary and transportation applications. Critical technical hurdles include cost, durability, efficiency, and overall performance of components such as the proton exchange membranes, oxygen reduction electrodes, advanced catalysts, bipolar plates, etc. 

Metal PEMFC bipolar plates for transportation applications (Antunes, 2010). 

As can be seen from the illustrations (b) and (d) in Table 6.1 many targets like corrosion resistance electrical conductivity respectively resistivity and flexural strength are easily reached by current composite bipolar plates. Consequently, these requirements are not addressed in composite bipolar plate development (DOE, 2006). However, current composite bipolar plates are too heavy compared to the DOE targets for transportation applications. Therefore, composite bipolar plates in most instances are developed for stationary applications where there is a fewer issue of mass reduction but a target of 40,000 h of lifetime (DOE, 2009) going with composite bipolar plates being insusceptible for corrosion. 

Hence, metallic bipolar plates, promising a signiflcant mass and volume reduction, are preferable for portable and transportation applications where a target of 5000 operation hours of lifetime (DOE, 2009) is in agreement with the corrosion susceptibility of metals and stainless steel. 

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