Bipolar plate stack cost

The costs of a PEMFC stack are composed of the costs of the membrane, electrode, bipolar plates, platinum catalysts, peripheral materials and the costs of assembly. For the fuel-cell vehicle, the costs of the electric drive (converter, electric motor, inverter, hydrogen and air pressurisation, control electronics, cooling systems, etc.) and the hydrogen storage system have to be added. Current costs of PEM fuel-cell stacks are around 2000/kW, largely dominated by the costs of the bipolar plates and... 

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... 

Section 5.2.2 include composites and metals. From a cost reduction point of view, it is estimated, according to the cost model, that the cost percentage of the plate in a stack can be reduced from -60 to 15-29% if the graphite plate were replaced by the composite plate or metal plate [15]. However, many uncertain factors are involved in the estimation. The progress and major challenges in development of bipolar plates fabricated by these candidate materials will be introduced in the following parf of this section. 

The manufacturing cost of a PEM fuel-cell stack includes the individual costs of the membrane, the electrodes, the platinum catalyst, the bipolar plates, the... 

According to the aforementioned, it is possible for the cost of the PEM fuel-cell stacks to be lower than even 70 /kWe in the near future, while a projected cost of only 40 /kWe might be possible, assuming a power density increase to 4 kW m2 and the use of cheaper electrodes and bipolar plates. 

Graphite-based composites and metal/alloy materials both have their own advantages and drawbacks. Current research interests in bipolar plate materials include both graphite composites and coated metals. No doubt progress on these materials will eventually lead to substantial reduction in the volume and cost of the fuel cell stack. 

The cost of non-active materials (gas diffusion layer, membrane, and bipolar plates) dominate stack cost at very low platinum loadings, while ohmic losses limit the benefit of increasing platinum loading beyond some point. 

In the bipolar arrangement, the bipolar plate becomes the main constmction element, of the fuel cell stack. Besides the performance of the electrochemical components, the characteristics of the bipolar plate determine the performance of the fuel cell stack with respect to specific power and volume. As the bipolar plate is also a significant cost contributor in the fuel cell stack, an optimized bipolar plate has to fulfil a series of requirements. 

The present market situation is characterized by a small number of units and hand fabrication. Figure 8.18 compares the present situation of the stack production by a research institution with the prediction of ADL by plotting the cost distribution of PE fuel cell stacks. The present cost for the manufacture of a single unit is about a factor of 10-50 more expensive than the values of the ADL analysis. As can be seen, the importance of bipolar plates is presently about equal to that of the MEA and labor-intensive tasks like assembling and quality control contribute significantly to the cost of the stack system. These are the cost drivers that can be... 

Beside the MEA the bipolar plates are the key components in a PEMFC stack in terms of their contribution to weight, volume, and costs. Bipolar plates contain a fine mesh of gas channels called the flow-field, to ensure a uniform distribution of the process gasses (hydrogen and oxygen) of fuel and air across both sides of the MEA and the removal of the reaction products. Furthermore, the bipolar plates in PEM fuel cells separate the individual cells from each other and guarantee an electrical connection between them in series. Substantial requirements for the bipolar plates are a high electrical conductivity and corrosion resistance. 

A detailed cost analysis for a polymer electrolyte membrane fuel cell power plant of 5 kW was provided in 2006 by Kamarudin et al. According to their data, the total cost of such a plant will be about 1200 of which 500 is for the actual fuel-cell stack and 700 for the auxiliary equipment (pumps, heat exchangers, etc.). The cost of the fuel-cell stack is derived from the components as 55 /kW for the membranes, 52 /kW for the platinum, 128 /kW for the electrodes, and 148 /kW for the bipolar plates. 

From energy-density and volume-production points of view, the use of metallic bipolar plates in PEMFC stacks is important for the automobile industry. Metallic bipolar plates could provide thinner and hghter choices and improved thermal and bulk electrical conductivity. The use of SSs makes PEMFCs cost-effective. Whereas 316/316L SS may not be the optimum choice for the PEMFC bipolar plate... 

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