Bipolar plate comparative costs

Properties and Estimated Cost of Nb-Clad SS430 Plates and Ni-Clad SS430 Plates with Boronized Layer Made by U.S. Pacific Northwest National Lab to Compare with U.S. DoE Bipolar Plate Technical Targets... 

Bipolar plates in PEMFCs were conventionally made of graphite with excellent corrosion resistance, chemical stability, and high thermal conductivity. However, graphite has a high cost, poor mechanical properties, and very little formability due to its microstructural nature. This limits its further applications as plate material and forces a search for alternative solutions. Nevertheless, the performance, durabilify, and cosf of fhe graphite plate (e.g., POCO graphite and graphite plates) have been taken as benchmark references to compare with those of alternative materials. 

The individual components used in an AFC are not necessarily expensive compared to those of other fuel cell t3q>es under development. Use of Ft catalysts can be avoided, while the bipolar plates collecting the electron flows typically have to be made of fairly expensive black carbon to avoid corrosion. The peripherals needed for water management and electrolyte draining add to the cost, but do not necessarily lead to drawbacks such as long start-up... 

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... 

The analysis of carbon materials used as catalyst support, gas diffusion layer, and current collector and bipolar plates is performed in Chap. 7. A number of carbon materials including carbon blacks, nanotubes, nanofibers, and structured porous carbon materials are analyzed and compared as catalyst support in direct methanol fuel cells. Commercial and non-commercial gas diffusion layers are described along with the role of the mesoporous layer on the fuel cell performance. Finally, synthetic graphite and carbon composites used as current collector and bipolar plates are discussed, focusing on their mechanical and electrical properties and production costs. 

Polymers are nsed in fnel cells. Those of particular interest are the polymer electrolyte membrane (PEM) and the phosphoric acid fuel cell (PAFC) designs. The latter design contains the liquid phosphoric acid in a Teflon bonded silicon carbide matrix. In March 2005 Ticona reported that it had bnilt the first fnel cell prototype made solely with engineering thermoplastics. They claimed that this approach rednced the cost of the fuel by at least 50% when compared with fuel cells fabricated from other materials. The 17-cell unit contains injection moulded bipolar plates of Vectra liquid crystal polymer and end plates of Fortron polyphenylene sulfide (PPS). These two materials remain dimensionally stable at temperatures up to 200 "C. The Vectra LCP bipolar plates contain 85% powdered carbon and are made in a cycle time of 30 seconds. 

Figures 7 and 8 illustrate the results of a coating benchmark, which shows clear differences in performance and durability, which depend on the coating technique and composition. With different coatings the conductivity and durability of the metallic bipolar plate exceed the properties of a composite plate with comparable flow field. Diverse low-cost coatings (RNZ 05-06, RNZ 05-12, RNZ 05-13, and RNZ 05-16), which differ mainly in their canposition, highlight the necessity to control the chemistry and electrochemistry of the complete system of plate and coating. It was shown that with optimized coating composition (RNZ 05-16) it is possible to approximate the performance and durability of the gold-coated reference plate.

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