Question:
When you speak of making fuel cells practical, exactly what kind of issues are involved?
For example with proton-exchange membrane fuel cells, you have a catalyst stuck to the anode side of an electrolyte membrane, air pockets for oxygen on the cathode side, and a separator between the cells (see figure 4). The first set of issues is how to reduce the cost of the electrolyte membrane, and how to achieve the right operating temperatures. The material for the fluorinated membranes used now costs approximately 400-800 US dollars per square meter, and we have to cut that by 1/10 or 1/20. As for the operating temperature, the current membranes can only be used at 100°C or lower. However, at temperatures below 100°C, carbon monoxide may get mixed in with the hydrogen fuel which reduces the performance of the catalyst. Another drawback of low temperatures is that while the small amount of residual heat can be used to create hot water, if we could capture enough waste heat to generate steam, we could put that steam to good use. And in the case of automobiles, we would only need a radiator of the same size of those used for gasoline engines. For such reasons, we really need a membrane that can function at high temperatures.The second issue is that of the catalyst itself. For low temperature operation we need highly active platinum, which is currently being consumed in markets at the rate of approximately 150 tons per year. Platinum is extremely expensive and rare, so we have to pare down the amount of required catalyst by 1/10 the current levels. The third issue is that of the separator. In typical configuration, 200-300 fuel cells are stacked together. The separator is placed in between each one and serves to connect them electrically. Also, the separator has grooves that allow gas to be supplied to the cell. Currently, the grooves are made by carving them out of the graphite material of which the separator is composed. But to reduce cost, manufacturers are trying to produce the next generation of separators by combining carbon materials and plastic, then using presses and injection molding techniques. But even that is very expensive. Implementation costs by the methods in a few tens to hundreds of dollars must be brought down to less than one to two dollars. These are the three major issues, but there's also the issue of drastically expanding the lifespan of proton-exchange membrane fuel cells in order to ensure the reliability of products in which they are used. For example, if you're using the cells for home appliances, the cells would need to have the same long lifespans of current home electronics (ten years). This issue of how to guarantee a ten-year lifespan is critical. In addition, fuel cells must be reliable in any operating environment, such as in metropolitan areas where the air quality may be poor. Also, for automobiles, the cells have to function under strict conditions for air temperature,start/stop, and load fluctuations.
In order to promote fuel cells other than the proton-exchange membrane types, there is a mountain of problems that we must consider including materials, cost, and lifespan.
