Fuel Cell Roadblocks
In
vehicular applications, there are many reasons why current prototype fuel
cells may not become popular. For example, Ballard
Power System's Nexa power module can demand an operating pressure of up
to 240 psi (standard pressure is 14.7 psi). Cells generally only work
in an environment with up to 95% humidity, so the cell may fail to function
in climates that routinely have almost 100% humidity. The upper limit
on the operating lifetime of most fuel cells is 1500 hours, which means
a whole new system would need to be purchased every 50,000 to 75,000 miles.
Because they are not yet a popular form of power generation, fuel cells are not an economically feasible form of power. The United States Department of Energy states that the most widely marketed fuel cells cost about $4,500 per kilowatt. More conventional forms of power, such as a diesel generator, costs $800 to $1,500 per kilowatt, and a natural gas turbine costs even less.
Hydrogen gas for a fuel cell must be extremely pure or the catalyst will be quickly poisoned. These catalysts are currently expensive, and therefore can not be easily replaced. (See Catalysts.) Storage of hydrogen is also not currently efficient in terms of tank space. (See Hydrogen Storage Possibilities.)
There is considerable ongoing research to overcome these potential roadblocks. By developing new catalyst materials and methods of catalyst application, researchers hope to reduce the cost of fuel cells and make the catalyst less sensitive to CO poisoning. PEM fuel cell researchers are looking for new polymer membranes to improve the performance and durability of their fuel cells. In order to operate properly, the membrane must remain humidified, which prohibits operation at higher temperatures. However, there are benefits to operating at higher temperatures such as resistance to catalyst poisoning and higher output current densities. New membrane materials under development will stay humidified at higher temperatures, making fuel cells more likely to find use in vehicles and other applications. Not only will they be less sensitive to catalyst poisoning, but also smaller fuel cell stacks will be required to get the same power output, thus lowering their cost.
Photo of Nexa power module courtesy of Ballard, Inc.