The fuel cell stack is composed of square plates made of metal, plastic or ceramic material. The plates are coated with a precious metal catalyst and covered with a polymer film similar in appearance to plastic food wrap. Two plates sandwich the film and can be stacked together in long rows. It takes a fuel cell stack about the size of an ice chest to power an automobile the size of GM's Hy-Wire concept car.
The more stacks, the greater the power output. The plates are sealed with a rubberlike gasket. The fuel cell stack must be manufactured in extremely clean conditions to prevent contamination.
The stacks are not particularly complicated. And getting them into mass production likely won't pose any challenges that manufacturing engineers can't solve, says Dennis Campbell, CEO of Ballard Power Systems of Vancouver, British Columbia. Ballard is the fuel cell supplier for about a dozen automakers, including Honda Motor Co., Mercedes-Benz, the Chrysler group, Ford Motor Co. and Mitsubishi Motors Corp.
There are several issues that must be resolved before automakers and suppliers can invest in the plants and equipment needed to mass-produce fuel cells and their parts.
"The first big challenge, and the most important, is that the design (of the fuel cell stack) itself has to become simple, easy to manufacture and repeatable," says Jim Bolch, vice president of operations at UTC Fuel Cells, the company that hand-makes the fuel cells for the space shuttle. UTC also has a growing transportation fuel cell business and has provided the fuel cell stack for two Hyundai test vehicles.
The final design of the production version of the fuel cell stack likely is nowhere near completion at any automaker or supplier.
GM, for instance, hasn't finished its fuel cell stack design. GM is trying to reduce costs by a factor of 10, from $500 per kilowatt hour of energy produced to $50 an hour, to bring it in line with today's internal combustion engine.
Ballard and UTC agree that the cost must come down to that level before fuel cell vehicles will be able to compete with today's cars. If engineers are successful in producing a fuel cell that meets the cost target, chances are that it will be different from the fuel cells that are handmade today.
GM engineers and scientists are trying to achieve the cost reduction by using different combinations of materials and by varying the amount of precious metals.
Burns says GM produces a smaller and more powerful generation of fuel cells every quarter. With design changing so often, there is little movement on the manufacturing front right now.
"Like all rational businesspeople, you don't want to overcapitalize too soon," UTC's Bolch says. If the design (of the stack) changes after capital is put in, you may run the risk of having to recapitalize with new equipment."
GM believes that selling stationary fuel cells could speed the process of getting automotive fuel cells into mass production. GM is marketing hydrogen fuel cell generators to learn about production and to test their reliability and durability. GM recently signed a deal with Dow Chemical Co. to provide 500 stationary fuel cells for electricity production for Dow factories in Texas.