Sep 5 2005
A single fuel cell does not produce enough energy to power a car. So fuel cells are stacked, with a bipolar plate between each cell through which electrons are conducted. The hydrogen fuel and oxygen, which are part of the fuel cell chemistry, enter the plate through channels along the face on each side of the plates. Creating the channels in the bipolar plate is a manufacturing challenge.
About 29 percent of the cost of a fuel cell stack is the bipolar plate, and machining channels into the plates is a significant factor, said Donald Baird, who is the Harry C. Wyatt Professor of Chemical Engineering at Virginia Tech. "Machining 1 millimeter by 1 millimeter (1 mm x 1 mm) channels is expensive and time consuming."
So researchers at Virginia Tech are developing compression moldable composite bipolar plates with channels included. Baird and Jianhua Huang, research scientist in chemical engineering at Virginia Tech, presented their research at the 230th American Chemical Society National Meeting, being held in Washington, D.C., Aug. 28-Sept. 1.
Using a thermoplastic composite and a wet-lay process, the researchers created a material with high electrical conductivity and good mechanical properties, that is a barrier to hydrogen and oxygen, and is easy to manufacture so that the channels can be molded in. The properties of the bipolar plates, which will be discussed at the ACS meeting, exceed the Department of Energy's minimum standards and industry requirements in terms of electrical conductivity along the plate and of strength. "Through plane conductivity needs some improvement (presently values as high as 35 S/cm are obtained)," Baird said.
The Virginia Tech researchers are continuing to work on optimizing the manufacturing scheme – how fast the channels can be created and the material can be cooled, Baird said. "We are also working on different methods of heating, such as induction versus microwaving."
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