duke University researchers have developed a power-generating membrane-based fuel cell that can operate in humid conditions, resolving an old technological problem. Commonly used in satellites, submarines or remote weather stations, fuel cells convert chemical energy into electricity. However, membrane-based fuel cells lose efficiency as temperature rises and humidity falls.
A membrane fuel cell transforms chemical energy liberated during the electrochemical reaction of hydrogen and oxygen into electrical energy. The membrane that separates two parts of the cell and facilitates the electrochemical reaction is a key factor in the cell's efficiency. The membrane used in most fuel cells is a polymer called nafion. It has the following problems:
Conductivity falls off quickly with decreasing humidity
Upper limit on operating temperature is 90C
The Duke University scientists have taken care of these problems by replacing nafion with a new ceramic membrane based on tiny iron particles. Their findings were published online on February 21, 2008, in the Journal of Membrane Science.
"The ceramic membrane," the researchers note, is a good candidate for electrolyte materials because it has thermal, chemical and mechanical stability. "The new membrane works efficiently at low humidity and should also be able to function at much higher temperatures--in the range of 150-300C," Mark Wiesner, the lead author of the paper who is with the Duke University's Pratt School of Engineering, told Down To Earth.
Organic binders such as polyvinyl alcohol, acrylic polymer, and methyl cellulose were added to the ceramic material to improve its strength and flexibility.
The researchers have not yet tested the membrane at higher temperatures but they are hopeful of its endurance because ceramic is known to tolerate high temperatures. "We anticipate that the tests will take place sometime this year. It is too early to arrive at exact costs, but based on the materials used and the procedures, we expect costs to be substantially lower. Membranes make up as much as 40 per cent of the overall cost of fuel cells," he adds.
Fuel cells have no moving parts, do not require combustion and can run unattended for long periods. "So the nearest application of the new cells will be those involving stationary applications," says Wiesner. "Once scale of their use is worked out they can be made to produce as much voltage as required," Wiesner adds.
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