Solid fuel cell works in heat

California Institute of Technology researchers have built a type of fuel cell that uses a solid acid electrolyte and either hydrogen or methanol as fuel. It could eventually be used to power cars.

Fuel cells are cleaner than combustion engines because they extract energy from a fuel chemically rather than burning it. In a fuel cell, the electrolyte acts as a conduit for electrons.

The researchers' phosphate-based electrolyte material has potential advantages over current polymer solid electrolytes, including the ability to produce electricity at temperatures over 100 degrees Celsius and less chance of fuel leakage. The researchers demonstrated the fuel cell's viability by having it produce electricity for 100 hours at a temperature of 250 degrees Celsius.

The trick to using the solid acid electrolyte is having enough water vapor pressure -- about 10 percent relative humidity at 100 degrees Celsius -- to keep the material from dehydrating. This is relatively easy to do, according to the researchers.

The challenges to making a practical fuel cell from the material include scaling up the system from a single cell that puts out just a few thousandths of a watt of power to a system that produces enough power to run a real device. A car, for instance requires about 60,000 watts.

A prototype vehicle that uses the solid acid fuel cell could be on the road in five years, according to the researchers. The work appeared in the November 20, 2003 issue of Science.