Chemical engineers at the University of Pennsylvania have developed a prototype fuel cell that’s the first to run on diesel fuel. The work is said to bring fuel cells closer to viability, offering the promise of compact, portable power sources that are more economical than combustion engines or existing batteries.
Fuel cells are far more efficient and less polluting than other energy sources but work to develop commercial fuel cells has been hindered by the limited fuel sources on which they have been known to run.
‘There used to be a saying that you could run a fuel cell on any fuel as long as it’s hydrogen,’ said Raymond J. Gorte, professor of chemical engineering and the lead author of a Journal of the Electrochemical Society paper reporting the finding.
Gorte and colleague John M. Vohs, professor and chair of chemical engineering at Penn, shook the fuel cell world in March 2000 with the publication of a Nature paper in which they reported developing a fuel cell that could run on butane, the first fuel cell to operate on a fuel other than hydrogen.
With the development of a fuel cell that runs directly on liquid diesel the team has side stepped the thorny problem of ‘reforming’ fuels to hydrogen to run fuel cells.
‘In our earlier work, we were unable to feed liquid diesel to the fuel cell because we did not have a means for vaporising fuels that have a low vapour pressure at room temperature,’ Gorte said. ‘This paper demonstrated that we could feed these liquids to a fuel cell using a method analogous to a fuel injector in an internal combustion engine and still get stable operation of the fuel cell.’
Past research with fuel cells has focused on how best to process, or ‘reform,’ available hydrocarbon fuels such as diesel into pure hydrogen, which is an expensive and inefficient proposition.
The Penn fuel cell is said to be the first to run directly on hydrocarbons, without requiring complicated reforming into hydrogen either within the device itself or at specialised filling stations. Generating electric power through controlled electrochemical reactions rather than combustion, its only emissions are water, carbon dioxide and heat.
Smaller than a penny, the prototype fuel cell developed by Gorte, Vohs, graduate student Hyuk Kim and postdoctoral researcher Seungdoo Park operates in a furnace set at 700 degrees Celsius. A commercial, self-contained fuel cell would ideally generate that heat itself using the fuel placed in it.
Although unlikely to replace household batteries for small appliances and portable electronics, researchers have suggested that fuel cells might be appropriate for powering cars and laptop computers.
‘We are excited by the progress that Professor Gorte and his colleagues are making in the area of direct oxidation of hydrocarbon fuels using solid oxide fuel cells,’ said David Bauer, team leader for the Solid Oxide Fuel Cell project at the Ford Research Laboratory. ‘The ability to utilise conventional fuels with little or no reforming is particularly important in transportation applications where fuel storage and system packaging are such critical issues.’
Fuel cells could also make possible electric generators that operate on propane or butane.
Gorte’s team is interested in developing a relatively small, five-kilowatt fuel cell. Such a unit, placed in a home’s basement, could be used to generate electricity from natural gas, using the excess energy to heat the home or its hot water.