UK research company Qinetiq is pushing on with its fuel cell/battery hybrid work in the hope that the technology will become a common source of electrical power for aerospace applications.

The principal advantage of fuel cells over traditional batteries is their higher power density per unit weight and their longevity.

Although Qinetiq is initially targeting fuel cell power packs for use with portable commercial and military systems, David Howells, the company's business development manager aerospace programmes, sees applications for the technology in commercial aircraft.

"One area we're looking at is as an auxiliary power unit [APU] replacement," he says, "but that would be some years away." The technology could provide engineers with more flexibility in selecting the location of the APU on aircraft.

Qinetiq's fuel cell technology hinges on its proton-exchange membrane fuel cell (PEMFC), a hybrid fuel cell and battery system. The cell generates electrical power by oxidising hydrogen fuel at the anode. The oxygen is obtained from the ambient air consumed at the cathode, and the only by-products are water and heat.

Gary Mepsted, principal scientist at Qinetiq's centre for environmental technology, says the useful on-load potential of a single cell is about 0.7V. "By stacking cells in a pressurised system, we can achieve power densities of 1kW/kg," he says.

The fuel cell/battery hybrid arrangement enables on-demand power generation, and Qinetiq is displaying a 25W, 12V-output demonstrator device.

Source: Flight International