Lightweight fuel cell ideal for UAVs

A compact fuel cell developed by German researchers weighs only 30g yet can generate enough electricity to power a helicopter.

The device, which has emerged from work carried out by scientists at the Technical University of Berlin and the Fraunhofer Institute for Reliability and Microintegration  has a power density of 400W per kilogram, a level that has so far only been achieved in considerably larger systems weighing several hundred grams.

That makes it light enough to run a 20cm diameter unmanned helicopter designed for missions such as locating victims trapped in fallen buildings, monitoring traffic or investigating tracts of land that have been contaminated by chemical accidents.

The group made their breakthrough by replacing the metal plates normally used in fuel cell stacks with plastic spacers. They have also been able to eliminate the pump usually required to provide an adequate air supply because wind generated by the helicopter̵7;s rotor blades can be directed straight in to the air vents.

Another challenge was to devise a solution for the hydrogen supply, as a conventional pressure tank would be too heavy for the helicopter. ̶0;We have built a small reactor containing solid sodium borohydride. If we inject water, this produces hydrogen,̶1; explained team leader Dr Robert Hahn.

The researchers have already built a prototype of the lightweight fuel cell and expect the helicopter to be ready for test flights in just over a year̵7;s time.

Image: The fuel cell is not much bigger than a matchbox

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