Unmanned Systems Technology 014 | Quantum Tron | Radio links and telemetry | Unmanned Aerial Vehicles | Protonex fuel cell | Ancillary systems | AUVSI 2017 Show report

51 providing a suitable hydrogen supply in the field. Around 2004, Protonex switched to developing fuel cells for UAV propulsion, working in conjunction with the research laboratories of the US Navy and US Air Force. The main issue was to find an increase in power density. “Existing fuel cells weren’t designed around aircraft applications,” explains Paul Osenar, president of Protonex. “Fortunately for us though, both research laboratories were willing to look forward and ask, ‘What would it take to get there?’ “We use a PEM [proton exchange membrane] cell – there are alternatives but it is the most mature technology with the highest power density. We won a series of contracts from the two laboratories that allowed us to explore how to push the PEM technology, not from a core materials science point of view but more in terms of packaging and integration including thermal management, all to get the power density of the stack higher, and from there to get the overall system power density up.” Protonex’s development work led to a 1 kg UAV FC producing 550 W (0.73 bhp). That 1 kg weight does not include the hydrogen storage tank or the radiator (which could also be used to cool the vehicle’s power electronics), but it does include the stack and the supporting ‘balance of plant’ including its control electronics. The FC was trialled in the US Navy’s folded-wing XFC UAV, which was designed to fit into a torpedo tube. The torpedo is sent out of a submarine, comes to the surface, a hatch opens and out pops the XFC. Owing to the constraints of the torpedo tube the XFC had a 6 in diameter, a Protonex fuel cell for ScanEagle | Dossier Unmanned Systems Technology | June/July 2017 The ScanEagle prepares to launch with fuel cell power We use a PEM cell – there are alternatives but it is the most mature technology with the highest power density