Uncrewed Systems Technology 046

78 I n UST 14 (June/July 2017) we featured the hydrogen fuel cell from the Protonex Technology Corporation, which at the time was principally used by Insitu as a swap- in replacement for the ScanEagle’s two-stroke spark-ignited engines from Northwest UAV and Orbital UAV. Since our first article on the technology, its commercial success has continued. More than a dozen UAV platforms and some UUVs now use the Protonex- designed PEMFCs, including the Solus-LR LUUV from Cellula Robotics (discussed in detail in UST 30, February/ March 2020), which is still a customer. We are therefore revisiting the technology to examine the current state of its design, subsystems and operation under its Honeywell ownership. At present, Honeywell offers two fuel cell products: a 1200 W system called the 1200U, and a 600 W system that comes in two versions. Of these, the standard-issue 600U is designed to output power at 12 to 33.6 V DC, with 30 A of continuous current up to peaks of 50 A, while the 600U-HV is designed for voltages from 8 to 58.8 V, and currents of up to 60 A continuously and 100 A at peak. Both can be referred to collectively as the 600U. The 600U weighs 1.8 kg, while its high-voltage variant is 1.9 kg. The 1200U weighs 4 kg, and while the 600U communicates over an RS-232 connection with its host platform’s autopilot, the 600U-HV and 1200U do so over RS-422 or CAN bus. All three have a time between overhauls – defined in this instance as the interval between replacements of the balance of plant (BoP) – of 1000 hours, and a service life of 3000 hours. “We’ve gone through extensive testing as it pertains to our different customer groups,” says Phil Robinson, senior director of engineering for zero-emissions aviation at Honeywell Aerospace (formerly VP of defence power systems and then of unmanned systems at Protonex, and general manager of the Ballard Unmanned US subsidiary as well). “For our Department of Defense (DoD) customer, for example, we’ve put fuel cells through Mil-Std electromagnetic testing to ensure we don’t interfere with other systems, as well as shock and vibration testing mainly for rough shipping, and even orientation testing where we show the fuel cell works for Rory Jackson looks at how this PEM technology has been developed since Honeywell took it under its wing Hydrogen Update October/November 2022 | Uncrewed Systems Technology The 600U is a 1.8 kg, 600 W PEM hydrogen fuel cell, outputting at up to 33.6 V, although a 58.8 V version is available (Images courtesy of Honeywell) The 1200U is a modular design that ‘doubles up’ two 600Us for a 1200 W hydrogen-electric power unit. They can be connected in series or parallel depending on the voltage needed