Unmanned Systems Technology Dec/Jan 2020 | Phoenix UAS | Sonar focus | Construction insight | InterGeo 2019 | Supacat ATMP | Adelan fuel cell | Oregon tour | DSEI 2019 | Copperstone Helix | Power management focus

62 A s UAV markets grow, propulsion engineers have witnessed a soaring demand for multi-fuel power systems that can act as hybrid electric range extenders to increase flight times while minimising operating costs. That provides opportunities for solid oxide fuel cell (SOFC) developers. These operate on similar principles to proton exchange membrane fuel cells (PEMFCs), but while PEMFCs must generate energy using hydrogen – typically pressurised hydrogen gas – SOFCs can use almost any fuel that contains hydrogen, including a wide range of hydrocarbons and biofuels. SOFCs have historically been touted as large, stationary systems for generating megawatts of power. However, UK company Adelan and its CEO Dr Michaela Kendall have pioneered a unique form of the technology, the microtubular solid oxide fuel cell (mSOFC). Dr Kendall and her colleagues see it as better suited to smaller form factors for relatively light vehicles, such as UAVs and UGVs. The mSOFC improves significantly over its SOFC predecessors in terms of design flexibility, form factor and time to start up. The long, thin shape of the cell and its power-to-volume ratio lend it towards applications in fixed-wing UAVs in particular (rather than multi-rotor systems, for example), Dr Kendall says. Also, the company has participated in independent field trials and lab tests comparing the operation of different fuel cells – specifically mSOFCs, PEMFCs and direct methanol fuel cells – in terms of running time, cost per kWh and Wh/kg. “While PEMFC technology has the advantage in power density [kW/kg] it A unique take on the solid oxide fuel cell holds great promise for fixed-wing UAVs. Rory Jackson explains how it works It’s all in the tubes December/January 2020 | Unmanned Systems Technology The microtubular solid oxide fuel cell can use a range of fuels to extend the endurance of fixed-wing UAVs as well as UGVs (Images courtesy of Adelan)