Unmanned Systems Technology 038 l Skyeton Raybird-3 l Data storage l Sea-Kit X-Class USV l USVs insight l Spectronik PEM fuel cells l Blue White Robotics UVIO l Antennas l AUVSI Xponential Virtual 2021 report

58 H ydrogen is rapidly being adopted across unmanned systems as an energy carrier and power source, and new designs and technologies for hydrogen fuel cells are accordingly being commercialised for UAV manufacturers and operators in civil, industrial and defence markets. One of the most widely discussed of these is the closed-cathode proton exchange membrane (PEM) fuel cell. Unlike open-cathode PEM fuel cells, which use the same airstream for reaction and cooling, closed-cathode systems are designed with separate cooling and oxidant channels. As thermal management and oxidant supply are two different systems with very different efficiency considerations, running them separately by way of a closed-cathode architecture can greatly enhance the performance and safety of PEM cells. While some closed-cathode fuel cells have been made principally for space and UUV applications (such as Teledyne’s EDR fuel cell, featured in UST 35, December 2020/January 2021), Singapore-based Spectronik has developed its cell architecture for high- end UAVs and new automotive systems. Although the company also offers open- cathode cells (see sidebar on page 63) it has devoted several years of r&d to optimising its Protium series of closed- cathode cells for greater operational safety, stability of performance, longevity and other critical parameters compared with conventional open-cathode types. It currently offers four closed- cathode products. The smallest is the Rory Jackson investigates this range of closed-cathode fuel cells, which offer better performance than open-cathode systems Closed circuit June/July 2021 | Unmanned Systems Technology Spectronik makes a range of closed- cathode fuel cells, its smallest being this, the Protium-1000, which gives an output of up to 1.2 kW (Images courtesy of Spectronik)