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

60 Dossier | Spectronik PEM fuel cells hence causing considerable drops in performance. “Our internal testing has found that open-cathode cell power derates by 98% more than equivalent closed- cathode systems in 55 C environments,” Jap explains. “The closed-cathode architecture can therefore function safely in mission conditions that are not possible with open-cathode cells. “Our closed-cathode cells are rated to operate smoothly from -10 C to +45 C, and have been successfully tested to run from -15 C to +57 C. By comparison, most conventional open- cathode cells rarely operate well outside the 0-35 C range, and can suffer performance losses near the upper and lower ends of their temperature range.” Jap notes that having an additional blower in open-cathode architectures can sometimes mean a slightly higher balance-of-plant load (and therefore slightly higher power consumption), such as when running at around half maximum continuous power at room temperatures. However, net energy savings can be achieved when operating in environments below 5 C, and for UAVs carrying out deliveries or surveys over inhabited areas, the major gains in power stability and therefore safety are of far greater benefit than marginal changes in fuel consumption. “Also, the number of fans and blowers depends on the stack model,” he adds. “For example, the Protium-1000 has two fans and one blower, while the Protium-2000 has four fans and two blowers.” The specific power output of the closed-cathode stack is further improved by using a different filtering configuration than on open-cathode designs. When a single airstream is used for both cooling and supplying cathode oxidant, the entire face of the cell stack must be filtered to protect the cathode channels against contamination from dust and other particles. In the case of the Protium-1000, this is a surface measuring around 228 x 142 mm. By contrast, filtering the oxidant intake blower needs only a circular filter of about 32 cm in diameter – 1/40th the area of the cooling face on Spectronik’s Protium-1000, and a greater difference still on the larger systems, thus saving on weight and material costs. “Moreover, if you have to draw June/July 2021 | Unmanned Systems Technology The company’s latest UAV customer is the Phoenix hexacopter from Thunder Tiger Robotix Our internal testing has found that open-cathode cell power derates by 98% more than equivalent closed- cathode systems in 55 C conditions