Uncrewed Systems Technology 047 l Aergility ATLIS l AI focus l Clevon 1 UGV l Geospatial insight l Intergeo 2022 report l AUSA 2022 report I Infinity fuel cell l BeeX A.IKANBILIS l Propellers focus I Phoenix Wings Orca

89 Infinity APWR fuel cell | Dossier Thermal management and system control Infinity designs, develops, manufactures and programs its own embedded electronic control units for managing the cell stack and BoP, principally for monitoring each fuel cell for health conditions, intermittently venting inerts and water, and communicating health and performance information to external data buses. Each controller is designed for a mission’s required signal counts, data acquisition rates, memory rates and so on. The embedded software meanwhile implements Infinity’s algorithms for controlling the BoP and electrical output, achieving stable data storage and communicating operational parameters. Each version of the software is also validated and verified to the industry standards appropriate to the application, spaceflight standards being the most rigorous. The controller is typically mounted with the rest of the BoP – that is, the regulators and valves, as well as product water storage and potentially the thermal storage systems, depending on the application. “In some missions, such as the New Shepard-23, we were not allowed to increase the thermal load inside the pressurised capsule. Other missions, such as flight or lunar surface missions, are equally challenging,” Smith says. “With space being a vacuum, cooling is really difficult, as there’s nowhere for heat to go by conventional means. “To meet the New Shepard-23 requirement we needed to implement a thermal storage system. To do this we used a heat exchanger embedded in a wax-like phase change material [PCM], which absorbed the heat we created in the mission. The New Shepard-23 had a finite mission duration, so a PCM system could be defined. “Usually though, a fuel cell operating for an extended period needs to have a clear heat rejection pathway. For example, you can circulate water or some other fluid through the stack and route the water to that rejection spot, or for a UUV you have the sea around you as a great heat sink. So that New Shepard-23 PCM system was a very mission-specific creation.” As Infinity’s fuel cells are air- independent, it follows that they are closed-cathode systems, where the oxygen intake channel is not used for air- cooling. As mentioned, the four-chamber design includes a coolant chamber, through which liquid coolant (typically but not exclusively water) is circulated for every BPP, to achieve quick distribution and balancing of cooling across the stack, including in the humidifier section. “We reject the heat through that coolant loop to an external source. It can be another circulation loop, meaning a liquid-to-liquid heat exchange system, or we can use a cold plate in UUV as well as some space applications,” Smith says. Future plans As discussed, Infinity Fuel Cell and Hydrogen is now transitioning from prototyping and customising bespoke solutions towards a catalogue of productionised power system products for customers seeking scale orders. “We expect to have our beta-testing production units ready for interested parties to trial by the end of 2023, and then wide commercial availability in 2024,” Smith says. “Overall, we anticipate that the products will be extremely similar in architecture to what we’ve talked about here. However, as we collect new data from missions across space, sea and air, we’ll find ways to further optimise weight, ruggedness and performance, so we’ll have families of fuel cells suited to what individual users need in terms of form factors, currents, voltages, costs and so on.” Uncrewed Systems Technology | December/January 2023 Infinity base fuel cell PEMFC Length: 25 cm Diameter: 10 cm Weight: less than 6 kg Active fuel cell area: 50 cm 2 Number of fuel cell layers: 36 Nominal voltage: 28 V DC Maximum current output: 50 A Maximum power output: 1 kW Specifications In some cases, Infinity opts to integrate as much of the balance of plant into the end plates as possible, simplifying integration and mounting duties for the end-user