Uncrewed Systems Technology 048 | Kodiak Driver | 5G focus | Tiburon USV | Skypersonic Skycopter and Skyrover | CES 2023 | Limbach L 2400 DX and L 550 EFG | NXInnovation NX 100 Enviro | Solar power focus | Protegimus Protection

100 M any UAVs and USVs now come fitted with solar panels covering much of their surfaces. The interest in solar energy comes frommore than it being a potentially limitless source of green power; for uncrewed systems it extends autonomy in a practical sense. For many electric UAVs for instance, the bulk of hands-on maintenance has been reduced to swapping a fresh battery into the chassis (repairs and overhauls notwithstanding). But if a UAV can land in a field and sit while being recharged by sunlight then maintenance technicians don’t need to lift a finger. Much like satellites or the uncrewed systems on Mars, the vehicles can take care of themselves thanks to their solar panels. The most prominent examples of autonomous systems using solar cells include high-altitude, long-endurance (HALE) pseudosatellite platforms. The Airbus Zephyr and BAE Systems’ PHASA-35 projects are perhaps the most widely known of these, the former having set a new world record for autonomous flight endurance last summer thanks to its specific selection and integration of solar cells. Several more HALE UAVs are now also being developed by other companies. These aircraft are intended to fly in the stratosphere for around a year at a time, where light interference will be minimised during the day, and lift is maximised by using a very large, high aspect-ratio wing to provide plenty of area for photovoltaic (PV) cells to be integrated as a less weighty source of power than batteries. Trying to supply themwith energy from batteries alone for 365 days would soon render them unfeasibly heavy. Similarly, long-endurance USVs from companies such as Saildrone, Mayflower and AutoNaut (see UST 38, June/July 2021; UST 42, February/March 2022; and UST 12, February/March 2017 respectively) are packed with solar panels for replenishing their batteries while sitting relatively stationary in mid-ocean. While weight reduction is less mission- critical for sea vessels, the space saved in their hulls by exchanging battery volume for thin solar panels enables more electronics hardware for research, mapping and comms relay missions, enhancing the usefulness of these vehicles and the return on investment from their voyages. Beyond these, however, there is a wide and growing array of short to medium endurance electric uncrewed systems that are at least partially solar-powered. This has come from PV technology advancing and maturing to the point that it is not only accessible to smaller companies from a cost perspective, but also worthwhile for enhancing performance, with the most important performance parameters varying according to the use case. Multi-junction cells Power density (wattage relative to volume) and specific power (wattage relative to mass) remain the most critical factors for high-end, long-endurance users considering installing solar cells on their uncrewed systems. Both specifications tie in with solar conversion efficiency – that is, the amount of sunlight transmitted into the cell and turned into current, rather than being reflected or lost as heat. While there are Saving weight in uncrewed systems is only one benefit of solar power, writes Rory Jackson , who reports on advances in the technology Travelling February/March 2023 | Uncrewed Systems Technology