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

104 Focus | Solar power angles, lends itself to the deposition of other materials with beneficial properties on top of and within the grooves. While these other materials were once regarded mainly as insulators, this design approach can use practically any materials of interest to solar cell producers. Before manufacture, the constituent materials used in perovskites are in a wet form, which enables them to be used flexibly in well-understood and easily controllable coating methods, such as blade coating, spray coating or slot die coating. The company has therefore built a printing machine in a pilot manufacturing facility to deposit perovskite inks. Once applied, the wet materials flow evenly across the microgrooves and are then dried to form the PV crystal structure. Through thesematerial and design selections, it aims to deliver a product optimised for the ratio of price versus solar conversion efficiency as a primary target, with ¢10 per watt at low-volume production and ¢5 per watt achievable at mass production, with anticipated efficiencies of 10-16%based on commercially viable technologies. By comparison, crystalline silicon tends to hover around ¢20/W, and thin-filmcopper indiumgalliumselenide around $0.50-1.00/W. Naturally, these manufacturing advantages also apply to other solar cell materials, be they single-junction perovskites applied to a substrate or dual-junction systems of perovskite on silicon. And although much of the growing use of solar across uncrewed systems has been single-junction systems, more manufacturing of dual-junction cells is expected, for the spacecraft industry in particular, as they can be more easily manufactured to reduce the solar absorptance – the fraction of total incident solar radiation absorbed by a cell – than other materials. That means they can avoid exceeding operating temperature limits for longer, and therefore, although they will lack the conversion efficiency of a triple-junction cell, their efficiency over their lifetime in space may well be superior. Multi-junction cell production chains can thus be expected to become more widespread, particularly perovskite-silicon dual- junction panels, as their coating and deposition methodologies mean they can be introduced into the production processes behind silicon cells, to enhance the resulting panels’ efficiencies, without changing very much at the factory level. There are various manufacturing methods for more conventional multi-junction solar materials, as opposed to crystalline silicon, which can be assembled layer by layer using straightforward mechanical approaches. These correspond mainly to differences in PV materials and combinations. Most follow a general pattern of cutting wafers of solar semiconductor from a large ingot and then carrying out chemical vapour deposition (CVD) of additional layers, such as secondary or tertiary-junction solar cells, anti-reflective protections, and back metals. The InGaP-GaAs-InGaAs triple-junction cell for instance relies on amethod called metal organic CVD, in which a release layer is deposited on a GaAs substrate, and then the solar cells and back metal are deposited on top. After that, the lattice- matched PV cells can be lifted from the substrate thanks to the presence of the release layer, and electrical and glass components can be added to the face of the PV cells to complete the panel. Moreover, the GaAs substrate can be reusedmultiple times, saving costs and reducing the environmental impact. Other forms of vacuum coating besides CVD are also used. For instance, one of the perovskite-focused approaches alluded to earlier is to use ‘sputtering’, a process in which atoms are ejected from a solid target material as a result of being bombarded by high- energy particles. This is a complex approach, but enables the highly controllable consistency and stoichiometry between material layers needed for optimising performance and longevity of thin-film solar cells at scale. In future, solar manufacturerswill face a trade-offbetweenmass-scale, low-cost production and smaller-scale, bespoke production. The uncrewed sector tends towards short production runs and small batches of vehicles, so the ability to tailor PV panels for different wing geometries, bus voltages and operating environments is key. Design and testing Developing a newsolar panel first requires information on the body of the uncrewed system. This is the ‘substrate’ onwhich the solar cells are to be laid, and therefore knowing the exact type of plastic, aluminiumor composite is key to understanding the electrical conductivity, thermal properties, chord dimensions February/March 2023 | Uncrewed Systems Technology More and more USVs integrate crystalline silicon solar panels, partially because of the material’s high moisture resistance among PV materials (Courtesy of Solbian)