83 energy density of batteries is still a problem for aviation,” Kahnert says. “You quickly hit a physical limit when trying to achieve a long-range flight with a heavy payload using batteries alone, even if an all-battery powertrain is appealingly simple.” EFT has therefore sought to develop its first product as a plug-and-play hybrid-electric solution principally for heavy UAV manufacturers, with the aim of combining the maturity, power density and energy density of an IC engine with the ease of use of an all-electric solution, in addition to having lower emissions compared with an IC powertrain. That first product is the EFT-Hybrid1x, a 19.5 kg gasoline-electric serieshybrid powertrain, which produces 11.7 kW of continuous electric power. It has no intended shaft power, as its primary customers are manufacturers of multi-rotors and other all-electric UAVs seeking higher endurances than batteries alone can offer. The IC engine at the core of the solution has a specific fuel consumption of 290 g/kWh and is produced by Salzburg-based engineering company HC-Concepts, which also provides key development support across prototyping, testing, and industrialisation for EFT. The engine is a modification of what HC-Concepts refers to internally as the AX250. This is a four-stroke, sparkignited two-cylinder boxer running on gasoline. However, as EFT’s engineering is aimed at providing an electrified product, and as HC-Concepts is not principally a UAV engine company, we will focus here more on the electric componentry in the powertrain, as designed by Kahnert and his team, along with some critical contributions from Acutronic Power Systems, formerly Sulllivan UV. The most visible of these components in the Hybrid-1x’s configuration are an alternator – the preferred nomenclature from EFT and Acutronic, rather than ‘generator’ or ‘motor/generator’ – which is mounted on the output shaft in front of the engine, and a forced-air cooling system mounted in front of and around the alternator (as well as over the engine cylinders). Downstream from the alternator are a power management unit (PMU) that connects with the alternator, rectifies its AC output into DC (and can invert DC to AC to power the alternator for starting the engine), and is mounted wherever the end-user thinks is prudent in Electric Flytrain EFT-Hybrid-1x | Dossier You quickly hit a physical limit when trying to achieve a long-range flight with a heavy payload using batteries alone, even if that is appealingly simple Uncrewed Systems Technology | June/July 2023 About 50 hours of endurance testing have been completed to prove-out the EFT-Hybrid1x’s long-term performance capabilities
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