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Cooling Innovations Enable Emergence of Commercial Electric Aviation in Island and Fjord Hopping
Although aviation is blamed for 3.5 percent of climate change, it is still the main missing puzzle piece in the promised carbon-free mobility future. Thermal challenges are standing in the way of commercial breakthroughs of fossil fuel-free, fully electric, rechargeable battery airplanes.
Governments have been funding research and development into electric aviation. Industry investments followed, including a lot of venture capital-funded startup buzz around eVTOLS, the snazzy electric vertical take-off and landing aircraft that mostly reuse the latest drone and electric vehicle (EV) technology. Actual widespread commercial use of electric aircraft, and certainly all-electric passenger jets, is still at least a decade away, despite political commitments in countries like Denmark and Sweden to have zero carbon domestic flights by 2030.
The trouble with electric aviation is mostly in thermal management. Turbines in fossil-fueled jet engines are only 35 percent efficient; 65 percent of the fuel’s power goes into heat and out of the exhaust, which at least easily solves much of the waste removal problem in traditional civil aviation, although that could still be an issue in military applications where you would prefer to remove the infrared heat signatures. Hydrogen fuel cells are a bit less inefficient at 50 percent, but require more elaborate cooling strategies, requiring big heat exchangers with weight-adding open areas.
Electric motors are much more efficient, but the amount of heat that needs to be removed at the power levels that airplanes require is still significant. The batteries also require cooling and stringent temperature controls to prevent packs from overheating and catching fire. In the car industry the rule is that the last line of defense for thermal runaway should give you at least 5 minutes to stop the car and get out safely. That would not work in airplanes. Batteries not only require cooling, but also heating or conditioning with intelligent, adaptive thermal management systems to keep them within a small temperature window where they operate optimally.
Airplanes can’t simply use the same technologies developed for electric vehicles (EVs), because batteries are just too heavy to provide all the power they need. The first generation of rechargeable battery-powered aircraft, with the battery technology that is available now and in the foreseeable future, will have very low range and not be able to fly between, for example, Berlin and Paris. The first certified electric-powered aircraft is the Velis Electro, a small two-seater for pilot training from Slovenian company Pipistrel that specialises in gliders and light aircraft.
The Velis Electro was certified in 2020 by the European Union Aviation Safety Agency (EASA), followed this year by a light-sport aircraft (LSA) airworthiness exemption from the American Federal Aviation Administration (FAA). The flyer produces zero emissions during operation, Pipistrel claims, and is ultra-quiet, with noise-levels of only 60 dBa inside and outside. Pipistrel has developed its own electric engine for the Velis Electro that produces 57.6 kW from a 345 volts direct current (VDC) electric system with an in-house developed dual battery system. The powertrain is entirely liquid-cooled and can be charged through an on-board charging port with an external charger.
Commercial electric aviation will first appear in similar niche applications, including scenic flights, skydiving, mountain hopping and – less likely… - city air taxis. Dovetail Electric Aviation is entering that market by first retrofitting existing aircraft, like the Cessna Caravan. The company was founded by David Doral, a Spanish engineer now living in Australia. Dovetail has operations in both countries and around 20 employees with plans to grow fast. The startup aims to develop its own electric power trains, fly experimentally next year with only batteries and certify their solution to start operations in 2026.
Ignacio Echavarria Diaz-Guardamino was asked to join Dovetail as CTO for his experience in both electric aviation engineering and certification processes. He previously worked for Airbus. ‘The idea is to get to market quickly by attacking a niche where electric aviation makes sense,’ he says, ‘and then at the same time innovate to allow more and more range.’ Dovetail’s first customers are Sydney Seaplanes and Scandinavian Seaplanes. Beyond island and fjord hopping, Ignacio does not exclude the option of city hopping in specific cases, like between Salzburg and Zurich to bypass the Alps or ‘between towns like Ingolstadt and Stuttgart, which are not well connected’.
Dovetail banks on future solutions that combine electric propulsion and batteries with hydrogen fuel cells and Sustainable Aviation Fuel (SAF). Airbus similarly aims to bring the world’s first hydrogen-powered commercial aircraft to market by 2035. Their fully electric CityAirbus NextGen prototype is scheduled for a first flight later this year. Airbus had earlier developed an EcoPulse hybrid-propulsion demonstrator aircraft with Daher and Safran. In June 2023, Airbus and STMicroelectronics signed an advance research agreement on the next generation semiconductors as a key enabler of the electric transition in aerospace. Next-generation semiconductor materials are essential to enhancing power efficiency and weight reduction.
JOIN US AT THERMAL MANAGEMENT EXPO EUROPE, STUTTGART, GERMANY, 3-5 DECEMBER
Ignacio Echavarria Diaz-Guardamino, CTO and Head of Engineering at Dovetail, will speak on a panel about the thermal challenges in electric aviation at the upcoming Thermal Management Expo conference, December 3-5 in Stuttgart.