There is plenty of discussion about future changes to aviation. New forms of propulsion are often cited as one of the likely major shifts. After all, standard fossil fuel-based fuels have been in use since the earliest days of aviation. Whilst hydrogen likely has more potential for large commercial aircraft; large-scale use is decades away. Electric propulsion, on the other hand, is already operational, with more use planned in the near future.
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The challenge with large electric aircraft
We will start with the limitations of electric propulsion – most significantly weight. With current, and predicted, battery technology, we are a long way from seeing large commercial aircraft operate with electric engines. Re-charging, of course, is not an option (as it is with ground transport), and aircraft will need large and heavy batteries for long flights.
Despite significant improvements in battery technology and energy density, use is still very limited. Current estimates are that for a 19-seat aircraft, the total range is just 160 miles (260 km), (according to Andreas Schafer, director of the air transportation systems lab at University College London). When reserve requirements for commercial flights are taken into account, this range is much less, potentially as low as 30 miles. For significantly better use, current energy density levels would need to quadruple.
One interesting opinion paper published in the journal Nature backs this up. Scientists claim that to power an aircraft such as the Airbus A320 or Boeing 737 narrowbody, current energy levels would need to go up by four or five times (to 800 watt-hours per kilogram). Added to this, they claim there will also need to be significant improvements in electric motors, battery discharge rates, and even aircraft aerodynamics. This is not years away; it is decades away.
Hybrid-electric is a possibility
For larger aircraft, hybrid electric use is a more likely possibility in the near future. This would see aircraft powered partially by electric, lowering emissions and making advances on green commitments.
Such development is to be encouraged too as commercial use will likely push research and development in the area, bringing full electric operation closer. As is often the case in early technology development, there have been commercial challenges so far, however.
Airbus is a leading manufacturer in the hybrid-propulsion area. Together with Rolls-Royce, it launched the E-Fan X demonstrator in 2017. This was a modified BAe 146 four-engine aircraft, with one turbofan engine replaced by an electric motor. The project was cancelled in 2020 due to the COVID pandemic. Airbus has also launched a program known as ZEROe to develop hybrid-hydrogen powered commercial aircraft by 2035.
Zunum Aero was another well-funded development, that shows how difficult commercial development is proving. It started in 2013, with proposals for a 50-seat regional hybrid-electric electric aircraft, with strong support and funding from Boeing and US airline JetBlue. Despite promising work on a 12-seat prototype, the company closed in 2019 when it failed to secure necessary additional funding.
Small aircraft well on the way
Battery technology, however, works for smaller aircraft, and commercial use is on the way. Cessna has developed the 9-seat Cessna eCaravan. This first flew in 2020, powered by a magniX electric engine. This offers a range of just 100 miles (less if it was in commercial use) – compared to 1230 miles for the standard Cessna Caravan. Similar and better uses in general aviation will no doubt follow.
Larger aircraft are being developed as well. Rolls-Royce is working with Norwegian airline Widerøe to develop an electric commercial jet by around 2026. This will have a capacity of 12 passengers and be used for short domestic flights. The Swedish startup Heart Aerospace is likewise working on a 19-seat electric aircraft known as the ES-19. This is also hoped to be certified by 2026, and has initial interest from airlines in Sweden, New Zealand, and Finland.
The short range works well with the mountainous or water geography in these areas; use in other areas will more likely have to wait for technical improvements.
eVTOL aircraft and air-taxis
The other use under development is electric vertical take off and landing (eVTOL) aircraft – often referred to with their excepted use of “air taxis”. Several companies are currently developing such aircraft (including start-ups as well as major aircraft manufacturers), although there has been minimal prototype developments so far.
Typical designs typically include a four to six person passenger cabin, battery powered engines, and a mechanism for vectoring thrust. The most common mechanisms are to pivot the rotors (so-called tilt-rotor), or to use flaps to direct airflow downwards from a fixed motor.
There are major additional challenges here with operating permissions, licenses, and legalities. This is a whole new area for general aviation and will require new operating rules and regulatory approval. Private or corporate use may be easier than full open commercial use, but there are still major regulatory, air space, and safety considerations to be resolved.
Logistics are a major consideration too. Such aircraft are unlikely to thrive at standard airports. Instead, city centre locations or rooftops are being considered. Platforms over water are another possibility for some cities.
Just as we are currently seeing with autonomous vehicle usage (requiring a similar whole new operating legislation and acceptance), eVTOL usage is likely to be phased in for specific uses and in certain locations. Although urban transportation and air taxis are the most talked about uses, there are also possibilities in cargo and freight, or military use.
Final Thoughts
In line with green considerations and policy, the aviation industry is taking an active interest in electric power. There are moves into larger aircraft, but the technology remains some way off. Developments of smaller electric powered aircraft, and eVTOL vehicles, which can maximise short range possibilities are well under way and we are likely to see commercial moves in the coming years.
Sources:
Quotes from Andreas Schafer: https://www.technologyreview.com/2022/08/17/1058013/electric-planes-taking-off-challenges/
Nature journal: https://www.nature.com/articles/s41893-019-0233-2.epdf
