Electric airplanes have reached another milestone, and the question is, how much longer can it take to be ready for everyday flight? And how far will they be able to fly?
At a large airport in central Washington, surrounded by vast land, an electric plane recently made history. It is the largest commercial aircraft ever to take off and fly with electric propulsion only. On May 28, 2020, it rose above Grant County International Airport for a 30-minute period, amid applause and merriment from a crowd of spectators. The largest electric plane ever? Well, it was a modified Cessna Caravan 208B – capable of accommodating up to nine passengers. And the test aircraft had only one seat for the pilot. This is far from the 200-300-seater plane we travel to for weekends, city breaks or work, not to mention the huge double-decker planes that cross the continents. But the test flight of the “eCaravan” was a success. The two companies behind things, AeroTEC and magniX, which supplied the electric motor, are pleased with the results. Roei Ganzarski, CEO of magniX, said the price of Cessna’s flight was just $ 6 (£ 4.80). If conventional engine fuel had been used, a 30-minute flight would have cost $ 300-400 (£ 240-320).
This test flight was built on previous experiments with a smaller aircraft that was also equipped with an electric motor manufactured by magniX. And the question arises: when are we going to fly a larger passenger plane that does not run on fossil fuels but on electricity? The first thing to note is that long-haul flights with large aircraft will not soon become fully electric. Certainly not in the next 5 years, but still in this century. This is due to the density of energy. Energy density is usually expressed as the number of watts (Wh) you get per kilogram (kg). Current lithium-ion batteries have an energy density of up to 250 Wh / kg, while jet fuel or kerosene has an energy density of about 12,000 Wh / kg.
Electric planes seem to have little hope of catching up. However, the difference is not as terrible as it seems, as electric drive systems can be designed to be more efficient, meaning they can do more miles with less energy. However, the current situation continues to make fossil fuel systems about 14 times richer in energy than battery-powered alternatives. Batteries that cannot be arbitrarily disposed of as liquid are also inconvenient in shape and bulk. “Right now, the fuel is getting nicely into the wing,” says Susan Liscouët-Hanke, an aeronautical engineer at Concordia University in Montreal. To maintain the current flight range, the aircraft would need as many batteries that weigh 30 times the weight of current fuel consumption, meaning it would never rise off the ground, Duncan Walker said. In addition, another obstacle is that the weight of the battery remains the same even if it is worn out. As a traditional airplane flies, kerosene wears out, making the airplane lighter. This in turn reduces the amount of fuel needed to stay in the air.
Duncan Walker of Loughborough University, one of those who calculated what this means in actually putting electric planes into the air. It turned out that the world’s largest passenger aircraft, the Airbus A380, can only fly 1,000 kilometers with batteries, compared to the usual 15,000 km. “To maintain the current flight range, the aircraft would need as many batteries that weigh 30 times the weight of current fuel consumption, meaning it would never rise off the ground.” – writes. These limiting factors mean that most industry experts believe there are special types that need to be electrified first. This primarily means that they will be small, but not necessarily small.
Engineers are currently trying to build a 180-seat all-electric jet capable of flying about 500km. The low-cost airline, EasyJet, in partnership with Wright Electric, the start-up airline, will design and develop a prototype aircraft that, if successful, will enter commercial service as early as 2030. Its travel routes will be limited – not much longer between Paris and London, for example – but narrow-body aircraft, which fly shorter distances of up to 1,500 km, account for about a third of aviation emissions, according to management consultant Roland Berger. By gradually introducing electric aircraft, which can replace conventional aircraft on these short-haul routes, the environmental impact of aviation can be significantly improved.
However, this will not happen soon because, as Roland Berger notes, aviation is the only major industry in the EU where CO2 emissions are rising significantly. Although the industry today accounts for only 3% of global CO2 emissions, by 2050 commercial aircraft could reach up to 24% of global emissions due to the expected growth of the sector.
The fully electric 180-seater aircraft planned to fly by 2030 is “very ambitious,” said Robert Thomson, partner at Roland Berger. Common sense suggests that by 2030, hybrid electric aircraft are likely to be on the market. In these aircraft, propulsion is provided by batteries and electric motors, in addition to conventional combustion systems. “A 50-seat aircraft would be viable as a hybrid, maybe by 2030, by the end of the 2020s – I think that’s the kind of time frame that’s likely,” Thomson says. He adds that his company has been involved in the development of more than 200 electric-powered aircraft, and the number of these projects increased by 30% between 2018 and 2019. Most of these aircraft are hybrid models. They are in all sorts of “choices,” Thomson says, where electricity can provide only 10-20% of an aircraft’s propulsion. Nevertheless, in principle, these plans can be easier to develop using existing aircraft bodies.
One of the closest-observed hybrid aircraft experiments in recent years is a joint project between E-Fan X, Airbus, Siemens and Rolls-Royce. The aircraft’s concept included a 100-seat BAE 146 aircraft that had to be modified so that one of its four engines was powered by a 2-megawatt engine – enough energy to power about 2,000 houses. The plan was for the aircraft to carry out a test flight in 2021 this year, but the project was abruptly halted last April.
The biggest improvement can happen when the body of an aircraft is redesigned to have more engines than usual. Riona Armesmith, chief engineer at Rolls-Royce’s hybrid electric drive, said the technology developed for the E-Fan X wasn’t entirely up to it. “I think we just took a step back and looked at whether we really needed to fly these systems,” he says. “I think we felt we’ve learned enough.”
Armesmith admits that there are currently no plans to fly another prototype aircraft using E-Fan X system technology, but they have learned a lot from it nonetheless. Last but not least, how components such as electrical generators, cables and switching systems need to be redesigned or built from scratch to be reliable and safe to fly, he says. Truth be told, hardly any electrical systems have been used to service aircraft of this size before. Electrical components require additional insulation to ensure they don’t cause a fire, for example, says Armesmith. And at high altitudes, high voltage takes greater advantage of this insulation, so it has to be very robust to be suitable for flight. This meant he and his team had to design brand new cables and switchboards. “You have to move on somehow, in fact, it’s a much bigger challenge than we thought,” he says.
Rolls-Royce even has experimental electric aircraft under development, including the all-electric ACCEL aircraft, which is expected to have a test flight this year with the goal of setting a record as the fastest electric aircraft. Although small, it is designed for speeds of nearly 500 km / h and can cover distances of more than 320 km. Like many in the industry, Armesmith says the biggest improvement can happen when the body of an aircraft is redesigned to have more engines than usual. Theoretical studies suggest that using more, smaller engines can reduce inertia and improve overall efficiency – such designs have the potential to provide better options for electric aircraft. This is one of the principles of Wright Electric’s work coordinated with EasyJet.
According to Liscouët-Hanke, the huge range of projects and experiments related to electric aircraft remains encouraging. This means that there is more chance of success for one of these aircraft. However, it is important not to get caught up in all the hype, ”added Richard Aboulafia, vice president of analytics for aviation market research firm Teal Group. While the technological limitations associated with larger aircraft are undoubtedly significant, it still praises the recent eCaravan experiment. For small aircraft that carry a handful of passengers or little cargo, there is a small market with about 100 vehicles a year. These types of electric aircraft do not require major changes in battery technology to operate, and flights can be tested in less built-up areas, which is ultimately safer. “This is the ideal test market,” he says.
It doesn’t excite people who dream of vacationing on an electric jet (or those who live near busy airports, hoping for a quieter sky). But it may represent some critical baby steps on the road to the goal. Meanwhile, two other technologies have been studied to reduce aircraft emissions, biofuels and hydrogen propulsion systems. Each has its own problem. Organic biofuels can be used by existing aircraft and may be greener than kerosene, yet the market is small and many biofuels have their own environmental disadvantages. And hydrogen, while potentially pure when obtained from a renewable source, suffers from the same problem as electric batteries. “There’s something needed to store hydrogen in an aircraft, which is three times the space required for kerosene,” says Thomson. “Given today’s aircraft architecture, nowhere can this be placed.”
In other words, all three elements of promising technologies – batteries, biofuels and hydrogen – require major breakthroughs before aviation can be revolutionized. And the Covid-19 pandemic, which has hit the aviation industry very hard, could further delay developments. However, interest in more environmentally friendly travel is growing. With the political support of electrification, the momentum of Airbus, EasyJet, Rolls-Royce and many other pilot projects can be used, says Liscouët-Hanke.