This is a modified Cessna station wagon 208B, which can accommodate up to 9 passengers. The test plane only installed one seat for the pilot.

　　Far from the 200-300-seat jet, this jet can take you on a weekend vacation or work trip in the city, and don’t mind the large double-decker plane across the continent. But the test flight of "eCaravan" was successful. The two companies behind it, AeroTEC and magniX, which supply motors, are dissatisfied with the results. Roei Ganzarski, CEO of magniX, pointed out in a statement that the price of flying Cessna is only $6 (4.80). If they use conventional engine fuel, the cost of a 30-minute flight is 300-400 dollars (240-320 pounds).

　　The first thing to note is that the long-distance flight of large aircraft will not become fully electric soon. Of course not in the next 50 years-the jury will discuss whether this will happen in this century. The reason is energy density.

　　Energy density is usually defined by watt-hours (Wh) obtained per kilogram (kg). At present, the energy density of lithium-ion batteries may reach 250 Wh/kg, while the energy density of jet fuel or kerosene is about 12,000 Wh/kg.

　　In this way, it seems that there is almost no hope for electric planes to catch up. However, this difference is not as obvious as it seems, because electric propulsion systems can be designed to be more efficient, which means they can cover more distances with less energy. However, at present, this still makes the energy richness of fossil fuel system 14 times higher than that of battery-powered alternative energy. The battery is not a liquid, it will not wander around, and it is also awkward in shape and volume. Susan Lay Liscout-Hanke, an aviation engineer at Concordia University in Montreal, said: "At present, this fuel is well integrated into the wing."

　　In addition, there is another obstacle that even if the battery is dead, the weight of the battery will remain the same. With the flight of traditional aircraft, kerosene is consumed, making the aircraft lighter. This in turn reduces the amount of fuel it needs to stay in the air.

　　Duncan Walker of Loughborough University has worked out what it means to actually send an electric plane into the air. He concluded that Airbus A380, the world’s largest passenger plane, can only fly 1,000 kilometers on batteries, while the standard flying distance is 15,000 kilometers. He wrote: "To maintain the current range, the aircraft needs 30 times the current fuel intake, which means it will never land."

　　These limitations mean that most industry experts believe that electrification of certain types of aircraft is the first step. This mainly means that they will be on the smaller side, but not necessarily very small.

　　Engineers are currently trying to build an all-electric jet plane that can accommodate 180 people and can fly about 500 kilometers. EasyJet, a low-cost airline, has cooperated with Wright Electric, an aviation startup, to design and develop this prototype aircraft. If successful, it can be put into commercial service as early as 2030. Its travel routes will be restricted-for example, from Paris to London, not according to Roland Berger, a management consultant, but narrow-body aircraft flying less than 1,500 kilometers account for about one-third of aviation emissions. By gradually introducing electric aircraft that can replace traditional aircraft in these short-distance trips, the impact of flight on the environment can be greatly improved.

　　Roland Roland Berger pointed out that the aviation industry is one of the main reasons for the sharp increase of carbon dioxide emissions in the EU. Although the aviation industry currently accounts for only 3% of global carbon dioxide emissions, due to the expected growth of this industry, by 2050, the emissions of commercial aircraft may account for 24% of global carbon dioxide emissions.

　　Robert Thomson, a partner of Roland Berger, said that it is "very ambitious" to commercialize all-electric 180-seat aircraft by 2030. A more sober view is that by 2030, we will be more likely to see the advent of hybrid electric aircraft. On these planes, power is provided by batteries and motors and traditional combustion systems. Thomson said: "A 50-seat plane will become a hybrid, maybe in 2030, that is, in the late 2020s-I think this is a reasonable timetable."

　　He added that his company has developed more than 200 electric aircraft, and the number of these projects increased by 30% between 2018 and 2019. Many of these planes are hybrid aircraft. Thomson said that they have a variety of "smells", of which electricity may only provide 10-20% of the aircraft’s propulsion. In principle, it may be easier to develop these designs using existing aircraft fuselages.

　　In recent years, one of the most concerned hybrid aircraft experiments is E-Fan X, which is a joint project between Airbus, Siemens and Rolls-Royce. The concept of the aircraft uses a 100-seat BAE 146 aircraft, which will be modified so that one of its four engines will be powered by a 2 MW engine-enough to power about 2,000 households. The plan originally planned to conduct a test flight this year, but the project was suddenly cancelled in April.

　　Riona Armesmith, chief project engineer of rolls royce’s hybrid propulsion company, said that the technology developed for E-Fan X has not been completely shelved. She said: "I think we just take a step back and see if we really need to use these systems." "I think we have learned enough knowledge."

　　Armesmith admits that there is no plan to use the technology of E-Fan X to fly another prototype plane, but we have learned a lot nonetheless. Most importantly, she said, components such as generators, cables and switching systems need to be redesigned or built completely from scratch in order to fly reliably and safely. It turns out that almost no one has ever modified the electrical system to fly an airplane of this size.

　　For example, electrical components need extra insulation to ensure that they will not catch fire, for example, Armesmith said. At high altitude, high voltage will cause greater damage to the insulation layer, so it must be very strong to be worth flying. This means that she and her team must design brand-new cables and switchboards. She said, "You can go,’ Ah, actually, it will be more challenging than we thought.’"

　　Rolls-Royce is also developing other experimental electric aircraft, including the all-electric ACCEL aircraft, which will start flying this year, aiming to set a record for the fastest electric aircraft. Although it is a small single-seater car, its design speed is close to 500 mph and its range is over 320 km.

　　Like many people in the industry, Amir Smith said that the biggest development may be to redesign the aircraft body to allocate more engines on the aircraft than usual. Theoretical research shows that using more and smaller engines can reduce drag and improve overall efficiency, thus making this kind of design a better choice for electric aircraft. This is one of the principles for Wright Electric to coordinate with EasyJet.

　　Liscout-Hanke said that a large number of projects and experiments on electric aircraft are still encouraging. This means that one of these planes has a better chance of success. Richard Aboulafia, vice president of analysis at Teal Group, an aviation market research company, added, but it is important not to be attracted by all the hype.

　　Although there is no doubt that the technical limitations faced by large aircraft are enormous, he praised the recent eCaravan experiment. There is a small market of about 100 small planes carrying a few passengers or some cargo every year. This kind of electric aircraft can work without changing the battery technology greatly, and it can carry out flight tests in fewer aircraft take-off and landing areas, which will eventually be safer. He said, "That’s the ideal testing market."

　　This will not excite those who dream of taking a holiday by electric jet (or those who live near a busy airport and want a quieter sky). But this may represent a key step towards this point.

　　At the same time, two other technologies under consideration to reduce aircraft emissions are biofuels and hydrogen propulsion systems. Everyone has their own problems. Biofuels made of organic substances can be used by existing aircraft and may be greener than kerosene. However, due to its small market scale, many biofuels have their own environmental disadvantages.

　　Thomson said: "The amount of hydrogen storage required by aircraft is about three times that of kerosene." "In today’s aircraft architecture, there is nowhere to put it."

　　In other words, these three promising technologies-batteries, biofuels and hydrogen-need to make some major breakthroughs before revolutionizing the aviation industry. The COVID-19 outbreak may further prevent the development of the situation.

　　However, people’s interest in environmental protection travel is being established. Liscout-Hanke said that with political support for electrification, the momentum behind the pilot projects of Airbus, EasyJet, Rolls-Royce and many other companies can be established.