Will an 'electric airplane' be put into practical use in the future?
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As hybrid and electric vehicles become more common, many people will be wondering, 'Will airplanes run on electricity in the future?' Duncan Walker , an applied aerodynamics researcher at Loughborough University , UK, describes the current state of electric airplanes as of 2019 and its future.
Electric planes are here – but they won't solve flying's CO₂ problem
https://theconversation.com/electric-planes-are-here-but-they-wont-solve-flyings-co-problem-125900
Many environmentalists are concerned about the fact that aircraft emit huge amounts of carbon dioxide, and in recent years an increasing number of activists have declared that they will not fly . Of course, it is normal to think that the wave of electrification is rushing into the aircraft industry as well as automobiles, but Walker pointed out that 'This is a complicated problem, and size is important.'
It is already possible to use electricity as power in small airplanes, and flight experiments with electric airplanes are actually being conducted. Walker acknowledges that small electric airplanes may hit the market in the coming years, but if a larger aircraft is being used by more people, it's hard to think like a small aircraft. It is not possible.
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The main barrier to electrification of large aircraft is not the propulsion system, but the energy density issue. It is said that the energy density of jet fuel used for aircraft will be 30 times as much as the latest lithium ion battery. Therefore, even if the jet fuel is replaced with a lithium-ion battery of the same volume as it is, the problem arises that the energy required for flight cannot be supplied.
For example, the world's largest airliner, the Airbus A380 , can fly up to 15,000 km with 600 passengers and cargo in a single flight. However, Mr. Walker pointed out that if the fuel of the Airbus A380 is replaced with a battery as it is, it will be able to fly just over 1000 km. Even if all passengers and cargo are replaced with batteries, the cruising range will only extend to less than 2000km. Even if the battery volume is increased by 30 times to maintain the conventional cruising range, it will be too heavy to take off this time.
This trade-off between weight and range is an issue for long-haul flights, as fuel takes up half of the takeoff weight of existing large passenger aircraft. In addition, the weight of the airframe decreases as jet fuel is consumed in a normal aircraft, but the weight of the battery changes little in an electric aircraft, so you must fly with the same weight from start to finish.
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It is said that while it is difficult to electrify large passenger aircraft, small-sized aircraft with 5 to 10 passengers, in which fuel accounts for about 10 to 20% of the total weight, can be relatively easily powered. Replacing existing fuel with a battery as it is would also shorten the cruising range, but for example, by reducing the passenger space for two to three people and using a battery, 500 aircraft that can fly 1000 km with conventional fuel will be 500 Walker says it can fly about 750 km.
Already, a startup called Eviation in Israel has announced an electric small aircraft named 'Alice' . Alice is not only replacing jet fuel with batteries, but also renovating the design concept by integrating the propulsion system into the fuselage. When scheduled to launch in 2022, it is said that it will be able to carry 9 passengers with a cruising range of 1000 km.
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Alice still focuses only on short-range flight of small aircraft, but Walker points to one possibility to further evolve electric planes, the presence of a ' lithium-air battery .' A lithium air battery is a battery that can be charged and discharged using oxygen in the air as the positive electrode active material, and can theoretically achieve the same energy density as jet fuel. However, at the time of writing, this is only an experimental stage, and there is no prospect of being installed in future aircraft.
While lithium-air batteries are far from practical, another more realistic alternative is a hybrid aircraft that combines an existing jet-fueled turbofan engine propulsion system with an electric propulsion system. This idea is being pursued by the demonstration electric hybrid propulsion system ' E-Fan X ', which is being jointly developed by Airbus , Rolls-Royce and Siemens .
In the E-Fan X project, plans are underway to replace one of the four turbofan engines with an electric motor driven propulsion fan using BAe 146 , a jetliner that can normally accommodate about 100 people. Have been Airbus is a hybrid aircraft technology to practical use until the 2030s, and you want to put into practical use in the 100-seater about airliner says .
In addition to battery improvements, the National Aeronautics and Space Administration (NASA) has proposed an idea of a `` blended wing body '' that is more efficient than conventional aircraft and integrally designed wing and fuselage . Major aircraft manufacturers are not actively pursuing the realization of the blended wing body because it requires large-scale design changes and many technical issues, but according to Walker, The dead wing body can reduce aircraft energy consumption by as much as 20%.
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After all, Walker says that there is no practical replacement for existing jet-fueled turbofan engines at the time of writing. For this reason, major aircraft manufacturers seem to be investing heavily in improving engine technology, and airline companies will invest as much as 1.3 trillion dollars (about 140 trillion yen) in aviation technology development in the next 10 years It is expected to rise.
For example, Rolls-Royce's latest engine, the Rolls-Royce Trent XWB, is described as 'the world's most efficient large aircraft engine.' The Airbus A350 XWB equipped with the Rolls-Royce Trent XWB 'has reduced operating costs, fuel consumption, and carbon dioxide emissions by 25% compared to the previous generation of aircraft,' the airlines said to existing jets. Walker said he was aiming to reduce carbon emissions while improving engine technology.
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