Electromobility in the air
Electric aircraft - an alternative for the aviation industry? The elimination of environmental factors such as noise levels and air pollution is one of the biggest advantages of electric engines.
© Florian Wagner, Wagnerphoto.de
Electrically powered aircraft can revolutionize the aviation industry. The elimination of environmentally harmful factors such as noise levels and air pollution also means more flexibility in building airports near residential areas. A reduction in fuel and maintenance costs could increase the economic efficiency of smaller aircraft and thus open up further advantages.
Representatives from politics and industry agree that alternatives to conventional propulsion systems in aviation must be created. This means that the industry is facing a centenary task, because it is easier to plan than to do away with "old" concepts and create innovative possibilities.
Electric mobility in aviation
As in the automotive sector, an obvious solution is electric mobility. The question of whether humans can fly in an electric aircraft has been answered decades before. Innovations in aviation essentially follow the paths which have already been paved by land-based transport. An electric drive system provides for the propulsion of electric aircraft, either as a hybrid variant or as a full replacement for conventional turbines. Just as in a car, the power source is either a battery, a fuel cell or a solar cell. The advantages of electric mobility for the air are obvious as well. On the one hand, aircraft components are becoming increasingly lighter thanks to new manufacturing processes, such as additive manufacturing. The same is also being sought for batteries, which are also expected to have a better energy density in the future. In addition, electric motors will become more efficient. Siemens has already developed a motor with 5 KW output per kilogram of weight. Another very powerful argument for the economy is also the reduction of maintenance work and thus costs.
A well-known electric aircraft project is the Extra 330LE. Siemens is using this aerobatic aircraft to develop powerful electric motors that will be used in aircraft with 20 or more seats. The aim is to develop hybrid drives with a range up to 1,000 kilometers. Since its maiden flight in 2016, the Extra 330LE, powered by the 260-kilowatt and 50-kilogram Siemens SP-260 DP electric motor, has set several records and is the first electric aircraft to tow a glider.
The Her0 is also declared as "Tesla of aviation" in the industry and originates from the pen of the designer Joe Doucet. The electrically driven propellers and wide wings allow for economical gliding and completely emission-free flying. However, this costs the travellers some speed. Because with about 700km/h the jet is only almost as fast as the non-emission-free competition. But this also means that about 20 percent additional time must be planned for travel. According to the developer, however, this aspect does not prevent the advantage of zero emissions. Doucet also emphasizes that his design should only be seen as a thought-provoking impulse for the future of aviation. The Her0 is not planned for series production.
Solar aircraft - an alternative?
Using solar energy for airplanes is very attractive. An efficient use of solar energy is much more possible in a solar airplane than in a car. There are many advantages due to the altitude of the flight, such as shadowless zones, low solar radiation absorption by the earth's atmosphere or an ever thinner layer of air.
However, even a solar airplane needs a battery for night operation and for the arising peak loads that occur, for example, during take-off and climb. A battery always means weight and is also a potential source of danger. Lithium batteries, for example, are criticized in this respect because they can easily catch fire. There are many reasons for this, ranging from thermal influences, water contact, short circuits and overcharging. The requirement for a good battery is currently one of the greatest technical challenges in all industries. In addition, a very efficient motor is needed to ensure that the energy does not run out.
Innovation Solar Aircraft: SolarImpuls2
The Solar Impuls 2, a Swiss solar aircraft, has four engines with an efficiency of 94%. These are connected to lithium-polymer batteries to provide an uninterrupted power supply. These batteries are charged by 17,000 solar cells. This is a great machine, but it is unlikely to be used in passenger aviation, as it can carry nothing in the air except its own weight and the weight of the pilot. In 2016, Bertrand Piccard succeeded in a historic flight around the world. During the 510-hour journey, the SolarImpuls2 covered a distance of about 40,000 km using only solar energy. The developer himself explains: "SolarImpuls was not built to transport passengers, but to convey messages. We are not planning a revolution in the aviation industry; instead, we want to show that alternative energy sources and new technologies can be successful, which some thought impossible".
Alternative fuel cell
Already 8 years ago, the German Aerospace Center (DLR) presented a fuel cell powered nosewheel, which was installed in the DLR research aircraft A320 Atra. The HY4, a four-seater of the institute, is a daring experiment. The technology of the HY4 is based on a hybrid system. A low-temperature PEM fuel cell is used as the main energy source. Since this energy is not sufficient during take-off, the aircraft also relies on a lithium battery. These two energy producers supply an 80KW strong engine with enough energy to take off safely, fly up to 200 km/h and cover more than 1,000 km long distances. The airspeed is certainly still expandable, but the HY4 can already transport four people and a further development is well conceivable.
Future "made in Germany"
In 2050, the traffic axes of many metropolises are expected to have reached their capacity limits. Commuters and business travellers will be stuck in traffic jams, losing working and living time. This problem calls start-ups and established aviation companies from all over the world equally to the scene. With innovative aircraft - mainly electrically powered - the engineers want to solve the traffic problems by air. The common goal is to get from A to B quickly, without traffic jams and at low cost.
With the maiden flight of the Volocopter VC1 from Karlsruhe in 2011 the feasibility of a vision was proven. In March 2016, Alexander Zosel, co-founder of Volocopter GmbH, took off for the manned maiden flight in the open air. The first production model is the VoloCity, which is now also equipped with vertical stabilizers to stabilize the flight direction. It is also designed to comply with the SC-VTOL regulations of EASA, which were published in July 2019.
In 2015 Daniel Wiegand and three other students of the University of Munich founded Lilium GmbH. The electrically driven Lilium Jet is powered by 36 ducted propellers mounted in movable flaps on wings and fuselage.
In April 2017 the prototype of the two-seater took off for its unmanned maiden flight. In 2025, it could take off as an air taxi. Flights at the price of a taxi ride are to be booked via app; landing pads on buildings are planned. At the end of 2019, the first production hall with an area of approx. 3000 m², next to the company headquarters, will be ready for series production; another one is already being planned.
Europe's aviation giant shows its creativity
CityAirbus is the name of a study for urban use. "The electric vehicle for around four passengers resembles a drone with several lifting rotors. In the initial phase, a human pilot on board would take over the control, partly because of current regulations for passenger transport, but later purely automatic operation would also be possible," reported FLUG REVUE in summer 2016.
A3 (pronounced "A-cubed") is the name of an Airbus subsidiary based in Silicon Valley. Engineers are developing an autonomous single-seater named Vahana with eight rotors mounted on swing-wings. The final version is scheduled to take off in 2020.
In Slovakia, experts are researching on the AeroMobil - a flying car. The makers of Pop.Up are pursuing a similar approach. This symbiosis of car and multicopter consists of a chassis for the road, a cabin for two passengers and a flight module with eight counter-rotating rotors. The feasibility study was developed in cooperation with Italdesign. In addition, the Group is working on a regional aircraft with hybrid drive; however, the electric aircraft E-Fan is not being further developed.
Challenges for electric mobility
Conventional passenger aircraft today use highly developed turbines. Some of them consume several liters of kerosene per second, but are capable of transporting more than 200 passengers quickly (at e.g. 1,000 km/h) and safely to their destination. When these turbine forces are converted for an electric motor, the developers and engineers face a challenge in the megawatt range.
Talking about innovations, progress in classical aviation should also be taken into account. Turbines are constantly being further developed, the geared turbofan engines are becoming quieter and more efficient. Electric aircraft must also be able to measure up to these advances. In addition, the airport and logistics infrastructure is designed for conventional aircraft. At airports, additional infrastructure for electric aircraft would have to be developed.
The next 10 years will show whether and how electromobility will become established in civil aviation. Today it can already be said with assurance that electric aircraft will be an enrichment for aviation. In any case, the European Aviation Safety Agency (EASA) has long been dealing with the topics of electric flight and air traffic of the future. A project, which affects general aviation as well as large aircraft, was initiated within the authority. It deals with type certifications, construction rules and regulations for the operation of aircraft. "We have decided to avoid the process of drawing up new regulations, but to take better account of the concerns of operators and companies by adapting the existing regulations together with the national authorities," says EASA spokesman Dominique Fouda in a statement. Applications for certificates had been received and initial coordination talks had also taken place. "The EASA management has confirmed that these innovative projects should receive full support".