Categories: AnalysisNotification

Don’t Expect To See Large Electric Planes Until At Least 2040

When the opportunity was presented to hear whether large electric planes are a myth or reality, I knew I had to listen carefully. The topic of electric aircraft often leads to heated debate on Simple Flying, so I hoped this would put things into context. Here’s what I found out.

Why aren’t we all flying about in electric planes yet? Photo: Airbus

Where are all the electric planes?

Electric planes are a hot topic right now. I mean, it seems a simple solution to all the climate change, flight shame concerns that the industry has right now; just stick a battery in it, right? They’ve done it with cars, so…

Unfortunately, real life is not as simple as that. Sure, an electric aircraft on paper is an all-round winner. It would be quiet, reduce CO2 emissions locally and the actual engine/motor part would be far less complex. That would make it easier to maintain and is less likely to go wrong. The problem is, you can’t just stick a battery into a regular plane.

Andreas Klöckner, Coordinator Electric Flying Program Strategy Aeronautics at the German Aerospace Center (DLR) illustrated the problem at the recent IATA Wings of Change conference with this image:

Andreas Klöckner shared a scale representation of how big a battery would have to be to power a commercial jet. Photo: Simple Flying

To get a typical narrowbody off the ground with today’s battery technology, as you can see, would be impossible. The battery would be enormous. It would add huge amounts to the weight too. Mark Dunnachie from ATR said as much at AviaDev this year, stating that a battery weighing 20 tonnes would be required for an ATR aircraft, which is roughly equal to its MTOW.

So, right now, it’s no more possible to turn a large passenger plane into an electric plane than it is to solve climate change by sailing across the Atlantic.

What can be done now?

Nevertheless, there has never been more action in the field of developing electric aircraft than there is right now. In fact, there are a few working models out there, and one which has even gained its FAA Certification. The Pipistrel Alpha Trainer seats one person and has a range of around 373 miles (600km). Good for pilot training schools, but not much else.

The Pipistrel Alpha trainer. Photo: New York-air via Wikimedia

Moving up to something larger, Eviation is working on a nine-passenger electric plane called Alice. They are looking to gain FAA approval by 2022, but with such a small capacity for pax and a range of just 650 miles (1,046 km), it’s still not going to be the commercial aircraft replacement we need.

The Eviation Alice is a fully electric aircraft, but only for nine passengers. Photo: Eviation

These existing aircraft use some few hundred kilowatts of power; the next step is to move towards a megawatt of power. Andreas explained where the next step from here would be.

This demonstrator commuter plane is used by DLR to test new technology. Photo: Simple Flying

“This aircraft has half a megawatt on each side, so that’s a good step towards testing new technologies. This will still be just a demonstration aircraft, to test various new tech as it comes along. As a product, it might be there by the end of the 2020s,” Andreas commented.

What about large electric aircraft?

To begin looking at replacing the gas turbine powerhouses required to move something bigger is a step up again. Andreas explained,

“If we then go even bigger and look at the workhorse A320, that will take some time. That will probably also take some new technologies. We’re thinking fuel cells here, which are not ready yet, but would be needed to fly something of such a large size.”

Not only is the technology not quite ready for a large electric passenger plane just yet, but the plane that it ends up being might not be quite like we’re used to. Andreas shared some images of how an electric plane could eventually appear.

It’s a plane, Jim, but not as we know it. Photo: Simple Flying

“We would also need to take advantage of all the configuration benefits that we can generate. Things like boundary layer or distributed propulsion; all of these will probably need to be integrated into the aircraft. Because a large aircraft like this, if you want to make it electric, you’re really at the limit of technical possibilities.”

Taking all that into account, we’re clearly a long way off a working electrified large aircraft. But how far off? Andreas took a stab,

“What would be the timescale for this? We’re thinking maybe 2040; something like this.”

As well as developing the actual aircraft design, there’s a whole load of infrastructure development that’s got to go on behind the scenes in order to make electrification of flight a workable possibility. Charging up electric aircraft by fossil fuels would be a false win, and even getting the charging facilities of the right numbers at the right airports poses a logistical challenge.

That’s not to say we will never have a large electric passenger plane; only that it won’t be happening any time soon.

This post was last modified on November 28, 2019 7:09 pm

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  • Sheeples, the ruling elite are laughing at you. Do you think there is no technology that can build a lightweight strong, fuel efficient car or aircraft that doesn't run on 80-100 year old petrol burning technology?

    • Another idealist that thinks that technological innovation just falls out of the sky...like the Sword of Gryffindor in Harry Potter...
      Let me guess: you think that the technology is already there, but that there's a conspiracy to keep it out of production...right?

      • I can assure you that most technology development is carried out in secrecy, especially for the military and companies with huge investments at stake.
        The IPhone is a good example of technology designed deliberately to expire and be "upgraded" every 2 or 3 years, the Lockheed skunk works a good example of what can be hidden for decades without public knowledge.
        The trickle of technology is part of the supply and demand, consumer society we live in.
        Ps sorry but I have not seen Harry Potter.

  • Here's a concept for a liquid hydrogen powered A320-sized aircraft:

    Polaris - Future Aircraft Design Concept

    https://www.dlr.de/dlr/Portaldata/1/Resources/documents/2018/Universitaet_Stuttgart_Polaris.pdf

    -

    Abstract

    Looking at aviation in 2045 a competitive operation of aircraft will not only be dependent on highly efficient aircraft, but also on passenger comfort, manufacturing effort and an excellent life cycle. The present report provides a breakdown of an aircraft design study with consideration of future aviation goals and proposals that might further improve the design with regard to pollutant and noise emissions.

    An adjusted design process is used to find the synergies of all components and to combine their advantages instead of evaluating each component itself. Correlating with the design process, the final aircraft design is discussed with its results, options and challenges. To validate the quality of the results, the reference aircraft CSR-01 (A320) is emulated in relation to energy consumption, mass estimation and aerodynamics with a deviation of less than 1 %.

    With special remark to the used key technologies the report provides information about current technical states, future improvements and an estimation of their qualitative efficiency in 2045. Except for high temperature superconducting (HTS) material all other used technologies are at least tested on a demonstrator or available for series production by now. HTS materials currently attain technology readiness level 4 and therefore illustrate that the used key technologies of this aircraft design are about to be available before 2025.

    Finally, the improvements of this design are based on the synergistic integration of each component, resulting in a single-aisle transport aircraft that reduces the energy consumption for an equal mission by 61.39 % in reference to an A320 in 2005. A multi-functional fuselage concept combined with a calculated liquid hydrogen fuel system and a turboelectric power transmission complete the aircraft design reducing the energy consumption, manufacturing effort and increasing the reliability and passenger safety.

    • Looks interesting. Great to see that a university is working seriously on something like this.

      I note that this concept is using hydrogen combustion in a gas turbine so as to generate electricity, which is then used to power electromotors...so these people are evidently comfortable having a combustion-based system in combination with hydrogen -- risky, but not impossible.

      I find that they're rather optimistic with regard to the availability and performance of HTCs (high-temperature superconductors)...but time will tell if/how that works out. HTCs are brittle and difficult to machine, so they're use in machinery has been problematic. But there may be a breakthrough around the corner.

      As a general note: even now, Airbus is considering counter-rotating, exposed-blade engines for next-generation aircraft, regardless of the fuel used. They have a larger noise footprint and are risky in terms of uncontained blade detachment, but they have much greater efficiency.

      The 2045 timeframe is consistent with the title in this article.

      • Here's a PhD thesis looking at LH2-powered aircraft with internal-combustion turbofan engines:

        The Potential of Liquid Hydrogen for long range aircraft propulsion

        https://core.ac.uk/download/pdf/139335.pdf

        2.3.2 Modifications to the turbofan design and performance tool (Page 32)

        Excerpt

        The thermodynamic changes by switching from kerosene to hydrogen are accounted for by importing the proper combustion gas properties data into the tool. This will not be reported here as it is described in Appendix C. Below the implications of the fuel switch on the amount of cooling air required to maintain the turbine metal temperature to a certain value are described first. A next subsection reports how the influence of the fuel injection temperature on the engine performance is taken into account. Finally the change in combustion chamber length is commented upon.

        -

        A.5 Impact on aircraft handling and safety (page 147)

        Excerpts

        In order for hydrogen to be a viable candidate aircraft fuel both the aircraft handling as well as safety of aircraft and airport need to be compliant with current levels. Minimum changes to current practices are preferable even though the distinct features of hydrogen make this very unlikely.

        Boeing (1976), Brewer(1976) and Sefain (2005) all show that LH2 aircraft can be handled exactly like conventional fueled aircraft. The aircraft can be fueled at the gate while housekeeping operations are performed, passengers board and cargo is loaded. Figure A.11 shows a typical aircraft servicing schedule for liquid hydrogen fueled aircraft. Turnaround times are furthermore likely to be the similar to kerosene fueled aircraft (Brewer, 1991). To minimize fueling times and boil-off losses, as well as fatigue due to thermal cycling of the tank, the hydrogen tanks should remain at cryogenic temperatures at all times. The tank temperature should be allowed to rise only when the aircraft is expected to be out of service for an extended period or if entering the tanks for inspection or maintenance is required. The tank must then first be de-fueled, subsequently purged with inert gas while carefully warming up the tank after which the inert gas is replaced with air. Refueling must on its turn be preceded with purging, replacing of the inert gas with gaseous hydrogen and a gradual chill-down before filling the tank with liquid hydrogen again. This is expected to take up to several hours, mainly depending on the size of the tank (Brewer (1991) and Sefain (2005)).

        Since the accident with the Hindenburg airship, it is commonly believed that hydrogen is a very dangerous fuel. Several safety studies, conducted for industry branches ranging from aircraft over cars to nuclear utilization of hydrogen have however shown that hydrogen provides excellent safety features due to its inherent properties and as such does not deserve its reputation. The common misbelief concerning hydrogen safety is thus a psychological rather than physical problem. Obviously each specific design must be made with the characteristics of hydrogen in mind from the start. Key issues in hydrogen safety are ensuring that hydrogen cannot accumulate in certain areas by proper venting and allocation of sensors to detect the presence of hydrogen. Below some features of hydrogen safety will be commented upon.The properties of hydrogen to which reference is made in this section are compiled in Table A.1.

        Since hydrogen is the smallest molecule it has a greater tendency to escape through small openings than any other liquid or gaseous fuel. Based on properties such as density, viscosity and diffusion coefficient in air, (subsonic) hydrogen leaks through holes or joints of low pressure fuel lines occur at a rate 1.3 to 2.8 times faster than a natural gas leak from the same size of hole (Barbir, 2005). As hydrogen has a very low energy density per unit volume, its leak will nonetheless result in a much smaller energy release than most other fuels (Barbir, 2005). If the leak would occur in a high pressure line on the other hand, the flow will be sonic at the hole and the higher speed of sound in hydrogen (1308 m/s (Barbir, 2005)) would lead to a much higher leak rate compared to other fuels. The lower energy density argument however also applies here leading to similar conclusions as for the laminar leak (Barbir, 2005).

        If a leak should occur for whatever reason, hydrogen will disperse more rapidly than any other fuel due to the combination of its high diffusivity in air and its buoyancy (Barbir (2005) and Faass (2001)). This is reflected by the danger zones from Figure A.12. The figure shows the danger zones for a 3.3 cubic meter liquid gas spill with 4 m/s wind. The hydrogen will evaporate in a very short time and rise and dissipate into the atmosphere so rapidly that the hazardous area remains very small (Brewer, 1991). If the spill would be ignited, as will be the case with most aircraft accidents for most fuels, the duration of the LH2 fire will be very short so that the fuselage will not be heated to the point of collapsing (Brewer (1991), Brewer et al. (1981), Faass (2001), A.D. Little (1982) and Witcofski (1981b)). For a 400 passenger aircraft, the fuel-fed burn would for instance only last for 15 s (Brewer, 1991). The low radiative heat transfer further aids in keeping the fuselage temperature low.

  • Synthetic hydrocarbon fuels or cryogenic hydrogen represent a much better solution for 3 reasons: 1 They can be made fairly efficiently (about 60% or better). 2 Despite the fact that batteries are more efficient an electric aircraft that might fly between Dublin and London will have a mass fraction of 55%, somewhat greater than an aircraft that could fly Sydney to London nor will that weight reduce during the flight. Electric aircraft will be 3 times larger for the same payload except in the case of very small distances and this reduces their efficiency. 3 The Generation of electrical energy requires storage and transport from a remote location, producing a synthetic chemical fuel provides for this. You can make fuel in a dessert with nothing more than water and air. The best batteries available, the kind used in Tesla Model 3 have a energy density of 248Watt Hours per KG and have a C3 (20 minutes) discharge capacity. Such batteries can not be used for aviation because they are not certified and batteries with less than 66% of the capacity must be used. Pilots have already died from inextinguishable lithium battery fires. They will be lethal. If you do some calculations you end up with an aircraft that might fly 150NM. with some hope of being economical. Hybridising the aircraft with essentially an oversized APU would increase this greatly as it would provide for the diversion, head wind and hold reserves as well as ease the load on the battery.

    Electric flight will have its place but it will replace taxis and cars in short flights in the form of eVTOL. An electrica aircraft with the performance of a sail plane could certainly do Dublin London but synthetic fuel is a better solution.

    There are batteries in the lab that will have twice the energy density and will rely on much safer technology. A trebling in battery performance will allow electric aircraft to conduct many flights of up to 500NM (eg London Dublin Paris etc)

    However synthetic fuels are better.

    • I presume that hydrogen combustion to thermally drive a turbo fan is a big no-no, because it's generally not a good idea to have combustion going on anywhere near a volume of hydrogen. Systems employing cryogenic hydrogen will be using it to generate electricity in fuel cells...agreed? Or do you still see a role for hydrogen combustion?

      • The first jet engine in the world (ran about 3-4 weeks before Whittle's), von Ohain's HeS 003A ran of hydrogen and its actually possible to design a lighter engine with it. There are however fuel handling issues. The proposals Ive seen are aircraft like the Dornier 328JET with a pair of large cryogenic fuel tanks outboard of the engines looking like drop tanks and an A300 with a single cryogenic tank along to top of the spine. Hydrogen rises up so its safer underneath it than above it. Building a system of cryogenic refuelling points at major Airports could be done and might be useful for certain kinds of flight. Issues with hydrogen are 1 it will be 3.3 times the volume (though 1/3rd the weight), extreme flammability means sophisticated refuelling equipment. Hydrogen will leak, cant be stopped, and will rise up to destroy ozone layer and be lost in space. I think the fire issues can be handled. Synthetic hydrocarbon made from CO2 captured from the atomopshere or ocean and then combined with hydrogen over catalysts has been around a long time. The US navy tested pilot plants (Northrop Grumann) to make aviation fuel aboard its aircraft carriers. They were 34% efficient. The ZSW in Germany did a miniature plant in 1990's that was 38.4% efficient but they rekoned they could do 60% efficiency. The efficiency of carbon dioxide capture is now so high efficiencies of 60% to 70% are guaranteed. Perfect for nuclear to solar or wind from remote parts of the world.

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