Bjorn’s Corner: Why e in ePlane shall stand for environment, Part 12. Battery risks.

March 6, 2020, ©. Leeham News: We use this week’s Corner to discuss the safety hazards a change to an Electric or Hybrid-Electric airliner introduces.

The trigger is two battery fires in six weeks for the electric aircraft prototypes which are now flooding the market.

Figure 1. Eviation’s Alice battery-driven prototype. Source: Eviation

Safty for electric aircraft

With each change of technology, there are unknown unknowns, and the hyped Electric aircraft market is learning this fast.

On the 22nd of January, the Eviation Alice prototype was damaged in a fire during ground testing, apparently with the fire starting in a ground-based battery system.

Last week, the Lilium Jet, Figure 2, was damaged in a battery fire during maintenance. The Lilium jet was damaged beyond repair whereas the Alice prototype faired better.

Figure 2. The Lilium Jet battery-driven air-taxi. Source: Lilium.

The events are not surprising. Batteries for Electric or Hybrid-Electric aircraft have to be very high capacity with energy contents of 10 to 100 times the Tesla cars’ battery packs.

The projected packs for the Alice and Lilium Jet are 920kWh and 1,000kWh respectively, whereas a typical Tesla pack holds 100kWh. A pack for a regional airliner would top 20.000kWh.

Anyone who has seen a Tesla car having a battery fire knows these fires as intense and cannot be stopped, a least not with normal means (Tesla cars seldom catch fire but when they do the fires can’t be stopped).

Car racing has the knowledge

It’s clear our 200 Electric or Hybrid-Electric projects do not have the knowledge needed to handle the risks involved with the needed high-performance battery packs.

The area that comes closes to batteries for electric or hybrid-electric aircraft is the batteries for Formula E car racing. These have to be light, have a high energy density, power capacity and stay safe in a crash.

Rolls-Royce uses battery technology and knowledge from Formula E for its speed record-attempting ACCEL electric aircraft, Figure 3.

Figure 3. Rolls-Royce ACCEL electric aircraft speed record aircraft. Source: Rolls-Royce.

There is quite a bit published around the Formula E battery systems and the knowledge the series has gained during the five years it has run.

Here the key points:

  • High power battery systems are dangerous. If they start a thermal runaway, they self feed the process with heat and oxygen. You can only put out the fire by soaking the battery with huge amounts of water, so it cools the process to the level where it stops due to lack of heat.
  • You trade energy density (kWh/kg), power discharge capacity (kW) and safety. The cells heat up during charging and discharging. You need a cooling system to keep the cells at less than 60C°. Higher temperatures and you risk a thermal runaway.
  • To keep the cells under control, you need to monitor temperature and electric data for each cell. A Tesla size battery has 10,000 cells, so a 10 to 100 times larger battery system has quite some controlling gear that shall work at all times.
  • The battery containment must be able to contain a battery fire from these cells; otherwise, the battery system will destroy the aircraft’s aluminum or carbon fiber structure, which in the air means a crash.
  • The Formula E races run with carefully designed safety rules and precautions. Mechanics, drivers, and marshals are trained on what to do with unsafe battery systems and there are accident/fire fighting squads spaced around the circuit.
  • The energy density of these racing batteries is around 0.12 to 0.17 kWh per kg. This is when the battery systems operate at ambient air pressures. What happens at 35,000ft is not known (today’s airliner batteries are inside the pressure vessel). The Alice battery is specified at 0.25 kWh/kg.

We can see there is expertise in the market that can help the 200 UAM/Electric aircraft projects of today. But we also see what risks the technology entails, especially as entrepreneurs start pushing the trades listed above to get their specs to work.

I don’t think the air transport system has any idea on the risk level involved in Electric and Hybrid-Electric aircraft and the trip we have before us to bring the technology to a mature state.

I know Siemens woke up to the risks and decided Rolls-Royce was a better home for its electric aircraft project. Engine OEMs are used to and can manage high-risk developments (the gas turbine had far from a smooth development journey).

Once the accidents start happening, a broader audience will wake up to the risks with the technology and the craze around electric UAMs and aircraft will settle. It has already started.

56 Comments on “Bjorn’s Corner: Why e in ePlane shall stand for environment, Part 12. Battery risks.

  1. The high risk also mean well known aerospace names will keep a distance as the damage to their brand can be immense ,when not if, major disasters occur.
    In spite of Bjorn’s warnings I can see the glass is always full crowd commenting here with their hopes and dreams as if they real and ignoring the real problems.

    • I have yet to see an mfg fail to explore and offer the edge of tech.

      As its the responsibility of the aircraft mfg and the agencies to say yea or nay and come up with proper testing (which was not done on the 787 battery) its not going to be an mfg issue.

      Collins wrote the MAX program and has pretty well escaped any scrutiny for it (sans where it was written).

      My beloved engine mfgs are vested in the field. Its not that they think its going to take over but they feel its a future technology they need to have expertise in.

      One that crosses over is RR as its a rare piston engine and jet engine mfg combo. Virtually all diesel mfgs are construction/farm/ vehicle mfgs with few stand alone like Cummins Engine.

      GE has engine interests but not sure where they are at these days. The engine division was deeply invested in locomotive which has applications in battery that works

      Not all solutions are battery so the others have different takes

      • GE Transportation has been sold to Westinghouse AirBrake or as its known, Wabtec

      • The Collins system, I have read, was based on an 80286 16 bit CPU. This CPU originated in 1982. It has issues with computing power and multitasking. It’s said that that this is why the system alternates use between left and right alpha sensors that was in the failure chain of both crashes.

        Two years later in 1984 intel introduced the 80386. Windows 3.0 came out in 1990, Windows 3.11 came out in 1992. the first proper multitasking operating system Windows NT 3.1 for server and latter workstation came out in 1993. NT was developed by DEC and unlike Win 3.11 and Win 95 was truly multitasking. In 1997 the B737NG was introduced on the NG using the 80286 probably from the previous generation. A320 aircraft have 3 different CPU written by 3 different teams.

        Part of the reason its taking so long is that the CPU in the MAX are not adequate and the original programmers are well into retirement. Its amazingly stupid. Id say regulators are pissed about a few other things such as the uncontained engine failure that killed that lady on a southwest flight and cable routing issues that got worse not better in the MAX.

        • William, this all has been debunked. There is no issue with computing power or adequacy in the MAX. If that were true the aircraft could never be certified.

          Nor was that the cause of using right or left vane for MCAS, that was a design decision based on the risk assessment of the original small-effect MCAS programming.

          Nor is it necessary to bring programmers out of retirement to work on the MAX or an older CPU. The software has been continuously updated throughout the life of the 737. That’s how the the AoA disagree indicator bug got introduced, as well as the MCAS programming.

          The delay was caused by being forced to rewrite the entire FCC code, instead of just the MCAS portion, due to changes in the stringency of cosmic ray testing that were made after the MCAS fix.

          That was a huge task that didn’t really have anything to do with the accidents. But it was possible to force an un-commanded stabilizer runaway in the computer control circuits, and that was an MCAS-like behavior, and pilots did not recover well from it. Boeing could not show that it could never happen, even though extraordinarily unlikely. So the FCC code had to be re-written in order to detect an internal error.

          It’s common for flight control architectures in a given aircraft to not change unless there is a compelling reason, because of the enormous number of safe hours that have been accumulated under the original design. That is the main factor in retaining the 80286.

          • That doesn’t sound 100% right. Modern CPU, modern operating systems, computer languages, compilers and debugging environments provide many facilities for assisting the programmer in avoiding errors and simplifying his task. Multithreading and multitasking, strong ‘typing’ of variables, compiler warnings. Also modern fault tolerant systems concepts provide seamless ways that two processors can operate in a redundant and fault tolerant way with a hot swap over. Some kind of duel boot issue was one thing that held Boeing’s rewrite up. The point I’m making is that by sticking to an older architecture Boeing made their job harder. No duplicated architecture is really well suited for a high availability system that operates a primary flight control surface FBW which MCAS had turned the stabiliser into done. It kind of enforced ‘wrong think’ anyway. The duplicated architecture as opposed to triplicated architecture kind of reinforced wrong thinking.

          • William, these are matters of established fact, whether they “sound” right or not.

            The software development takes place on modern platforms, with all the tools you mentioned. Only the compiler targets the 80286 instruction set. It could target any processor for which it knows the assembly language.

            The original 737 FCC configuration was hot fail-over from the beginning. Now it is a dual concurrent system with internal fault checking.

            The triple system is needed when the computers have full authority, as they must make control decisions. When that is not the case, a dual system is well suited.

            The MCAS system is not FBW. Pilots have had the ability to override or disconnect, from the beginning, as shown on JT043.

            The boot issue you referenced was a hardware initialization issue when loading the software into an actual aircraft. It was a Built-In Test (BIT) error. It wasn’t a dual-boot issue.

  2. If you doubt the danger of batteries, look up UPS Flight 6 and see what happened to a new 747-400. They don’t just produce heat but also a great deal of smoke and hydrogen fluoride which is extremely toxic. There’s a very sobering animation on U-Tube.

  3. All new Technology has to go thru “The bleeding edge”. Early jet fighter Engines had poor life expectancy and the military poured Money into them to solve problem after problem. Similar will happen with electrical Aircraft battery systems but today with the softwares and computers available it should go more precise and quicker.

    • These risks are known from other industries but are clearly multiplied 1000 fold in aviation so additional contingencies must be provided for. There are promising future laboratory chemistries that promise to eliminate most of these risks. In the meantime there may be other more immediate ways forward for promising projects such as Lilium: Each individual cell could have sensors embedded that detect a thermal run away. The cells would be organised into multiple fire walled batteries. If a problem is developing in a battery it can be rapidly isolated and doused with a coolant or ideally removed from service. I think this can be done without significant weight increases. It may not be possible to continue the flight but the aircraft could survive the 5-10 minutes required for an safe emergency landing or deployment of the ballistics parachute.

      I note that 3000 volts DC creates its own hazards. Direct current is not easy to switch of or break an arc that had formed.

      The industry should focus on phasing in a percentage of carbon neutral fuels. So called E-fuels especially the PtL “Power to liquids” type that make synthetic jet fuels out of hydrogen and CO2. Third generation biofuels that can ferment cellulosic material from waste wood or crop stalks or genetically altered sugar beats or fuel that is certified to have sequestered a proportionate amount of CO2 underground in old oil wells. A 0.33% PtL fuel per flight might initially add 1% to fuel costs but would commence the industrialisation and commercialisation of such fuels. Hydrogen is a way off.

      • EASA and FAA certification regulations for batteries and their charging and cooling system are important. There migh develop into system to jettison ignited battery cells out of the aircraft burning up before hitting the ground, like flares on fighter aircrafts. Once the regulations are firmed modern engineering tools can do a good job predicting its performance.

        • They arent going jettison ignited battery cells…its too silly for words and would never be accepted by the certification bodies. Clearly you have no idea of the practical issues to even do that and its unrelated to ‘designed to burn’ military flares – which only ignite after leaving the aircraft- important- and are individually quite small.
          Anyway these two ‘prototypes’ dont seem to have taxied yet before catching fire and their biggest problem is yet to come , the crash and burn of the financial kind.

          • Future will tell who laughs at the end. The present 787 battery box venting system discharges an interesting mix when battery cells burn. (with no restriction on altitude).

          • Tech start up projects often “catch fire”, even ones that appear to be non flammable.

          • The full scale Lilium Jet has been flying for 6 months and conducted transition from vertical to horizontal, you can see their video here:
            Fortunately the second prototype is almost ready so apart from the time to complete the investigation little time will be likely be lost. Note this was a ground accident suggesting an experiment or ground accident that went wrong. Lilium’s flight test campaign is 5 years, they are only at the beginning, so they are being extremely through as well as going for full EASA certification. Eviation’s Alice was also a ground accident.

            Eviation is also preparing an aluminium air battery propulsion system, apart from organic lithium, as a higher performance backup. These are currently capable of 1300Wh.Hr/Kg, about 5 times LiPo. So alternative way forward is zink air, nickel air or vanadium style redox batteries that keep the electrode and electrolytes separate. “Refuelling” an electric aircraft one day may involve changing out a Aluminium Air Battery Pack the size of one or two LD3-45 unit load devices. Technology is not settled.

            The situation with thermal runaway LIB “Lithium Ion Battery” prevention is actually quite optimistic. There are a number of methods. CID “Current Interruption Devices” such as PTC thermistors are effective. Alkanes (iso-octane is one but perdecane is the best) or Amines are effective TRR “Thermal Runaway Retardants” and cells which loose a trivial 4% in capacity with a pouch are resistant to venting and heat rise caused by mechanical damage such as crushing and being punctured by a nail. There are thermally activated layers that can release of TRR. The literature is replete with methods, many already in use often in smaller cells. Obviously integrated circuits with temperature and pressure sensors can be embeded in each cell to condition monitor the cells and initiate appropriate action.

            The big hammer is cryogenic freezing or circulating saline through the battery pack to take away the heat. cryogenic freezing completely passivates the battery and is a way we will likely to see suspect batteries stored, transported. If there are 36 batteries on an aircraft made of cylindrical cell the voids between cells in a battery will be about 25% of 2.8 ie 0.7% and twice this amount of saline or a cryogenic liquid can reasonably be carried to freeze or cool the battery maybe with a circulation or saline. It seems the various safety systems of flight rated batteries will probably mean they will always be 10-15% less than automotive.

            I strongly believe we are a long way from climate crisis, 1000ppm CO2 may be good, but I’m in favour of prudence and fascinated by the liberation it may bring from certain cartels, so long as the money power or their useful idiots, the lunar left, do not use this useful crisis to enslave us.

            Elon Musk’s Space-X and its fly back boosters has humiliated Lockheed Martin, Boeing. His Tesla giga factory in Berlin is about to decimate many of the big German car makers who despite 45 years of electric, fuel cells, liquid hydrogen IC and cryogenic hydrogen experiments and small production runs vehicles are scrambling with their pants down. I would take this man quite seriously.

            I personally believe PtL fuels will be the future. (ideal would be if it were produced by nuclear thermochemical processes, which would make it economical and cheap) but the electric flight with 400-700 Watt.Hour batteries on the horizon may happen in 10 years.

            Sumitomo has developed superconducting Truck and Automobile electric motors. Although big industrial electric motors are 99% efficient our EV motors are only 90%. The cooling systems are apparently quite small and allow a cryogenic motor to operate a 100%.

            There are some interesting youtube videos of stable flames being sustained by powdered metals. We may see an aircraft powered by and emulsion of powdered aluminium powering a closed cycle bryaton engine whose exhaust of aluminium oxide is captured.

            Interesting times.

  4. Bjorn, could you expand on the line “I know Siemens woke up to the risks and decided Rolls-Royce was a better home for its electric aircraft project.” a little please?

    Was it that RR had greater knowledge in general, or greater knowledge specifically aviation related, or something else?

    The learning process globally in transportation is also skewed by the battery technologies that government policies may favour in road vehicles, such as China’s policy of rewarding in relation both to vehicle range and battery energy density that currently favours NCM batteries. I don’t know how holistic the Chinese policy is (eg is it entirely driven by auto or is it done with an eye to aero too?) or what the overall policy pressures are in battery development but it would be good to know as this could affect ePlane timelines by years.

  5. Rolls-Royce has been in aircraft engines and systems for over 100 years (first engine during WW I), Siemens has no such experience. Siemens became aware of the risks involved and decided that an aeronautical company such as Rolls-Royce was better suited to develop the technology.

      • Indeed, Siemens-Halske became BRAMO (Brandenburg motor) which was merged into BMW. The companies innovations and achievements are illustrious. The Siemens-Halske Sh.III rotary had the propellor counter rotating to the engine at half speed eliminating the nasty gyroscopic precession known in rotaries of WW1, they developed the first drop tank for the Siemens-Schuckert D.VI and even the BMW 003 jet is an project of the original BRAMO Siemens Schukert team. They developed their own radial engines but in 1919 allied commission prevented engines greater than 100hp. BMW and Rolls Royce had a very successful cooperation with the BR 710/715 used on the B717 which had an superb reputation on reliability, cost and ease of maintainability. Anglo-German cooperation has been an quiet core of European Aviation. RR are cooperating with Liebherr on ultra fan (I know they’re Swiss)

        • Was not the BMW-Bramo team taken to Ukraine to develop the Tu-95 Bear bomber engine from a bmw turoprop. When done they could travel home to Spandau

          • The BMW work is associated with transfer to France via Dr Hermann Oesterich where they did influenced the ATAR of the Mirage series. German and French Engineers had been working together under these exceptional wartime circumstances and there was a kind of grudging respect. Oestereich wanted to go to France, not the USA. The Junkers team was largely in Eastern Germany and therefore in the Soviet Sector. They did go on to influence the NK-12 strongly, they were rolled from one design team to another. The NK12 clearly follows the architecture of the Jumo 022 and BMW 028 (single spool turboprops, with axial compressors, blow out valves, planetary gear boxes). Ferdinand Brandener who had done or lead much of he NK12 work came out of “Soviet Captivity” and proceeded to work on the E300 developed for the Ha 300 supersonic interceptor that Messerschmitt/Heinkel was developing for Spain and then Egypt. A credible design that was up to the MiG 21, Mirage, Phantom of its day but did not have the luck of a steadfast funding. Quite a few engineers ended up in the UK such as Dietmar Kuchmann who became British citizens and received Royal Honours and of course many went to the USA such as Franz Anselem (Jumo 004 leader) who went on to head the Lycoming division set up to develop gas turbines for helicopters (for which they were suited and revolutionary) leading to the T53 helicopter engine of the Huey which also lead to the AGT1500 of the M1 Abrams. He has a biography called “my career from jet engines to tanks”. Much of Germany’s prewar industrial capability was based in Eastern Germany. Being based in the communist soviet sector and being a small country it eventually destroyed many of these industries such as Auto Union and Junkers. Nevertheless Junkers engineers produced the Baade 152 jet airliner in 1958 and the Pirna 014 turbojet so this little country was punching up there with the Comet 4 and B707 for a while.

        • RR bought out the BMW side of the aero engine business 15 years ago

          The FG story is incorrect about Motorenfabrik Oberursel being a predecessor to the original BMW engine line. It was a
          WW1 manufacturer in its own right and later became part of Klöckner-Humboldt-Deutz, mainly license production, and in the 1990s was the part of the RR-BMW tieup ( Maybe the Quandts had shares in KHD).

    • I see RR’s desirable competence as more engine certification centric than engineered benign risk management centric ( though “how to mitigate high energy defects” is in tier one of desired competence.

      Siemens&Halske used to do aero engines and a plethora of other large industrial installation to consumer ranged products. One of the first everything corporations.

      Siemens&Halske aero engines were separated from the main concern, renamed BRAMO and then ingested into BMW. All between WWI and WWII

      Now for a fun fact: some of the BMW sites in Germany are now RR owned.

    • Realistically …
      There’s not going to be a battery with fuel-like energy-density , any time soon . The real question is : Will there be special applications , better served by hybrid architectures ?
      Another such question is : Is large-scale production of synfuels from waste-carbon , using “Green” energy , practical near-future ?
      *Fuel-for-thought !

  6. Dear Bjorn,

    Hydrocarbon fuels had been around for more than 100 years, then TWA800 happened, a widebody airliner exploded in the sky, killing 230 people.

    Of course there are inherent dangers whenever a large amount of energy is stored within a small space. And yes, there are unknown unknowns, certainly. But the NTSB spent tremendous resouces investigating the accident and produced an extensive report, with recommendations on how to implement changes so that the energy is stored more safely going forward.

    The existence of dangers doesn’t, in my opinion, necessarily imply that we must categorically reject technological advancements of every kind, and be pessimistic about the future.

    Also, I think it would be a huge mistake to jump to the conclusion that, because TWA800 happened, all employees of Boeing, Pratt & Whitney, contractors, regulators, and other parties, are somehow incompetent or devoid of knowledge as to the inherent dangers of energy storage. I believe they are generally very well aware of the inherent dangers and are doing their very best to manage them.

    I love your work, Bjorn, but I believe this piece was a little bit unbalanced. But thank you for putting your opinions out there, I love reading them and the conversation is important.

    • A fuel explosion requires fuel vapor, oxygen, and a source of ignition. Prior to TWA 800, the industry argued that suppressing the source of ignition was enough to prevent an explosion, but it finally happened anyway. After TWA 800, the focus expanded to also controlling the flammability limits so as to eliminate two of the three requirements instead of just one.

      I think Bjorn’s point is that for existing high-density batteries, you can only control the temperature, which is analogous to suppressing the source of ignition. And you can only do so marginally, as the many battery fires bear witness. But you cannot control the other components needed for the runaway reaction, as they are embedded in the battery. You can inert the surrounding space to suppress fire outside the battery, but can’t stop the energy release once it begins. So you basically have a long-duration explosion, the uncontrolled energy is released over minutes instead of instantaneously, but in flight this wouldn’t make much difference.

      Newer technologies or research may change this, but for now its unlikely that the higher-density batteries would be flight-certified, for safety reasons.

  7. The battery pack could be jettisonable. Not cool for the people below though.

    • It burns pretty quick, there might be a zone in altitude after laving the runway when it should not be jettisoned but a separate cell or cells jettisoned should be able to burn out from a certian altitude before hitting ground.

    • Its kind of funny and would good in a novel but I think it actually makes sense. Imagine if you have 1 battery fire 10 per million flights, maybe about the same as an uncontained turbine failure. The aircraft is a pilotless passenger eSTOL flying between Paris and the City of London. The batteries are in jetisonable modules suspended a little distance from the aircraft. An artificial intelligence on the eSTOL detects a ‘battery venting with disassembly’ that can not be contained. It will then determine if the batteries can be ditched over the English Chanel or the French or British countryside by consulting GPS mapping data, shore based radar aware of boasts and ships and an artificial vision camera. The future air traffic management systems for pilotless aircraft will probably have to have continuously calculated crash zones for when all else fails and make decisions like that anyway. In 90% of times it will be safe to drop. I know no few will accept it but it should be work. The key is taking the decision away from a human into the hands of AI. Much better to develop as safer battery systems though.

      • Depending on battery cell size it will burn out to ashes within a defined time rushing thru the air after jettison.
        You have cases with jet engines having compressor/turbine failures producing “corn combs” with almost all blades broken off one rotor and exit thru the engine exhaust and they hit the ground as they leave the engine (as Norwegian 787 over Rome).
        These Lithium-Nickel+other alloys can produce dendrites growing like needles from small “FOD” and once the largest one causes a short circuit. So there might be requirements for periodic NDT of each cell determing size of found dendrites just like NDT requirements on engine disks/spools and rotating air seals for cracks in addition.

  8. One thing most people overlook is this: not only hydrocarbons are extremely energy dense; they are just half of the stuff necessary for combustion. The other half is the oxygen in the air, which you do not need to carry around.

    All of those touted batteries “solutions” have both the “fuel” and the “oxidant”. This in itself is a heavy weight penalty, even if you forget the electrolyte, packaging etc.

    I suppose that if you have electricity and want to run an airplane, the best you can do is to synthetize a hydrocarbon or similar liquid fuel on land and burn it in a regular gas turbine. The US Navy is researching that for purely logistical reasons using salt water and air in aircraft carriers. On land, this could be even easier due to the wider availability of raw materials.

    Of course, you can *easily* run a gas turbine on vegetable oils and skip all this synthetization nonsense.

    All this hype on electric airplanes makes no sense at all.

  9. Realistically …
    There’s not going to be a battery with fuel-like energy-density , any time soon . The real question is : Will there be special applications , better served by hybrid architectures ?
    Another such question is : Is large-scale production of synfuels from waste-carbon , using “Green” energy , practical near-future ?
    *Fuel-for-thought !

    • There is nearly 90 years of successful industrial scale experience in the use of large electrolysis mainly for production of nitrate fertiliser using hydro power in Norway, Canada and Egypt but also small scale for companies that need a cheap in site supply of hydrogen for chemical processes, welding. We have now high temperature electrolysis that is 80-85% efficient as opposed to 60%. There is as much experience in the fischer-tropsch reactions which make synthetic gasoline, jet fuel, diesel initially using coal and recently using natural gas or petroleum gas. Very well developed. Capturing concentrated CO2 is also not a problem. Capturing dilute atmospheric CO2 can be done with reasonable efficiency. There are two processes in semi commercial use. One is capturing in Sodium Hydroxide absorption towers and releasing the CO2 while regenerating the Sodium Carbonate back into Sodium Hydroxide solution. There are variations of this. This seems to require about 1KW.Hr per KG of CO2. Then there is absorption onto amine plastics which must be heated using low grade heat (2.5kW.Hr per Kg of CO2) but its low grade 90C heat easily obtained from water nuclear, solar thermal or the fischer tropsch reactions which are exothermic.

      The real issue is power costs. Hook up a Vestas V90 (peak power 2.5MW which will produce 1MW average power (24MW.Hr/day) you will be able to produce about 1500L/fuel per day maybe 2000L using advanced tech. However when the wind doesn’t blow (mainly at night) your electrolysers and reactors will be unused much of the time. Cost of fuel will be about 1.60 Euro/Litre. (this is with insanely expensive European wind power, seems to be most expensive in the world)

      Hook it up to nuclear an the economics look good. Waste heat can regenerate the amine CO2 absorbers and even a relatively low temperature reactor can preheat the steam needed for high temperature electrolysis. Introduce thermochemical water splitting and the economics are very cheap.

      Its no surprise Bill Gates is supporting carbon engineering and its synthetic jet fuel effort and at the same time nuclear reactors that can destroy their own waste material. I recall his comment that the idea of powering Tokyo with renewable energy was ridiculous.

  10. for the record, as of today there have been 19 car fires involving Teslas since 2013 worldwide. 19 total, world wide, in 8 years.

    10 were accident related where the accidents were severe enough to puncture the battery compartment
    5 were related to charging, some due to faults at the charger
    the other 4 are of unknown cause.

    there are 171,500 vehicle fires in the US alone on an annual basis. 8% of all fires responded to in the US are car fires. (source:

    to suggest that electric vehicles are somehow more vulnerable to fire is absurd.

    • I didn’t. I said when they burn you can’t stop it. This means a possible airline crash when it happens, killing all in the aircraft.

      Air transport is now at a level of almost total flight safety from aircraft-related problems. The tolerance level is nil. The MAX drama shows this. The MAX problem took down two aircraft out of 22,000 flying every day with a spacing of six months in between. One such fire and that aircraft line is dead. The public will not fly on the aircraft type.

      The MAX problem is minuscule compared to the above risks and consequences. But the Electro proponents refuse to understand the scale of the safety issues. What is acceptable for ground transport is not for air transport.

      • Bjorn, you can’t stop an inflight fire from just about any source.

        easy examples are TWA-800 (blew up explosively in mid-air), the Swissair DC-10/MD-11 (insulation fire sparked by chafed wiring), the DC-9 with the oxygen generator bottles (which, while nobody carries them as cargo on passenger flights anymore, there are some on every aircraft and a maintenance error could result in catastrophe)

        this needs to be looked at with objective statistical measures, not 1 in a billion worst cases. there are plenty of potential risk mitigation strategies out there, ranging from the dumb and simple (the 787 solutions) to more sophisticated solutions such as podded batteries that can be dropped like a drop tank.

        • I think the issue comes down to the required mitigation measures. We don’t have any internal measures for the battery at present. We only have external measures, and as Bjorn pointed out, those don’t stop the release of energy, only try to prevent it from being catastrophic, which becomes progressively more difficult as the energy level increases.

          From the viewpoint of aircraft safety, saying you can’t stop the release of energy but will try to contain it, would never be acceptable.

          With the MAX, we know the pilots could have contained the MCAS failure, but some were not able to, which has now been conclusively shown by pilot testing. So effectively the malfunction cannot be allowed at all, hence the MAX remains grounded as many other potential sources are examined and addressed.

          Similarly in the nuclear industry, release of radiation cannot be allowed at all, so the focus of Gen-4 is on internal measures (walk-away passive safety), which still may not be enough in the public eye. External measures are not deemed sufficient, even though the probability of failure is very low.

          Internal limiting measures to prevent battery malfunction may become possible in future, which would change the safety analysis from catastrophic failure to loss of power and propulsion.

          • We do have internal measures developing, TRR “Thermal Run away Retardants” which are effective in limiting release in case of mechanical damage (crushing of cells, penetration by a nail (which boys will do) at a cost of 4-5%. There seem to be thermally activated mechanisms capable of releasing these or similar chemicals. Replacing cobalt with tantalum dramatically reduces Thermal Runaway. The situation is not hopeless. If a 1kg battery capable of a 420WHr/Kg releases its heat at 100 times the normal rate (40 seconds) a flow of saline water at 10L/minute (the same as a European shower). Will carry away that heat with less than 60C temperature rise and prevent other cells conducting into run away. Cells can be equipped with vents that release pressure without bursting the cell and batteries as well. Other measures include internal microchannel filled with an eutectic that will conduct heat out to prevent the runaway.

            Gen IV reactors? Are we ever going to see them? They are essential for the and affordable ‘hydrogen economy’ and PtL because of their ability to provide consistent affordable power and ultimately to provide thermochemical water splitting. The lack of these reactors should be a talking point in climate catastrophist circles.

      • US Cars = 272 million (
        Car fires =171,500 per annum (
        Burn rate = 0.06% (per annum)
        Tesla cars = 297,300 (average over 6 years: 2013-2019)
        Telsa fires = 19 (2013-2019)
        Burn rate = 0.001% (approx 1/60th of rate of liquid fuel cars)

        Tesla cars are designed in an environment of zero tolerance to fires, the public is tolerant to fires in liquid fuel cars. There is no question that a liquid fuel vehicle could be built to be safer, just look at aircraft.

        Aircraft in the US = 213,000
        Burn rate 0.001%
        Potential fires per annum = 2.13 per annum.

        As Bjorn says, tolerance for accidents involving new technology is very low. Short haul might be different using drone type tech (redundant rotors). Batteries & electric motors have a long way to go to match aero gas turbine engines that have been continuously developed for more than 60 years for commercial air-transport.

    • “as of today there have been 19 car fires involving Teslas since 2013 worldwide. 19 total, world wide, in 8 years.”

      I tend not to believe those numbers. Can you show a ~ independent source. We loaded with half truths these days..

  11. These aircraft used NMC-type Li-ion batteries. Future battery chemistries may be less prone to thermal runaway, like current LFP-type Li-ion batteries (which have lower specific energy). Agreed with Rob^ that today’s higher specific energy batteries are unlikely to be flight-certified.

    Bjorn, small correction: power discharge capacity is just kW (not kW/s)

  12. there are about 272 million cars in the US, about 800k of those are Teslas.

    .8 over 272 = ~.003 (rounded up)
    .003 * 171,500 = 514

    so, if Teslas burned at the same rate as Gas cars, then there ought to be 514 Tesla fires a year…

    again, there have been 19 in 8 years. doing the math, Teslas are roughly 200 times less likely to catch fire than a Gas car. seems like a pretty good record to me.

    • You have to compare like with like …. cars under 3 yrs old that catch fire.
      And to make sure it excludes fires that occur after an accident

      The vast numbers of older and poorly maintained cars doesnt provide a comparable cohort.

      • Of course you are right that they should be compared to other luxury cars of similar age. All of the Tesla’s are exceptionally safe cars. Crash tests show Teslas beat every other luxury car manufacturer. Tesla models are at present the 3 safest cars in the USA. If there is an accident they also have the lowest probability of any injury to a person in the car. They’re 6 times less likely to be involved in an accident than average. Tesla are leveraging this with their own insurance:
        At 3.15 in to this video the impressive safety statistics are given:

        In 5 years, 2025, LIB batteries are expected to drop 70% in price.
        Bloomberg predict that the 1.1 million electric vehicles around the globe today will rise to 11 million by 2025, then surge to 30 million by 2030 as they become cheaper to make than cars with internal combustion engines.

        I suspect there will still be a substantial component of advanced pluggable hybrid cars that leverage carbon neutral fuel manufactured in remote regions rich in sunlight. (EG thermochemically in sunny dessert regions)

  13. EASA and FAA certification regulations for batteries and their charging and cooling system are important. There migh develop into system to jettison ignited battery cells out of the aircraft burning up before hitting the ground, like flares on fighter aircrafts. Once the regulations are firmed modern engineering tools can do a good job predicting its performance.

  14. Apropos that Eviation thingy:
    How do they actually expect to handle a ( one sided ) wing engine out condition?
    At the wingtip that propulsor has fantastic leverage!

  15. Whilst it is a laudable aim to eradicate the use of fossil fuels, I don’t really believe that it is realistic to contemplate doing so, therefore the aim should really be to reserve its use to the applications where it is most suited (e.g. aviation) and minimise emissions. We can’t consider aviation in isolation but other transport industries such as road and rail are better suited to moving to electric power, and a return to computer controlled sail power (or at least sail powered assistance). A far bigger problem will be that of heating domestic and industrial premises, power-hungry practices that we’ll study to replace.

    Once CO2 emissions are reduced to a sustainable level and we stop cutting down or poisoning the rainforests and oceans the planet will start to take care of itself as homeostasis reestablishes.

    There will always be a requirement for virgin plastics, and for the most part those will be made from oil but there are now developing technologies for recycling waste plastic back to biofuel, so there should be no excuse in future for waste plastic going to landfill and it is quite possible that widespread adoption of this technology could supply most of the aviation fuel needed. If it doesn’t, other biofuels derived from algal growth may help to fill the gap.

    • Oil, coal and natural gas is made from biomass like algea and aged quite a bit. Doing it quicker using biomass will come more and more, enforcing global tree plantation and algea growing in desert ponds can make most countries net carbon emissions negative. Just stopping coal mining and burning and use fuel with hydrogen atoms in it like natural gas will help and produce more rain.

    • “There will always be a requirement for virgin plastics, ..”

      Fossils are easy, cheap.
      But you can synthesize any hydrocarbon from elements
      and or molecules.
      Question of available (cheap) energy.

  16. Tail dragging, abandoned in the 1940s
    Butterfly tailplane, 1930
    Pusher prop, 1903
    Wingtip props, 1930s

  17. Tail dragging, abandoned in the 1940s
    Wingtip props, 1930s
    Pusher props, 1903
    Butterfly tailplane, 1930

    • What would you like to tell us here?

      Such arrangements come and go, return …
      so much in the decision process is based
      on prerequisites changing.

      • Nothing really, just an observation.
        Bjorn has already made the point that if some of these features were such a good idea they would be in use on non electric planes.
        Of course, some new technologies can make old ideas workable,like flying wings and fly by wire. Hydrofoils on sailing boats are a surprisingly old idea, Alexander Bell was playing around with them, carbon fibre has made them viable.

  18. Whilst runaway fires in batteries is a genuine problem,the elephant in the room is the terrible,terrible energy density ( and weight).Matters less when you don’t have to fight the gravity well but a total non starter when you do.Could talk about many other shortcomings ( cost for instance) but energy density is enough in itself.
    Yes ‘metal/air’ batteries offer a potential part solution but they really are at a theoretical laboratory stage .
    As stated above green fuels such as green hydrogen can be created if you have enough spare and cheap green energy to make it on an economic scale ( we don’t).If we did it would be possible to turn to Ammonia whether it be trains,planes,ships or automobiles -or indeed consumer heating.into a global clean fuel ( that is easily transported and stored-hydrogen isn’t).But this would require a globally organised shift involving every country -and a lorra Lorra money -can’t see that happening!
    So I agree with Roger.
    Hydrocarbons have lots of uses,some more important and irreplaceable than others.
    Global air transport is vital to our world economy.Its total CO2 output is trivial to many other carbon emitting industries.
    It’s critical that the industry is seen to be doing its utmost to minimise CO2 output if it wants to keep the doomsayers away.
    In many ways I think the industry is if only because fuel is such a large fraction of costs.

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