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  • Deeps thoughts about electric airliners

    With electric-powered airliners possibly appearing on the distant horizon, I got to thinking... Safety dictates that you would need to depart with enough battery charge to meet the same requirements that apply to fuel orders... ramp battery, taxi battery, trip battery, contigency battery, battery to alternate, holding battery, etc. But there are important differences. For one thing, the 'fuel' weight is fixed and constant, so it doesn't factor in determining available payload or optimal flight level changes. Since the weight is constant, the 'burn' is constant. But what about redundancy? I assume these designs will have multiple batteries with multiple cells. If you lose a cell or entire battery mid-flight, that has to be fail-operational, so you would need additional battery units as backups that are not included in the 'fuel' order. Perhaps you could retain the APU with a generator for emergencies, but then you would need to provide a fuel tank for that and would probably never use it. A RAT certainly isn't going to be able to power an 'engine' motor. Also, don't rechargeable batteries lose their efficiency as temperatures drop? Will deviation from standard temps be needed to calculate the 'trip fuel'? Will OAT determine optimal flight level for a given range? Or could the battery racks be highly modular in a way that the number of cells (and thus weight) installed on a given flight can vary by the 'fuel' order? Then we are back to 'fuel' weight vs payload and flight level decisions...

  • #2
    from a lay perspective, i certainly hope these things dont come online during my lifetime. the best minds cant even get electric cars right now, so why even dream of electrifying a commercial aircraft. get the tech right with cars, where the worst thing that happens is a couple of people die when the battery bursts into flames, as opposed to 100's.

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    • #3
      Oh Dear Christ!

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      • #4
        Originally posted by ATLcrew View Post
        Oh Dear Christ!

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        • #5
          Do you remember the title of my last thread? !!

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          • #6
            Originally posted by TeeVee View Post
            from a lay perspective, i certainly hope these things dont come online during my lifetime. the best minds cant even get electric cars right now, so why even dream of electrifying a commercial aircraft. get the tech right with cars, where the worst thing that happens is a couple of people die when the battery bursts into flames, as opposed to 100's.
            Apparently, well-made, undamaged batteries do not burst into flames any more than well-made, undamaged fuel tanks do.

            Airbus is exploring the hybrid route now with their E-Fan X research aircraft. This is testing a 2700hp electric motor in the #3 position of a BAe 146, with electric generation powered by an AE2100 turboshaft similar to the ones used on the C130J. Obviously, getting 2700 electric hp from a 4600hp turboshaft isn't what you could call efficiency but the point of this endeavor is to develop technology, not efficiency. However, they also install a 4400lb battery providing 2MW which equates to the same 2,700hp. The trick is to lose the hybrid aspect, the turboshaft. I suspect the work being done now anticipates further breakthroughs in battery and motor tech that will one day result in a battery 'fuel weight' needed to match turbofan ranges. There are other challenges, such as thermal issues (cryogenics may play a role) and high altitude corona effects (pressurization may be needed) and a lot of electromagnetic shielding. Will it ever be practical to pump 15MW of power into a wide-body, long-haul airliner...?

            In the nearer term, hybrids powered by two electric fans and two turbofans could allow descent phases to be flown on electric alone, although I would expect the turbofans to be left at flight-idle anyway in case a go-around or emergency ascent is needed. So I'm not really seeing the payoff there.

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            • #7
              Originally posted by TeeVee View Post
              from a lay perspective, i certainly hope these things dont come online during my lifetime. the best minds cant even get electric cars right now, so why even dream of electrifying a commercial aircraft. get the tech right with cars, where the worst thing that happens is a couple of people die when the battery bursts into flames, as opposed to 100's.
              What are you talking about? Electric cars are making an amazing progress, there will be no more fuel cars sold in a couple of decades max. Yes, batteries can catch fire, so does gasoline. And the rate at which fuel cars catch fire is greater than the rate at which electric cars catch fire (weighted by population, so its not that there are fewer electric car fires because there are fewer electric cars).

              Other than that, I agree the technology in not anywhere near to be used in commercial planes. The main reason being that the density of energy in the best batteries available (both in terms of energy per unit weight and energy per unit volume) is horribly bad compared with chemical fuels. I even think that hydrogen-based fuel cells will not work (which is the direction that Airbus is going), I think that the primary direction for a greener aviation will be bio and synthetic fuels that don't release the carbon trapped in the fossil fuels but make fuel from carbon in the atmosphere, and using renewable energies to run the process that makes that fuel. In this way, the engine technology remains the same, you will still be using JET-A just from a renewable source.

              --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
              --- Defend what you say with arguments, not by imposing your credentials ---

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              • #8
                Originally posted by Evan View Post

                Apparently, well-made, undamaged batteries do not burst into flames any more than well-made, undamaged fuel tanks do.

                Airbus is exploring the hybrid route now with their E-Fan X research aircraft. This is testing a 2700hp electric motor in the #3 position of a BAe 146, with electric generation powered by an AE2100 turboshaft similar to the ones used on the C130J. Obviously, getting 2700 electric hp from a 4600hp turboshaft isn't what you could call efficiency but the point of this endeavor is to develop technology, not efficiency. However, they also install a 4400lb battery providing 2MW which equates to the same 2,700hp. The trick is to lose the hybrid aspect, the turboshaft. I suspect the work being done now anticipates further breakthroughs in battery and motor tech that will one day result in a battery 'fuel weight' needed to match turbofan ranges. There are other challenges, such as thermal issues (cryogenics may play a role) and high altitude corona effects (pressurization may be needed) and a lot of electromagnetic shielding. Will it ever be practical to pump 15MW of power into a wide-body, long-haul airliner...?

                In the nearer term, hybrids powered by two electric fans and two turbofans could allow descent phases to be flown on electric alone, although I would expect the turbofans to be left at flight-idle anyway in case a go-around or emergency ascent is needed. So I'm not really seeing the payoff there.
                Again, I don't see much future for hydrogen in aviation (or even in cars). I think that if planes go electric some day, it will be with synthetic liquid fuel feeding fuel cells. But if the synthetic fuel becomes economical feasible (because it's already proven to be technically feasible) then the first step will be to feed regular engines with this fuel. The battery cells will only make sense if tthe combination of makin electricity out of the fuel and then running an electric motor becomes more efficient than using the fuel to run a a gas turbine. If that happens, then you "fuel equivalent to electricity" concern becomes irrelevant.

                --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                --- Defend what you say with arguments, not by imposing your credentials ---

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                • #9
                  i have no idea if this guy has any credentials, but his math seems to be on point. perhaps this is a good starting point as to why e-aviation is a loooooooooooooooong way off. https://www.youtube.com/watch?v=w__a8EcM2jI

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                  • #10
                    Originally posted by Gabriel View Post

                    What are you talking about? Electric cars are making an amazing progress, there will be no more fuel cars sold in a couple of decades max. Yes, batteries can catch fire, so does gasoline. And the rate at which fuel cars catch fire is greater than the rate at which electric cars catch fire (weighted by population, so its not that there are fewer electric car fires because there are fewer electric cars).
                    apples to oranges. fossil fuel vehicles VERY rarely spontaneously burst into flames. the same CANNOT be said for current battery tech powered vehicles.

                    for christ's sake! you can't even check 1 ounce lithium battery now. that should tell you all you need to know about current battery tech... also, recall the dreamliner battery issues? i assume boeing was not using cheesy batteries. they still spontaneously burst into flames.

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                    • #11
                      Originally posted by TeeVee View Post
                      i assume boeing was not using cheesy batteries.
                      Well, I hate to break it to you but...


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                      • #12
                        Originally posted by TeeVee View Post

                        apples to oranges. fossil fuel vehicles VERY rarely spontaneously burst into flames. the same CANNOT be said for current battery tech powered vehicles.

                        for christ's sake! you can't even check 1 ounce lithium battery now. that should tell you all you need to know about current battery tech... also, recall the dreamliner battery issues? i assume boeing was not using cheesy batteries. they still spontaneously burst into flames.
                        There were almost 190,000 vehicle fires in the U.S. in 2019, and they happen in gasoline vehicles at a much higher rate. It notes that from 2012 to 2020 there was about one Tesla vehicle fire per 205 million miles traveled—versus one per 19 million miles traveled for all types,
                        https://www.greencarreports.com/news...s-gas-vehicles

                        --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                        --- Defend what you say with arguments, not by imposing your credentials ---

                        Comment


                        • #13
                          Originally posted by Gabriel View Post
                          I agree the technology in not anywhere near to be used in commercial planes. The main reason being that the density of energy in the best batteries available (both in terms of energy per unit weight and energy per unit volume) is horribly bad compared with chemical fuels. I even think that hydrogen-based fuel cells will not work (which is the direction that Airbus is going), I think that the primary direction for a greener aviation will be bio and synthetic fuels that don't release the carbon trapped in the fossil fuels but make fuel from carbon in the atmosphere, and using renewable energies to run the process that makes that fuel. In this way, the engine technology remains the same, you will still be using JET-A just from a renewable source.
                          I'm pretty much of the same mindset. There are a lot of places where electrical power can easily replace fossil fuel (assuming it comes from renewable sources) but, for the reasons you just stated, aviation isn't one of them. If we could move much of the world's terrestrial power to renewables, it's possible that we could continue to burn JET-A and still avoid climate disaster. But let's assume that we aren't going to do that, because industry probably isn't going to do that.

                          I take it you are referring to synthetic fuels that use hydrogen to extract CO2 from the atmosphere. To begin with, this is only a carbon neutral solution. It won't help the world from exceeding the 2 degree warming threshold. And it's only a carbon neutral solution if the hydrogen is produced with renewable energy. Scale this up to the needs of global aviation and I doubt this is going to be the case. Of course, the same thing can be said about electrical generation for battery power.

                          To avoid disaster, we need to REDUCE carbon in the atmosphere.

                          Synthetic fuels, to be competitive, also depend on carbon pricing mandates placed on fossil fuel, so, for this to work, fuel costs will have to go up and thus ticket prices. But this might be a good thing since the only way to keep commercial aviation from contributing to the destruction of the environment, whether with synthetic fuel or battery power or JET-A is for everybody to fly less often.

                          At least until those compact fusion turbines come to market...

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                          • #14
                            Yes, all the renewable energy solutions tend towards carbon neutral (at best). The solutions to capture carbon exist (from forestation to, well, atmospheric carbon capture and putting it in concrete or burring it) but these don't produce energy. On the contrary, they consume energy that better comes from a carbon-neutral source. In for the humans to have a greenhouse gasses neutral footprint, we will NEED carbon capture, because all renewables are not carbon neutral. Not until all the industries get their energy from renewable sources.

                            Actually, I think that one of the most powerful and quick tacks to electrification tending to carbon neutral is going nuclear. I really don't understand why the world is moving away from that. It seems to work quite well for example in France, where ~70% of the electrical power comes from nuclear plants.

                            --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                            --- Defend what you say with arguments, not by imposing your credentials ---

                            Comment


                            • #15
                              Originally posted by Gabriel View Post
                              Actually, I think that one of the most powerful and quick tacks to electrification tending to carbon neutral is going nuclear. I really don't understand why the world is moving away from that. It seems to work quite well for example in France, where ~70% of the electrical power comes from nuclear plants.
                              The main problem with fission is that it produces toxic radioactive waste that will remain toxic for far longer than any containment system we can foresee. So, unless we shoot it into deep space, we are just making time bombs.

                              Did you know that nuclear powered aircraft were once actually a thing? Definitely not a good thing.

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