Follow Slashdot stories on Twitter

 



Forgot your password?
typodupeerror
Check out the new SourceForge HTML5 internet speed test! No Flash necessary and runs on all devices. ×
Transportation Power

EasyJet May Trial Hydrogen Fuel Cells For Taxiing (thestack.com) 150

An anonymous reader writes: Low-cost airline easyJet is discussing plans to install hydrogen batteries as part of a proposed zero emission fuel system, which would power its aircraft during taxiing. The budget service revealed designs for a hybrid plane this week, and said that it would begin trialling the technology later this year. The system will involve embedding a hydrogen fuel cell on board the aeroplanes, with the energy captured from the brakes on landing able to power the jet on the ground. As the only waste product from a hydrogen cell would be fresh, clean water, Ian Davies, head of engineering at easyJet, also suggested that this could be used to refill the planes' water systems during the flight, providing a water source for passengers to drink and for flushing toilets.
This discussion has been archived. No new comments can be posted.

EasyJet May Trial Hydrogen Fuel Cells For Taxiing

Comments Filter:
  • So Much LUDD.. (Score:3, Insightful)

    by Anonymous Coward on Tuesday February 02, 2016 @12:46PM (#51421717)
    Five comments in, and the signal-to-LUDD ratio from the Luddites has already dragged the conversation so far below the noise floor that it's not even a conversation anymore, just LUDD LUDD LUDD.

    Guess what? Internal combustion engines of any kind will, at some point in the future, become non-viable. We'll have to come up with alternatives or lose much of our transporation capabilities. What they're doing here doesn't have anything to do with propulsion during flight, but at least someone is trying to think outside the proverbial box.
    • by ceoyoyo ( 59147 )

      I don't think commercial jets have any internal combustion engines. But why do you think they'll become "non-viable" in the future?

      • Turbines are 'internal combustion' even though you can see light through them.

        AC is drinking the coolaid. Likely expects battery powered airplanes real soon now. Heard the words 'noise floor' somewhere but doesn't know what it means.

      • I don't think commercial jets have any internal combustion engines

        Umm, what do you think propels the plane? Unicorn farts and pixie dust?

        Planes are propelled by burning jet fuel (combustion) within a turbine (internal). You might consider learning what an internal combustion engine [wikipedia.org] actually is before saying something so dumb publicly.

      • All of today's jet planes are internal combustion engines. Steam locomotives are not ICEs. Steam jets are not ICEs, but there are no coal burning, steam jet airplanes that I know of.

        ('Twould be a neat steampunk idea though. Maybe do it up in Blender)

    • by caseih ( 160668 )

      Yes, but that point is farther in the future than most people who are pushing batteries will admit. Internal combustion engines of all kinds will be viable for years to come. Even with the thermal efficiency capped by the laws of physics, the energy density of hydrocarbons is so great and the infrastructure to handle it so easy, it is still a winner over batteries and electrics. Pollution will always be a concern, though, but CO2 need not be, as hydrocarbons may be a convenient way to store renewable, ca

      • Yes, but that point is farther in the future than most people who are pushing batteries will admit.

        How many times have people who said that is farther in the future than people think been proven wrong? You may be right in this case but I wouldn't put good money on it.

        • About 1% as often as people who said things were 'just around the corner' have been proven wrong.

          • :) You may be right in general. I was thinking in terms of the renewable energy field where wind and PV Solar are now competitive with fossil fuel generation and in electric cars where the development continues to outpace many predictions from 10 years ago.

      • Or do it up proper and get rid of the undercarriage, and have the plane mate with an electrically driven cradle on the runway. We've got the technology to do that now. The only thing to fear is fear of a new idea.

        We also have the technology to convert passenger and cargo jets to drones, flown by operators on the ground. Get rid of the flight crew. Each airport would have its own corps of operators specialized in landings and take-offs at that airport, with hand-offs to regional operators who manage the hig

        • Or do it up proper and get rid of the undercarriage, and have the plane mate with an electrically driven cradle on the runway.

          I love that episode of Thunderbirds.

    • by mjwx ( 966435 )

      Five comments in, and the signal-to-LUDD ratio from the Luddites has already dragged the conversation so far below the noise floor that it's not even a conversation anymore, just LUDD LUDD LUDD.

      Guess what? Internal combustion engines of any kind will, at some point in the future, become non-viable. We'll have to come up with alternatives or lose much of our transporation capabilities. What they're doing here doesn't have anything to do with propulsion during flight, but at least someone is trying to think outside the proverbial box.

      Erm, no.

      Petroleum based fuels may at some point in the future (a very, very long way away in the future, there is more oil on the planet than people know about) become enviable, but the principle of ICE's will remain viable, they'll just switch to a new fuel source.

  • All for free!!!! (Score:5, Interesting)

    by OzPeter ( 195038 ) on Tuesday February 02, 2016 @12:47PM (#51421723)

    The system will involve embedding a hydrogen fuel cell on board the aeroplanes, with the energy captured from the brakes on landing able to power the jet on the ground. This technique is similar to the high-end kinetic energy recovery systems (KERS) used in Formula One cars, which store recovered energy to later use for acceleration.

    TFA mentions harvesting the braking energy as being similar to KERS used in Formula 1. But no mention is made of the additional mass or equipment (unsprung at that) that would be needed to be added to the landing gear in order to harvest that energy. Such equipment needing to be robust and large enough to capture a worthwhile amount of energy in the 10 seconds of braking that a plane experiences when landing. For the rest of the 99.9999% of the flight this is dead weight that the plane has to burn fuel in order to carry it around.

    So color me surprised if anyone really thinks that is practical. (let alone the bizarre notion that the recovered energy could somehow be funneled into a hydrogen based fuel cell - super cap yes! fuel cell ? are you kidding me?)

    It would probably make more sense to assign a tractor to drag each aircraft from the gate to the start of the runway rather than use the planes fuel to taxi around.

    • by gweilo8888 ( 921799 ) on Tuesday February 02, 2016 @12:56PM (#51421765)
      What he said. This is buzzword-salad hype from EasyJet to get some free advertising from the media. Nothing more, nothing less.
    • Presumably the same equipment that is moving the plane by electrically driving the wheels during taxiing, so there's a few tenths of a percentage point off that dead weight figure. OTOH someone just managed to hide an electric motor inside a racing bicycle, I'm sure one of those teeny little things can move an airplane . . . not.
      • Someone just managed to NOT hide an electric motor in a bike.

        You will never know about the ones who did hide it.

    • While the idea of using a fuel-cell powered electric motor to drive the aircraft to the end of the run way before powering up the engines is a bit out there, there are a number of companies that are looking into a providing motors that fit into the landing wheel hubs (I know of at least one such company providing nose wheel motors for taxying for the B737 and A320 - http://www.wheeltug.com/ [wheeltug.com]).

      Apparently it does make a lot of sense to do this in terms of fuel savings. I'm not sure if a fuel cell improves on

      • That runs on the APU. I'm pretty sure the fuel cell or batteries needed to power the wheel would kill the economics of the whole thing.

        Even for 'wheeltub', I'm willing to bet it's only a net gain on short hops.

      • by mspohr ( 589790 )

        Batteries would be much more efficient for capturing this energy and they could be easily charged at the gate. Battery round trip efficiency is about 90%, hydrogen fuel cell about 20%.

        • by OzPeter ( 195038 )

          Batteries would be much more efficient for capturing this energy and they could be easily charged at the gate. Battery round trip efficiency is about 90%, hydrogen fuel cell about 20%.

          You should know from your car analogies that the energy density of a battery is much less than that of gasoline. So adding batteries is going to be a net loss to efficiency.

          • by mspohr ( 589790 )

            I'm not sure batteries would be a good solution. I was just pointing out that they are much better than a hydrogen fuel cell.
            Gasoline?

        • Why bother carry batteries around? They are heavy and horribly inefficient. Just crank up the APU that runs on Jet A. You are going to need the APU to get the main engines started or run the air-conditioning system using bleed air, the power it produces to keep the lights and radios on anyway, just add a few HP for driving the traction motors in the wheels...

          But wait.. That doesn't look new and shiny or appeal to the environmental crack heads who soon at anything labeled "green" so it won't give the airl

          • by mspohr ( 589790 )

            I think the point was to try to avoid running the APU and the engines which are very inefficient, polluting, etc.

            • No, the point was to generate free advertising. They have to run the APU or an engine anyhow.

            • I think the point was to try to avoid running the APU and the engines which are very inefficient, polluting, etc.

              The APU is there for a reason and it's not going away in a modern airliner where AC and power is required to keep the passengers comfortable and happy, start the main engines, and serve as an emergency power supply in the not so unlikely even of a generator failure on the main engines. The jet fueled APU is going to stay, and likely has the capacity to run any electric motor thingy you can imagine might actually save the environment, and won't add unnecessary weight or fuel consumption to the aircraft. B

              • Agreed with everything you said up until the point of "It will be easier and safer..."

                I don't know how familiar you are with airport operations but adding additional equipment on the tarmac to the runway adds considerable complexity to aircraft movements which have to be tracked and controlled by the tower. This added complexity has a potential impact on safety as having tugs moving around (manned or autonomous) means that their needs to be new procedures in making sure they don't move in front (or behind

    • Re:All for free!!!! (Score:4, Interesting)

      by dj245 ( 732906 ) on Tuesday February 02, 2016 @01:16PM (#51421929) Homepage

      The system will involve embedding a hydrogen fuel cell on board the aeroplanes, with the energy captured from the brakes on landing able to power the jet on the ground. This technique is similar to the high-end kinetic energy recovery systems (KERS) used in Formula One cars, which store recovered energy to later use for acceleration.

      TFA mentions harvesting the braking energy as being similar to KERS used in Formula 1. But no mention is made of the additional mass or equipment (unsprung at that) that would be needed to be added to the landing gear in order to harvest that energy. Such equipment needing to be robust and large enough to capture a worthwhile amount of energy in the 10 seconds of braking that a plane experiences when landing. For the rest of the 99.9999% of the flight this is dead weight that the plane has to burn fuel in order to carry it around.

      So color me surprised if anyone really thinks that is practical. (let alone the bizarre notion that the recovered energy could somehow be funneled into a hydrogen based fuel cell - super cap yes! fuel cell ? are you kidding me?)

      It would probably make more sense to assign a tractor to drag each aircraft from the gate to the start of the runway rather than use the planes fuel to taxi around.

      Not to mention that you can't start a gas turbine and immediately subject it to full load. It needs several minutes to heat up, bring the oil to operating temperature, and get any temporary "bow" out of the turbine rotor. Going from idle to full power (as in every takeoff ever) on a warm engine is somewhat detrimental to the engine since it results in huge temperature differentials. The engine is designed to handle this, but shortening the taxi/idle time is not a good idea and probably is outside of the turbine manufacturer's original design intentions.

      • by OzPeter ( 195038 )

        Not to mention that you can't start a gas turbine and immediately subject it to full load. It needs several minutes to heat up, bring the oil to operating temperature, and get any temporary "bow" out of the turbine rotor.

        I'm no expert in gas turbines but I appreciate the need to warm them up. With that said, can there be fuel savings made between leaving the gate and bringing the engine to an operational status just prior to reaching the end of the runway? Or is taxi-ing a part of the warm up profile of the engine?

        • Turbines take a long time to warm up. Now I'm sure this depends on the airport, being stuck on a taxiway in LAX probably could have some fuel savings compared to a small airport, but even when you go on a perfectly empty airport there's still a significant warm up period. The longer the better. In industries where longevity is critical and where warm up times are not causing people to wait on runways you can often see turbines at idle speed for 30min to several hours. Typically the bigger the turbine the lo

        • by dj245 ( 732906 )

          Not to mention that you can't start a gas turbine and immediately subject it to full load. It needs several minutes to heat up, bring the oil to operating temperature, and get any temporary "bow" out of the turbine rotor.

          I'm no expert in gas turbines but I appreciate the need to warm them up. With that said, can there be fuel savings made between leaving the gate and bringing the engine to an operational status just prior to reaching the end of the runway? Or is taxi-ing a part of the warm up profile of the engine?

          I am not an expert in aviation turbines, but the land-based ones generally need about 10 minutes between starting and full load. This varies by manufacturer and by model. On the land side, most machines have an Equivalent Operating Hours (EOH) counter built into the control system. An hour operating under typical conditions is 1 EOH. A cold startup can be counted anywhere from 25 to 100 EOH depending on the manufacturer. Other events, such as an flame-out, compressor stall, hard shutdown, emergency sto

    • by ceoyoyo ( 59147 )

      Starting a jet engine isn't just pressing a button. I don't think airports would particularly appreciate every airliner sitting on the runway threshold firing up it's engines. I suppose you could use this for taxiing from the runway to the terminal, but there usually aren't many holdups in that process.

    • Re:All for free!!!! (Score:5, Interesting)

      by yodleboy ( 982200 ) on Tuesday February 02, 2016 @01:41PM (#51422147)
      "It would probably make more sense to assign a tractor to drag each aircraft from the gate to the start of the runway rather than use the planes fuel to taxi around."

      I was thinking the same thing... wouldn't it make sense to use autonomous tugs powered fuel cell, then tug the planes to the end of the taxiway? most of the tugs i've seen require manual connect/disconnect, so you'd have to automate that. unhook at end of taxi way, and pilot moves onto runway under own power, since you don't want anything else on an active runway. robo-tug heads back to terminal and to next assigned gate.

      I just figured out the fatal flaw... pilot and ground crew unions would never allow it...
    • Re:All for free!!!! (Score:5, Interesting)

      by Solandri ( 704621 ) on Tuesday February 02, 2016 @01:47PM (#51422199)

      For the rest of the 99.9999% of the flight this is dead weight that the plane has to burn fuel in order to carry it around.

      If I remember right, if a stewardess loses a sugar packet in some crevice of an airliner, the extra weight (4 grams) will cause an additional half liter of fuel burn in a year.

      It would probably make more sense to assign a tractor to drag each aircraft from the gate to the start of the runway rather than use the planes fuel to taxi around.

      That actually brings up another problem with the idea. The point of moving around under your own power while on the ground is so that any immediate problem with the engines or fuel reveals itself during taxi when you are nice and safe on the ground. Not when you are 10,000 ft in the air hurtling at 400 mph.

      I'll also add that the energy from combining hydrogen and oxygen to form 1 liter of water releases 237.14 kJ/mole (Gibbs free energy). 1 mole of water is about 18 grams, so 1 liter of water is formed for every 13.15 MJ released this way. An A320 has a maximum landing weight of 66 tons, so figure it's about 60 tons in regular service with a full load. Stopping from a landing speed of 135 knots, that's 252.5 MJ of kinetic energy. Enough to convert just 19 liters of water into hydrogen and oxygen at 100% efficiency. However, some of that kinetic energy is shed by the spoilers and thrust reversers, not the brakes. Frankly I'm not even sure that's worth the extra weight of machinery to recover.

      Summing all this up, the maximum energy you can recover from braking an A320 at landing is equivalent to 5.5 kg of aviation fuel (46 MJ/kg). At a (realistic) 25% conversion efficiency for the fuel, and (optimistic) 60% conversion efficiency for the electrolysis and 70% efficiency for the hydrogen fuel cell (42% overall), this device will basically be reducing your fuel requirement by about 9.24 kg (11.5 liters). Every 8 grams the device weighs more than that will result in an extra liter of fuel burn per year than just carrying around the extra fuel.

      • by OzPeter ( 195038 )

        I was doing similar calculations for an A-380 but I doubted my results as they pointed to rate of energy recovery being in the order of a small power station for 10 seconds.

      • The point of moving around under your own power while on the ground is so that any immediate problem with the engines or fuel reveals itself during taxi when you are nice and safe on the ground.

        Warming up the turbines also has a huge part to play in the taxing process.

    • by caseih ( 160668 )

      Also any regenerative hardware will have to be physically attached to the wheels adding all kinds of rational inertia to the wheels. Landing is already hard on wheels as they go from a dead stop to spinning in a second. The generator hardware would make the tires take more load during this critical moment.

      • The generator hardware could be used as a motor to spin up the wheels to match ground speed prior to landing. This would greatly reduce wear on the tires and might allow lighter landing gear due to reduced peak load on landing. The savings might compensate for some of the added weight.
  • by enjar ( 249223 ) on Tuesday February 02, 2016 @01:01PM (#51421809) Homepage

    Not mentioned in the blurb is that this also includes putting motors in the plane's wheels and adding controller hardware. That's going to add on weight to the plane, as I can imagine a set of electric motors (and associated gear trains, etc) that can move a plane that weighs something like 100,000-150,000 lbs are exactly "light". Plus there is the difficulty of packing it all into the landing gear, where there's not exactly a lot of room. You could do a hydraulic drive of some sort, but then you have the pump and motor sitting somewhere, too, plus the weight of the hydraulic fluid.

    Less sexy would be to develop a tug that could not only push the plane back, but also perform taxi duties. You could have that thing run on batteries, fuel cells, etc -- and you don't have to fly it everywhere with you.

    • Doesn't matter. The plane needs to run at least an APU for air conditioning anyhow.

      You could conceivably put all the support equipment into a tug and have the tug disconnect just before takeoff. But I bet they want the engines at operating temperature before they open them up.

      • by enjar ( 249223 ) on Tuesday February 02, 2016 @01:33PM (#51422079) Homepage

        Right. What I was getting at is that the blurb and accompanying article seems to almost imply that through some magic and a fuel cell the plane could move itself without some means of motive power. Currently this comes from the jet engine and that's it (barring, of course, external sources like a tug). Adding that motive power would add weight. Other non-sexy things might include some sort of chain embedded in the taxi way that could grab onto the front wheel of the plane, similar to the systems that bring a car through a car wash. The tug could get the plane out to this system and pull it along until it got to where it needed to go. Given that this is a system that would be in one place, and likely using electric power, you could generate those electrons in whatever eco-friendly way you wanted. Of course, this also hand-waves about a billion engineering difficulties away, as well -- chain strength, debris getting in, weather, etc. And then you could use the hand waving to extend the idea to use a catapult system to launch your commercial jet, just like an aircraft carrier ... which is happening with electricity nowadays ... just scale it up, that's easy, right?

        Your point about operating temperature is also a good one. Given that you want the engine making the most power at takeoff, running up a cold engine may not be a fantastic idea. I'm guessing for this use case of frequent short flights that this airline has, the engine is likely up to operating temperature more quickly. For long haul flights, time on the ground will shrink and be dominated by flight time.

    • by brambus ( 3457531 ) on Tuesday February 02, 2016 @01:22PM (#51421971)

      Less sexy would be to develop a tug that could not only push the plane back, but also perform taxi duties.

      This is already done. The pushback tugs are also used for repositioning aircraft between gates and/or hangars. There are many reasons why aircraft start their engines at the gate. This serves primarily as a checkout of the aircraft systems. If an engine behaves oddly, or has trouble starting, pulling back into a gate is simple. Doing it at the runway would be a lot more complicated, as it would require a full back-taxi, which on congested airports is already a major PITA. In addition, many of the internal systems such as flight control hydraulics are powered by the engines, so for example you won't have all flight controls fully functional (meaning, you can't perform a F/CTL check) and you can't fully extend flaps for takeoff unless you have at least one of the engine-driven pumps running. Secondly, the air conditioning packs inside the cabin are engine-powered and they take a lot of juice as well as compressed air (or you'd have to carry a sizable battery just to keep them running for the 20-30 minutes on the ground). On very long taxis to takeoff or after landing, many aircraft already do reduced-engine taxi. 747s routinely shut down 1 or 2 engines right after landing. Twins routinely do single-engine taxi. When there is a long queue for takeoff, similarly, engines get shut down. But doing the whole taxi completely shut down and only starting once close to lining up would probably result in tons of operational complications and possibly safety issues.

      • Twins routinely do single-engine taxi.

        You'll find that twins only do this for really long taxi-ways. The second engine will come on several minutes before the flight regardless to ensure they are warm and ready. Taking a turbine from off to full throttle would result in some very angry reliability engineers throwing stuff at you, likely whatever is left of the turbine.

        • Actually turbine engines tend to require next to no warmup. Unlike piston engines, turbine engines don't have large blocks.
          At least, this is what I've been told by turbine engine technicians and it's been reinforced by never seeing an "engine warmup" requirement in any AFM or operational procedure. For piston engines, warmup is always built into the after start procedure (or equivalent).
          • Funny that's the exact opposite I hear from turbine manufacturers who will require a warmup period as long as possible. Sell something for an aircraft yeah we can get away with a few minutes. Sell the same turbine to drive a gas compressor (there's such a frankenmonster at one of our chemical plants) and the manufacturer delivers a PLC with a hard coded 20min hold at min speed. For warmup

            • It's possible you're not running an aviation-derived engine design such as an LM1500 or LM2500, but instead some bespoke design for industrial turbine engines. I've never seen a warmup requirement on an aviation engine.
              • That's the strange part, it was an aviation engine. Most things I see are bespoke designs that's why this one stood out. But ultimately the requirements are still very similar and it's not a strict requirement such that if you don't do it expect to be collecting small bits of turbine on your runway, it's nearly always related to long-term reliability, primarily reduce wear on rotational components by ensuring thermal expansion is completed before full load (or in many designs before you cross one of the cri

                • That's the strange part, it was an aviation engine.

                  What was it? Just out of curiosity.
                  Anyway, all I can say is I've never seen a warmup requirement in the operating manual of any turbine engine-powered aircraft, but maybe it's because the operational procedures were designed such that it's averted. Warmup is definitely required in piston aircraft (e.g. DA-40; after startup 2 mins idle, then 1200 rpm until oil in green; no takeoff before that). However, in-flight restart procedures don't mention warmup either. You can shut down an engine in flight, leave it

        • by mjwx ( 966435 )

          Twins routinely do single-engine taxi.

          You'll find that twins only do this for really long taxi-ways. The second engine will come on several minutes before the flight regardless to ensure they are warm and ready. Taking a turbine from off to full throttle would result in some very angry reliability engineers throwing stuff at you, likely whatever is left of the turbine.

          Sir, I wish I had mod points for this.

          If airlines didn't keep them separated, removing an engineers boot from a pilots arse would be a regular medical procedure.

          Then again, I've seen this in most industries. Engineers are usually kept separate from operators for good reasons :)

  • Yes, I know there is already a lot of explosive stuff on the average plane, including the door bolts (tell that to the next nervous seatmate you need to avoid). But hydrogen is so memorable in the storied history of aviation. Customers will freak. For economizing on ground time, so much cheaper and simpler to have more and better tugs.
  • Not sure I want any part of the plane, including landing gear, to be any more complex than absolutely necessary.

  • Any major changes to critical flight systems ( landing gear is one I imagine ) would require some serious FAA and manufacturer test and approval program.

    Brilliant idea though.

    • Any entity can hold a Supplemental Type Certificate not just the original manufacturer, and they can even test and fly them as experimental without either manufacturer or FAA or EASA approval - they just cant carry fee paying passengers.

  • If everything has already been developed, tested, proved cost effective and if they are ready to deploy it today and apply for FAA certificate, it would take 10 years before they get it. Plain documentation of what the system is, and FAA failure mode review and the maintenance and certification requirements, additional independent testing by FAA... no way they can get a hydrogen fuel cell into a passenger plane in less than 10 years.
  • Allegiant announced that will do the same thing, and charge passengers a Gee-Whiz Fee for the privilege of being on a plane with experimental technology.

    Spirit announced that on each flight, straws will be drawn to determine which three passengers are fed into the fuel cells, generating power and saving weight at the same time. Next of kin will not get a refund on their tickets, however.

  • This is a lot of hype that the airline is using to get some publicity, and the idea is interesting, but will not take flight (hah). Taxiing is such a minimal part of the fuel burn, and of low relative cost, that the added complexity, not to mention certification hurdles, extra weight, etc. etc. of a new airworthy component will not be worth it.

    You are carrying something with hydrogen (not a huge deal, but extra hurdles), heavy, and interacting with existing aircraft systems.I know of no example (or can

I have a theory that it's impossible to prove anything, but I can't prove it.

Working...