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.
So Much LUDD.. (Score:3, Insightful)
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.
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I don't think commercial jets have any internal combustion engines. But why do you think they'll become "non-viable" in the future?
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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.
Jet engines are internal combustion engines (Score:2)
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.
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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)
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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
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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.
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About 1% as often as people who said things were 'just around the corner' have been proven wrong.
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:) 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.
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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
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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.
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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)
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.
Re:All for free!!!! (Score:5, Insightful)
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Exactly. 'New shiny' people are chumps.
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i like to have Bacos and cheddar cheese with my word salad.
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Someone just managed to NOT hide an electric motor in a bike.
You will never know about the ones who did hide it.
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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
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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.
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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%.
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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.
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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?
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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
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I think the point was to try to avoid running the APU and the engines which are very inefficient, polluting, etc.
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No, the point was to generate free advertising. They have to run the APU or an engine anyhow.
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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
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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)
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.
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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?
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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
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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
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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)
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)
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.
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.
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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.
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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.
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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.
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Motors in wheels as part of the package ... hmm (Score:4, Insightful)
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.
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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.
Re:Motors in wheels as part of the package ... hmm (Score:4, Interesting)
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.
Re:Motors in wheels as part of the package ... hmm (Score:5, Informative)
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.
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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.
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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).
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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
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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
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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
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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
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The motors would probably not be geared at all, but mounted right inside the wheels themselves, or on the axle. Large stator with many poles, capable of working well at low (for an electric motor) speeds. Reliable and lightweight motor/generator electronics already exist for electric cars.
Perhaps, but that nasty certification test where they run the aircraft fully loaded at take off speed then abort using only brakes is going to be a PITA to pass. Right now the biggest problem is the tires catching fire from all the heat from the brakes, now you want to add a bunch of wire, insulation, electronics and other junk to the wheel assembly which is already stuffed with brake rotors, pads, hubs and aircraft rubber? If you get the aircraft to actually stop during this test, you'd better bring a la
I can see the headlines: Mini-Hindenburg! (Score:2)
Let's keep things simple (Score:2)
Not sure I want any part of the plane, including landing gear, to be any more complex than absolutely necessary.
Not sure one airline alone can do this (Score:2)
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.
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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.
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They already have tire tread patterns that spin the tire up when the wheel goes down.
The Air Force used them for a period 20 some years ago and found them to not be cost savers.
No way it is getting certified in 10 years (Score:2)
Other budget airlines respond (Score:2)
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 will go nowhere (Score:2)
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
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The Internet tubes have already been pre-treated with filth.
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If only there was some way to carry a tank of brine solution on board an aircraft...
Re:fresh clean water? (Score:4, Insightful)
You would need so little salt to treat the water that the tank would be insignificant in mass compared to the fuel cell equipment, or even the other food service equipment on board.
This idea has many, many problems with it - but "pure H2O" is not one of them.
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to put some perspective on this (i know this is /. but..)
the galley CURRENTLY has enough salt to "treat" any recovered water. (any in flight service folks pop quiz how many salt shakers are normally stored in the galley??)
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And just to give you some numbers to play with... MAXIMUM recommended dissolved solids in drinking water is 500mg/L. An Airbus A380 carries 1700 L onboard. Thus the weight of the water is 1700kg and if all of that water was grossly overtreated to the maximum limit, you would need to carry 0.85kg in solids with you.
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LOL, now you are stretching.
No, I'm still using a tank of brine solution - but it only needs to contain a kilogram of actual solids. That's a small tank compared to the 1700kg worth of water that you would otherwise be carrying.
But I'm happy to concede that you could solve this with other means besides a brine tank. Either way, it's a very solvable problem and would not hold up such a project.
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He seemed to be worried about the plane's plumbing, so I gave him a solution. The whole post is ridiculous and I'm not sure why I posted a reply. As if containing distilled water were not a solved engineering problem.
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As if containing distilled water were not a solved engineering problem.
Ah, but you're forgetting how utterly corrosive and powerfully toxic pure water is ;-)
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Pure H20 is so corrosive you need special tubing for it. You sure this is a great idea?
Yet another reason this is a really BAD idea...
1. Hydrogen is an explosive risk when stored
2. Storing quantities of hydrogen sufficient to power anything requires either pressurization, very cold temperatures or both and the equipment to do this is pretty heavy if you wish to avoid the problem #1
3. Industrial sources of Hydrogen cause a LOT of CO2 emissions or are environmentally very unfriendly.
4. Fuel cells are pretty inefficient, so it takes a lot of fuel and oxidizer to obtain a specific amount of
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AC...super-genius!
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You apparently do not know much about fuel cell technology. The hydrogen can be electrolyzed out of water using solar energy, and there's not much of it at any given time as it is then fed into the fuel cell and converted to electricity and water.
Oh I know enough about fuel cells to understand this, you need hydrogen to run them (Assuming you are using a hydrogen based cell). Hydrogen that has to come from someplace and that must be supplied in quantity with an oxidizer to the Fuel Cell to allow it to produce electrical energy.
Using electricity to split water is a pretty horrid energy waster. I takes quite a bit more to split than you can ever get back from the fuel cell. There are much more efficient, less energy consuming ways to get hydrogen t
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>> refill the planes' water systems
This is bullshit anyway.
If you drink the water, or flush it, where would you get the water from when you brake at landing ?
>> Hydrogen Fuel Cells For Taxiing
Fuel cells ? Inefficient.
https://www.youtube.com/watch?... [youtube.com]
Re:fresh clean water? (Score:5, Funny)
You'd also need special humans for it. Pure H20 cannot be consumed by humans [...]
Life Hack: Pure H2O becomes safe to drink by adding a sticker that says; "Gluten Free".
I tried it and it totally works!
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Bought into the bottled water mafia hey? I grew up drinking distilled water. Many people in my home town had distillers.
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Pure H20 cannot be consumed by humans .
No problem.
Re:fresh clean water? (Score:5, Funny)
Pure H20 cannot be consumed by humans.
Flint Michigan public utilities, plz go.
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Pure H20 cannot be consumed by humans .
Of all the completely ridiculous asinine made-up bullshit I've read on /. over the past decade, this is the tops o' them all.
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Distilled water will kill you if you drink too much of it.
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Any water will kill you if you drink enough of it.
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of course dosage matter. Strychnine in small doses is OK. But it will kill you faster than salt water.
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So how often do people request their water intravenously on a flight?
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Sigh yourself. Did you know that the Apollo astronauts all drink water that came from a fuel cell? Yes, long term you would develop an electrolyte imbalance drinking only ultra pure water (which is not what comes out of fuel cells) much as you would if you ate only food that had all salt removed from it. If you're concerned about it, eat a snack sized bag of chips when you land.
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The AC I replied to apparently thinks they wouldn't but I suspect they would.
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That link has to do with over drinking water related deaths such as water drinking contests.
It has nothing to do with pure/distilled water.
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Distilled water is not isotonic. Go tell hospitals they are loons for using 5% isotonic solution for their IVs.
https://en.wikipedia.org/wiki/Water_intoxication
Osmosis, they taught me that in high school. You?
Did you read the article you linked?
Water is considered the least toxic chemical compound, with an LD50 of over 90 ml/kg in rats
hyponatremia was just as likely to occur in runners who chose sports drinks as those who chose water
So.. yep, it is toxic if you drink too much. So is isotonic solution. The article you linked even cites court cases where hospitals have been sued for causing water intoxication via IV...
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This sounds suspiciously like a perpetual motion machine.
Only if you ignore the fact that the energy they're re-capturing was generated by the plane's jet engines during flight, rather than by this fuel cell. It's just a form of regenerative braking, no different than the flywheels commonly in use in automobiles today. And they said they'd be using the energy to power the plane on the ground. Water is a natural byproduct of the energy production, rather than the goal.
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The cycle from electricity to H2 generation, storage and burning in a fuel cell is only about 22% efficient.
This seems like a lot of trouble to go to on a very inefficient process.
Might be better to use batteries to capture the electricity (and these can be supplemented on the ground by plugging it into the grid). Electricity to battery round trip can be better than 90% efficient.
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It depends, but electrolysis efficiency may be at least 0.70% without heat capture or 0.86% with. Fuel cell efficiency may be around 60%. Which leaves as with 0.42%. It is not perfect, but much better than just discarding all this energy as it is done now.
Only some delusional Musk cult member may suggest to use lithium batteries for any significant energy storage on an airliner. You would waste much more energy to carry them than they can store - airliners are not golf carts. To get 777 over Atlantic you ne
Re: Things that make you go "hmmm..." (Score:2)
But we only want to get the airliner from the gate to the runway.
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How much of that is carried on the airplane? Nobody ever said turbines are efficient. Just that they are capable of powering airplanes. Unlike fuel cells.
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A plane traveling at 500 miles per hour, at an altitude of 40,000 feet, has to lose a huge amount of both kinetic and gravitational potential energy before it's stationary on the runway. If you can capture 1% of this, then you can taxi around the airport for quite an extended period.
Just add, "Calculate this extended period of time" and you'll have one of those math word problems I hated back in school. Will this be on future SATs :-)
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Hydrogen in aircraft? What could possibly go wrong? https://en.wikipedia.org/wiki/... [wikipedia.org]
We should ban that jet fuel stuff too while we're at it! Have you seen how dangerous it is?! https://www.youtube.com/result... [youtube.com]
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BIG difference... As a liquid Jet A is pretty nearly inert, you have to vaporize it to make it burn well, either by spraying it into air or heating it until it boils. It doesn't explode as a liquid sitting in a tank, even if you throw in burning objects. It is REALLY hard to keep hydrogen in a liquid state because of the pressures and temperatures involved in it's storage. Hydrogen gas is highly explosive when mixed with some oxidizer and it's really hard to keep it from doing that. Jet A can be safely
Re: Hydrogen in Aircraft (Score:2)
How dangerous can it be? It can't even melt steel beams.
Weight, What? (Score:2)
How many hundreds of pound will this add?
It's not clear to me how having a battery on board is going to move the plane from the terminal to runway the and back again without embedding some sort of drive mechanism in the wheels. Unless a fuel cell produces thrust? WTF.
Me thinks the technical details have been utterly muddled by the original FA.
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Then you need to compress it to a liquid.
Why? High pressure gas might be sufficient.