Flight shaming is the hot new thing where people who take more than a handful of trips on an airplane per year are ridiculed for the environmental impact of their travels. It’s one strategy for making flying more sustainable, but it’s simply not viable for ultimately reducing the carbon impact that the airline industries have on the environment.
Electric planes are an interesting place to look for answers. Though carbon-free long haul travel is possible, it’s not a reality for most situations in which people travel today. Current battery technology can’t get anywhere near the energy density of fossil fuels and larger batteries aren’t an option since every pound matters when designing aircraft.
Even with land travel and electric grids improving in their use of renewables and electric power, aviation tends to be difficult to power with anything other than hydrocarbons. Student engineers in the AeroDelft program in the Netherlands have created Project Phoenix to develop an aircraft powered by a liquid hydrogen fuel cell, producing a primary emission of water vapor. So it is an electric plane, but leverages the energy density of hydrocarbons to get around the battery weight problem.
While the project may seem like an enormous reach peppered with potential safety hazards, redundant safety features are used such as sensors and vents in case of a hydrogen leakage, as well as an electric battery in case of failure. Hydrogen produced three times more energy per unit than kerosene, but is six times the volume in gas form and requires cumbersome compression tanks.
Even though hydrogen fuel only produces water vapor as a byproduct, it can still cause greenhouse effects if it is released too high and creates clouds. The team is exploring storage tanks for slow release of the water vapor at more optimal altitudes. On top of that, most hydrogen is produced using steam methane reforming (SMR), creating up to 150g of greenhouse gases per kWh, and electrolysis tends to be more costly and rarely carbon neutral. Alternatives such as solar power, biofuels, and electric power are looking to make headwind as well, but the technology is still far from perfected.
While it’s difficult to predict the success of the project so early on, the idea of reducing risk in hydrogen fuels may not be limited to a handful of companies for very long.
91 thoughts on “Reducing The Risk Of Flying With Hydrogen Fuels”
Sailing ships were carbon-free long-distance travel, centuries before our obsession with fossil fuels began.
What changed is we got impatient. And I think that’s been bad for our health in a lot of ways.
Live life at a relaxed pace. Build modern sailing ships. Read a book.
For anything like that to work, we have to make a complete u-turn in what we consider a responsibly lived life. Right now, the world is fixated on wealth accumulation, and the masses have little choice in feeding the monster just to afford the ever increasing cost of basic necessities. So not enough people can’t simply relax and take 3 months to sail to another continent for vacation. The ones that can are the ones at the top who the masses are frantically working for.
Like so many solutions to problems, they merely (attempt to) address side effects while leaving the source of the problem to undermine the solution in some other way.
I live in a quite different world. Basic necessities get cheaper and cheaper. Everything gets cheaper and cheaper. My phone/movie camera/GPS/WiFi/calculator/check book/tele-viewer is a supercomputer. My car runs forever and so do the tires and brakes. Fuel is as cheap or cheaper than the 1960’s. Really good rice is 18 cents a pound. Electric power is 3.5 cents a kwh. Good machine tools are a few bucks. 32 bit computer boards are $1.50. Where are you?
May be sailing to another continent to have a “vacation” needs to be reassessed.
How about a vacation at home?
In that beloved, expensive, demanding, mortgage inflicted, home.
Most people work night and day to buy and have more and more material things inside … their home.
Why not spending as much leisure time at home as possible?
Like having a vacation?
It’s where I spend my vacation time. I get to do my hobbies for days on end too, while saving potentially hundreds if not thousands of monetary units and indirectly helping save the planet. And also directly helping save the planet with grid connected solar, rain water reclamation for flushing toilets and a second low voltage solar system to run all the household lights, charge phones, even run the TV in the summer months when there is more sunlight than battery capacity.
Why not indeed?
3months? You can circumvent world in that time at ease. Modern sailing yachts are fast, and with weather satelites and meteorology, NY-London if you can live with incinviniences then 4days on racing foiling sailboat is doable. Normal sailors doing live aboard on classical yachts do it in under 10 days. Current records on atlantic passage is 3days 15hours, world circumwention is 40something days. Of course on foiling racing yachts so not convinient for creatures of comfort but if sailing gets mainstream then we can see rapid development in yachts and sailing vessels we can shave a lot of time.
weather satellites require massive amount of energy to be built, put in orbit, and operated.
i doubt very much an economy based on sailing would be able to put satellites in orbit.
The great majority of the planet’s problems have a single source, being too many humans, nearly 8 billion. If we halved this just 3 times, reducing to “only” 1 billion, then 87.5% of current man-made pollution would be cut even if we did not improve our behaviour in any other way at all. So we should start by averaging less than 2 children per mother. Some have zero or one child, so there is still scope for some to have 2 or 3.
As far as hydrogen based flight is concerned, it is possible that the future will see airliners filling up with liquid anhydrous ammonia (NH3) and using fuel cells to convert this to electricity with the exhaust being non-polluting nitrogen gas, as per 78% of the atmosphere, and carbon free.
Liquid ammonia is “safer” than gasoline and pound for pound stores more energy than liquid hydrogen, and is easier to transport etc.
It is easy to create using a “reverse” fuel cell, but the fuel cell technology to convert back to electricity needs considerable improvement and development.
completely wrong but thanks for showing everyone how pervasive the ugly propaganda of eugenics has been ingrained into peoples heads.
the number of people are meaningless we have more then enough food, land and resources to give 10 billion people a good life with just the technology we have today. the world problems have never been caused by a lack of resources or knowledge they are caused by to much greed and not enough will to change.
case in point the problem are not cell phones its that companies expect everyone to buy new ones every 3 months. the problem isn’t getting enough food to people its getting enough purity look foods that people will pay big bucks for that is. the problem isn’t cars its that campanies want everyone person in the family to own two cars and to make those cars over seas so they can make then cheaper.
the problem is your view is it messes the whole point, trying to make a quick fix instead of a fixing the true underlining problem.
“If we halved this just 3 times”
excellent idea. start giving the example and commit suicide. the planet deserves it.
“and using fuel cells to convert this to electricity ”
sure. just need to find a way to build a fuel cell capable of delivering a few dozen megawatt. piece of cake.
something like this, for instance. im sure “progress” will solve the problem of miniaturizing it enough to hang it off the wing of a liner
I think you mean too many plankton. 45 billion tons of the little buggers every year! And they are responsible for the balance of CO2 and Oxygen. Why don’t we have a plan for plankton population control?
The trend was always to go faster. In 1805 my great, great, great grandfather went from the eastern side of North America to where the Columbia River joins the Pacific. It was slow, and they actually visited the Sandwich Islands, fallout from sailing. The return trip was probably more trouble, and longer, since you had to follow the winds.
In the fall of 1964 we went to Europe on a ship, even taking the family station wagon along. That wasn’t a sailing ship, but likely faster. But the end of saiking as travel, planes started getting faster, and cheaper. It’s one thing to take a month to get somewhere, if you are going to stay, but hard to justify if yiu are vacationing for a week.
It’s more than impatience. When my great, great, great grandfather came over from Scotland about 1800, most people never travelled far from where they were born, and if they travelled far, it was often one-way. There’s some speculation that he came to make some h ney abd planned to go back to Scotland, but if so, he stayed for the wife and kids.
The world is smaller because we didn’t stay in the saling era. Travel is cheaper and faster, most don’t want a return to the old days.
Zepplins were “fast” especially the farther you went. But it was luxury travel, being in the air so l made it expensive, as did the few passengers one could carry.
For the record, I’ve never driven a car, amd flown twice, to and from Vancouver in 1986. Most of my travel was by train or bus, and I’ve not been anywhere out of tge city since 1995
Problem solving requires study and understanding, not just applying idealogy.
Tell everyone else how to behave. That’s the ticket!
We don’t have to give up flying, consider the Albatross, to quote Wikipedia..
“Albatrosses are highly efficient in the air, using dynamic soaring and slope soaring to cover great distances with little exertion. It is the only bird that can fly 10,000 miles without landing.”
Using a launching system like on an Aircraft Carrier for takeoff (which uses most fuel), an electric engine and small batteries to give intermittent lift or thrust and continuously updated weather data a large “Albatross” glider could cover the same distance as a regular airplane using much, much less fuel but just taking a little more time.
Albatrosses cover ~1000km/day. I can’t see people being happy with roller coaster ride quality and 40km/h average speed when they could just use a sailboat.
Sail to Denver!?
“Read a book.”
i suggest starting with a book of economics. might explain why people is “impatient” and why mobility is the cornerstone of a wealthy society, where people is so wealthy they can survive ignoring why mobility is important.
Next up, car shaming.
Flight shaming is a good thing and we need more of that.
Yeah, it is a shame the effort and thought wasted on carbon neutrality is not put to positive thinking about how to actually handle and take advantage of any real increases in temperatures. We can make it a bust or a boon. Easy choice I would think.
Shame only works when you care about what others think of you!
This deserves an…UPVOTE!! :-p
Read some Feynman.
Oh my god can we stop the insanity? This community is simply smarter than that right?Does anybody hear remember their six grade science class when we talked about photosynthesis carbon dioxide in the entire organic cycle?
Last time I looked, I never saw a tree eat a lithium battery and return oxygen. To the environment. Seriously.
Have you ever seen a tree fly from new york to london?
Not since the age of steam zeppelins.
I’ve seen a tree fly.
“leverages the energy density of hydrocarbon”
Hydrogen is not a hydrocarbon. It’s just 2 atoms of hydrogen holding hands.
When a mommy and daddy hydrogen atom love each other very very much.
They bang together REALLY HARD and make a helium atom hehe
“So it is an electric plane, but leverages the energy density of hydrocarbons to get around the battery weight problem”
Lol, not hydrocarbons…..hydrogen :)
“So it is an electric plane, but leverages the energy density of hydrocarbons to get around the battery weight problem” = “uses hydrocarbons to produce hydrogen”.
I’m sure it was referring it commercial amounts of H2 coming from natural gas, but should have said so explicitly. Besides, the CO2 is a commercial product as well. Liquid CO2 is a surprisingly commonly use chemical solvent. It will dissolve chemicals like caffeine out of beans without tainting anything.
And where does the hydrogen come from? Generally from electrolysis which just shifts the pollution back to the coal or gas fired power plant.
No different than electric cars which are not green at all.
Electric cars if powered by a gas powered plant are more efficient and put out less carbon than gas cars. Gas plants are *very* efficient (60%) and gas powered cars are very inefficient (20-35%). An additional advantage of EVs is that they use regenerative braking, further reducing the comparative efficiency of gas powered vehicles. And of course about 1/3rd of the US energy mix is nuclear and renewable.
But yes, focusing on planes is just not where to get the most bang for your buck when reducing carbon emissions. Yes these technologies can reduce carbon emissions of flights if powered by renewables, but that same power could instead be used to power the grid and take coal plants offline reducing carbon even more.
Gas plants use methane to produce hydrogen. More fracking is needed.
with coal fired plants, CO2 is the least of your worries… depending on the emission reduction tech installed, they churn out sulfur and nitrogen oxides (good ol’ acid rain and ground ozone in the summer) + ash, both in air and on a gigantic pile next to the plant…said ash is full of heavy metals, arsenic, berillium…all fun stuff and you now have to put it somewhere, so rain water doesn’t leach all the goodies into the water table…
SOFCs producing electricity directly are also 50-60% efficient. One doesn’t necessarily need an engine to run a car on gas. Added bonus: solid oxide fuel cells can operate on any fuel that can be turned into the gaseous state and don’t contain sulfur. That means they run on anything from methane to kerosene and carbon monoxide that would poison the other kind of fuel cells.
The question of whether an electric car makes sense is on whether you need to have a 1,000 lbs battery worth $10,000 and replace it every 10 years, because for the vast majority of the driving public the battery alone costs more than the typical car they’ll buy (second hand). The battery actually costs a significant amount of energy to source all the materials and transport/process/manufacture it:
Li-ion batteries have an embedded energy investment of about 136 kWh/kWh (table 1)
That means something like a Tesla car (100 kWh) takes 13.6 MWh to manufacture, which is enough energy to drive the first 50,000 miles. This is a problem because lithium batteries don’t have infinite shelf life. The average driver takes a 20% efficiency penalty for the amount of miles they manage to drive before the battery is due replacement for old age. Adjust for average transmission loss (-6%), charging and conversion efficiency (-10%) and the powerplant efficiency (-40%), and the efficiency points drop dramatically – and this isn’t even counting the difference in real world energy use vs. EPA or NEDC mileage, or the energy used for heating the cabin which comes for free in regular cars.
In fact, EVs are pretty much on par with a modern diesel car or gasoline hybrids in terms of system efficiency. They just cost more to make.
And regenerative braking for EVs is overhyped. It returns 5-10% of the energy spent. More is lost in the first place by having to haul a massive battery along everywhere.
Regen braking has something of the same problem that makes cylinder de-activation and automatic transmissions not as efficient as they could be… the marketing people are deathly afraid that customers will notice it doing it’s job.
It also has a physics problem. Most stop & go traffic happens at low speeds where the regen efficiency is low or even negative. The faster you go, the better it works when you brake, but the faster you go the less you tend to stop.
But regenerative braking makes for a smooth, relaxed driving experience if you uses the single pedal method in stop & go traffic. And the brake pads last a long time.
It emulates engine braking. Thing is, the drive electronics would be cheaper if you’d just short the motor out for the same effect rather than try to pump the voltage up to charge the battery.
And brakes tend to jam and rust over if you always feather them.
@Luke The drive electronics are no different whether you intend to recuperate energy or not. The power stage already has the switching devices needed, the only difference is the control signals being sent.
Addy: not necessarily. Not all DC motor drives can handle reverse current switching, and AC VFD induction motors need an additional feedback system to keep track of the motor phase angle.
question is from where energy to produce batteries and car comes. If its from renewables or nukes no problem. Smaller efficiency isn’t problem problem is how mutch CO2 and other greenhouse gases we emit. If we don’t stop emission and start catching CO2 from air we are toasted big way. With solid or liquid pollution during production process we can contain it so it will be problem but managable one. As for cost of EV we really need to rethink our transportation needs, big suburbia needs to go, commuting few hours per day needs to end. If we get people back to living in tight cities we can build public transport, use bikes and light ev vehicles that don’t need big batteries or powerfull electric engines.
>”big suburbia needs to go”
It’s a question of cost again. Cramming everyone into the cities causes property prices to skyrocket in and around the city area, and value-producing jobs and industries must move further out to keep costs down, which means people have to commute again to go to work AND pay ridiculous prices for their housing – only in the opposite direction.
Secondly, it’s rather a problem that people concentrate into cities because the cities don’t actually produce real value – they’re places of trade and services and these activities consume value.
The way you make a living in a city is by making other people consume the goods and energy brought in from the outside. With fewer people living outside of cities to produce these resources, all the stuff has to be outsourced and imported from other “less developed” places, which is what’s been happening in all the western countries for the past 50 years. This leads to persistent trade deficits, which is compensated by debt and money printing, financial wars and inflation. Inflation leads to lower real wages, and people in the service economy have to re-double their efforts to sell stuff to each other in order to earn enough money for a living. In other words, it’s an out-of control spiral of consumption.
To bypass the problem of not having access to material goods to sell, people in the service economies have started to produce “immaterial goods”, such as filming youtube videos and “creating content” to milk advertising money out of the other people trying to make you consume the material goods – but this is just wasting electricity to have an excuse to get paid.
That’s why the the cities should be dispersed rather than concentrated for the sake of some apparent “efficiency”. Efficiency of what – making money? People have to go back to smaller communities that can be more self-sufficient in terms of energy and essential resources – to make the wealth for themselves. The urban “services economy” is actually a great burden on the society that cannot be sustained for much longer.
“big suburbia needs to go, commuting few hours per day needs to end. If we get people back to living in tight cities we can build public transport, use bikes and light ev vehicles that don’t need big batteries or powerfull electric engines.”
Love it. Remember the last time? Changing human nature is not easy, but we just marched the uncooperative out into the rice fields and killed them – by the millions. Guess what? And before that in China. And before that in Russia. Guess what again? You kill 100 million, change all the civil institutions, make the new ideas part of school, work, and play, and the uncooperative keep rising out of the population!
One could almost think this is the wrong approach. I mean really wrong, as in the opposite of a workable idea. Try to imagine how people can live their rural lives in a way that you can stand and you don’t feel the need to control them and eliminate the diversity of human kind.
no sane plant would ever use electrolosys to make hydrogen on a large scale… almost all of it comes from natural gas steam reforming…generally because there’s little use for CO, most of it is intentionally converted into CO2 by water shifting (more hydrogen!) in the same reactor…
Yep electrolysis could be an improvement from an environmental standpoint if the power for the process came from renewable sources. With steam reforming, today’s hydrogen is practically a fossil fuel.
David Sanborn Scott covers the case for hydrogen-powered flight pretty thoroughly in his very earnest book Smelling Land – The Hydrogen Defense Against Climate Catastrophe , especially chapter 40.
He’s very heavily in favour of hydrogen, but does not shy away from discussing the (significant) difficulties of using it. He answers pretty much every argument against hydrogen with a well-researched rebuttal.
I guess it’s completely impossible to synthesize an artificial hydrocarbon fuel from electrical energy. Shouldn’t somebody be working on that.
It’s possible to make fuels from sunlight without converting to electricity first. It’s less efficient than using solar panels to power electrolysis cells, but vastly cheaper, self replicating, and biodegradable.
Those electricity-free methods also can sequester carbon…
Sounds like you’re describing firewood.
And I shall name them “trees” hehe ;)
We do need technical solutions, but at the same time we do need less of nearly everything.
More frugal, more savvy — nothing else will save Spaceship Earth.
You should be writing this in Mandarin and Hindi.
A massive amount of Chinese emissions are directly related to demand for products in the US. Not only is the US a global leader, but it’s people account for an outsized share of greenhouse gasses even before considering US demand for cheap products made in other countries at a significant climate cost. I’d say English is a good choice for language… No, the US isn’t the only country and population that needs to change, but changing before others is a good way to inspire actual change.
It sure is a better use of time than blame shifting at least.
About 25% of China’s emissions are due to exports. The vast majority is still domestic demand, and even if you eliminated exports entirely you’d soon have the same amount due to the growing middle class and increases in living standards.
The third elephant in the room is Africa which is still on an exponential population growth trajectory towards 4.3 billion people by the end of the century, and they too will be wanting the same stuff. The western countries, US, Canada, UK, EU, have a combined population of less than 2 billion and staying steady, while the rest of the world is fast outgrowing us in numbers and in consumption regardless of our actions.
So Greta Thunberg can wear a sack for clothes and throw ashes on herself, but pretty soon she’ll have to start arguing that Africans shouldn’t be allowed to own cars. See how much they care.
Africa is also the prime target for Chinese growth and exploitation. All but one tiny country have already gone for the carrot, and then removed an independent Taiwan from their maps after demands by their new “friends”.
You underestimate the demands of a billion people in a rapidly developing ambitious and militarily growing country.
Less people would be the obvious solution to the problem.
Number one problem all the way down to 10,000. Sooner or later it will get to us and everything else.
You first. ;-)
All the highly developed countries have already halted or reversed their population growth to the point that it’s becoming a problem of sustainability as the proportion of old people is increasing.
The problem now is India, China, and Africa, which are rapidly increasing their populations and energy consumption. In the 1970’s the OECD nations were responsible for 2/3 of world energy consumption. Today our share has shrunk to 1/3 while Asia has increased its share to 1/3 and the rest of the countries take the remaining third. In the next 100 years, Africa is going to grow larger than Asia is today, while Asia is going to at least double, and the world energy consumption and emissions will go up.
If you think some coal country climate deniers in the west are a problem, think about what happens when several billion Asians and Africans go, “We’ve got all this coal and oil and natural gas – why can’t we have all the nice things that you have?”
It’s an uncomfortable thought, but we need fewer humans on the planet.
So, maybe the anti-vaxxers are onto something!
“make headwind” should be “make headway”
Have a look at the work being done with amonia as a hydrogen storage medium. There was an article in the IEEE mag recently on a self contained farming system in the US which manufactured amonia on-site for use as a both a diesel replacement and a fertiliser. If you do a search on amonia you will find a large global consortium looking at the use of amonia as a replacement for diesel & bunker oil for heavy transport & shipping.
The CSIRO in Aus has a project looking at using solar generated amonia as a high density energy transport medium instead of coal and gas however as with most global efforts the commercialisation of the research is sabotaged by the incumbents. The toxic politics of fossil fuels has all but destroyed any semblence of a functional democracy down here.
Virgin has successfully been conducting tests on a renewable bio-kero for use in aviation. In all of these cases the issue is not the suitability of the fuel, the issue is the additional cost added onto usually wafer thin margins.
There are already many potentially successful transition solutions however what all of these existing solutions have to contend with is that the current hydrocarbon based fuels are heavily subsidised in that they carry no cost for the heavy damage that they are inflicting on the ecosystem that we rely on for survival.
As someone currently sitting in a country that is literally alternating between burning to the ground or getting blown away I would hope that we stop fvcking around and get this problem sorted quick smart while we still have a planet left.
Ammonia? Why on earth would they choose ammonia?
It’s cheaper and more efficient to make methane, and has the great property of not killing you horribly if you happen to catch a whiff of it. More direct way to make denser, liquid transport fuels too.
If you really want an efficient, high density energy transport medium, use aluminium. Hard to push through a pipeline very far though.
Other solids fair well.
That was my initial response too until I had a search around and saw the work that has already been carried out. One of the key advantages over methane is transportable energy density at close to ambient temperature & pressure, also there is already a well established infrastructure & set of materials handling practices. It also indicates why hydrocarbons have been so effective to date. Like you it also makes the hairs on the back of the neck stand up ;-)
Page 1 of a google search for “ammonia methane energy density comparison” provides some interesting perspectives from various industry & research groups.
Just fuel the jet turbines with hydrogen instead of messing about with fuel cells.
Derigibles. Lets bring back the Hindenberg!
No, really. We have 100 years more of technology that could prevent fire spreads, and then it could carry its own fuel.
Problem wasn’t the flights. It was the take-offs and landings. Be nice as an air cruise ship.
being lighter then air means you will be moving with it once the wind is too strong, like it or not. Also the cargo capacity sucks ass…there’s a good reason heavier then air aircraft won
This is one area where hydrogen just wont work. Do the math on the energy required of even a short commuter flight and see how big a hydrogen storage unit you will need (as well as flight and crash worthy). Won’t go into how heavy those tanks are currently and how little they can store. And storing the exhaust is going to require tanks, pumps, valves etc that for the most part will sit empty but add tons to the weight. When you design an airframe you are reducing the weight as much as you possibly can.
As well believe it or not the aviation industry is very driven by efficiency improvements and constantly has been. The engines you fly now are much improved over those designs only 10-15 years old. And definitely are not the smokers from the 60’s and 70’s that the media portrays as being in common use. Fuel costs are only going up so the industry looks to get any gains they can by new engines, better aerodynamics and so on. If you can offer even 2-3% fuel cost improvements they would jump and change. When you try to get them to use a fuel with the gallon equivalent cost of around $20 you won’t get very far.
Just fyi I am a pilot, I have designed and built small aircraft, and my company manufactures high efficiency alcohol fuel cells. I worked on a project for a small commuter sized airframe that used a hybrid fuel cell and ultra caps. A poc of the power unit got into the air on a Cessna 150. It had more than enough power and the fuel cell could keep things charged. The fuel mix was just 5% alcohol and water when it hit the fuel cell. Think beer ;-] So even worst case it couldn’t even burn.
Hydrogen cells have a few percent efficiency over other cells but it has so many problems in cost, availability and so on.
Hydrogen storage is trickier than you’d think.
– The Whack A Mole guy.
Can you point to any press releases / technical info about that project or company? Every time I look at non-hydrogen fuel cells again I get overwhelmed by just how much is out there.
The main outstanding issues with fuel cells are:
Cost is high because the cells use special catalysts and other materials such as Platinum, and Nafion for PEM cells, or rare earths and difficult to manufacture ceramic structures for SO cells because the temperatures are too high for regular steel.
Lifespan is low and measured in some hundreds or thousands of hours because PEM cells would require ultra-pure hydrogen and oxygen to avoid fouling the membranes. For direct ethanol/methanol cells, dissolved salt is a problem as well as any side reactions. Any amount of sulfur or carbon monoxide slowly poisons the cell. SO cells are more forgiving because they can burn off small particles of carbon. Gas exchange gets difficult and inefficient when you add filters. The target is to have a fuel cell last for 5,000 hours which is the typical lifetime use in a car.
Power is an issue because of the relatively low power density, and for the fact that fuel cells don’t like to be throttled up and down because it stresses the membranes or produces thermal shocks that degrade the ceramic catalysts; efficiency drops dramatically when you throttle a fuel cell down from its optimum power level, so in practice they’re mostly on/off devices and require some sort of hybrid energy system with capacitors or batteries.
We just need to separate the hot air from the cold, liquefy it, and use rockets to drop it in the Sun. Problem solved!
If you’re already going to be using on-board Hydrogen, why bother with the expensive & heavy fuel cell + electric motor combo when you can just pipe that H2 directly into a high efficiency lightweight gas turbine? H2 fuelled turbines are an old, old idea and have been flown in practice as far back as the ’50’s with conversion of hydrocarbon-fuelled engines: https://history.nasa.gov/SP-4404/ch6-4.htm
Because high temperature combustion of any fuel with air produces oxides of nitrogen which are a pollutant. This is hard to avoid because atmospheric air is mostly nitrogen.
NOx doesn’t form in low pressure combustion until well over 1,500 C and only when you have excess air. At those temperatures and with excess air, the turbines would start to melt. NOx production is suppressed at stoichiometric A/F ratio because combustion of nitrogen draws energy away from the reaction and the reaction balance favors burning the fuel first. Less than 25% excess air starves the reaction of oxygen.
High pressure combustion reduces the energy threshold for NOx formation, which is why diesel engines produce NOx emissions. A diesel engine has a compression ratio up to 23:1 with a turbo to cram the air in at sea level air pressure or slightly above, and since the combustion is confined in a cylinder the peak absolute pressure can reach 180 atmospheres. Diesel engines also run with excess air most of the time.
Meanwhile, a modern jet turbine may have a compression ratio around 16:1. The maximum pressure ratio of the jet engine can be something like 60:1 but the absolute pressure inside the engine is still just 15-16 atmospheres because the intake air pressure at altitude is so low and the combustion process is not confined. There’s not enough pressure and temperature to form significant amounts of NOx.
On the other hand, if you run a turbine very lean (more than 45% excess air), that also suppresses NOx formation by lowering the flame temperature. Some exhaust gas re-circulation can be used in stationary power turbines to dilute the air and again reduce the flame temperature below the point where NOx starts to form.
i love this latest fashion by which people think that progress will solve any problem, just invest massive amounts of someone else’s money in it and presto, miracles will happen, physics be damned.
almost nobody produces new liners from scratch because the money and time required for development and certification is enormous and no private company in the world can afford that. and no, boeing and airbus are no “private companies” and even them avoid developing new airframes if they can, see the 737MAX fiasco for a fresh example.
same goes for engines. engine development and certification costs a TON and requires years, thats why most engines are just refinements of existing engines and not brand new designs.
therefore the only way such wacky idea as a h2-fuelcell powered liner can exist is if certification and safety is totally ignored, as it usually happens when it comes to saving the planet.
and even then the penalization in payload and range will make commercial flight something only the uber rich can afford. assuming those whould give up their Falcon 900 that they operate without feeling any shame.
all those who theorize electric or h2 powered airplanes that are not just silly and expensive “demonstrators” have absolutely no freaking clue of what they are talking about.
those who talk about fuel cells need their head to be checked.
Warming the planet with hydrogen?
Sure, burning hydrogen only produces water vapor. But where on Earth do you get hydrogen? It must be split off from molecules of some other chemical, usually water. This requires energy, energy which probably involved releasing CO2 in it’s production. At the absolute best the only energy you can get from burning hydrogen would be equal to the energy that was spent obtaining it in the first place except thermodynamics tells us that you will never even achieve that.
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