For reference from the UAV industry. The very best lithium ion batteries are about 250Wh/kg but limited in the instantaneous amperage they can put out. High amperage capable batteries are more like 170Wh/kg.
UAV compressed hydrogen tank systems with fuel cells in the 800-1600W range, the full system with tank, fuel cell and a small buffer battery works out to between 800-1200Wh/kg depending on size. Some guys in south Korea recently hovered a large hexacopter for 10.5 hours. The systems I've seen are typically configured for an output voltage equivalent to the float voltage of a 12S lipo.
Diesel fuel, jet a, avgas and other fuels are a whole magnitude more dense in Wh/kg stored than the above-mentioned hydrogen system.
Aside from the (obvious) energy density downside of hydrogen as a fuel, there is another substantial problem.
Hydrogen is challenging/expensive to store/contain. Kind of the direct result of it being the smallest atom we have. Even more important: when it reacts uncontrolled, in particular with oxygen, it does so at a truly frightening speed. Once it goes, good luck doing anything about it.
The fact that this is almost never mentioned in every yet-another-hydrogen-is-going-to-be-our-future-next-year piece, always makes me wonder if that's the result of not-so-honest entrepreneurs trying to lure investors, or that none of these jokers ever talked to any experienced chemist.
This is no attempt to spread FUD regarding hydrogen. It sincerely worries (if not frightens) me, how so many initiatives appear to completely ignore that any volume of hydrogen that is sufficient to power something that can transport humans or cargo, is pretty much inherently a catastrophic disaster in the making. That is, if such a system would ever fail in a way that makes the stored hydrogen react uncontrolled.
Every widely utilized technology is bound to fails, even if only in edge cases, and of course: extra safety margins/features can be added to limit the effects of failures. But with hydrogen that might be a hell of a lot more expensive and/or difficult than most would realize.
So, the way I see this is that we either end up very cost ineffective solutions, or ones that will be far more dangerous than many would ever realize. That is, until something goes terribly wrong, and everyone realizes they have been ignorant and maybe even intentionally fooled by people trying to make money. Reminds me a bit of self-driving cars.
Kerosene burns, hydrogen explodes. And kerosene doesn't actively damage the tank it's stored in, like hydrogen does.[1] Also, while its energy density per kilogram compares favourably to kerosene, its energy density per litre does not.
Hydrogen is a great rocket fuel because its specific impulse is second to none, so why isn't it universally used? Because even by rocket fuel standards it's a bugger to work with.
There are lots of things that react poorly to being set on fire. That doesn't make them all equally dangerous.
Hydrogen embrittlement depends on the type of tank. It does not occur with every material. Look, I'm not saying hydrogen is great and has no problems. I'm saying the problems are not in theory insurmountable. I have elsewhere made the same point as you with regards to mass vs volume. I'm aware of the drawbacks of hydrogen and am actually pessimistic on its use in aviation, but I think it is worth trying out.
Hydrogen is not only in contact with the tank but with other materials en route to the fuel cell as well. And the problems don't need to be insurmountable in theory, they need to actually be solvable and that is a different thing entirely. I'm fine with people trying it out but I'm very skeptical about this ever making it to production. I think this is more of a PR piece than anything substantial.
I don't think hydrogen powered planes will substantially replace normal planes for reasons having to do partially with safety and partially with performance, but I think the engineering problems are surmountable. There are existing prototypes that have flown using hydrogen fuel cells, and the Tu-155 which ran on liquid hydrogen (used as fuel for its jet engines though, not to power fuel cells). So it's not like this stuff doesn't work.
I think you are overestimating the difficulty of dealing with embrittlement. Many materials don't suffer from embrittlement at all, and others (like aluminum) only suffer at high temperatures.
Edit: I also wanted to add to the person who made the claim "kerosene burns, hydrogen explodes" that kerosone can explode too, and it obviously is possible to handle hydrogen in a way that explosion is unlikely or it wouldn't be used as rocket fuel (where it is literally combusted with oxygen... combusted, not exploded). I agree that hydrogen is more dangerous than kerosene, but it's not like kerosene is that safe either and the question is whether you can create good enough processes around the storage and handling of hydrogen to offset the risk.
It's the huge difference in reaction speed that makes all the difference. Even in their gaseous/vaporized forms, conventional (fossil) fuels react comparatively slowly compared to hydrogen, like a sweet retriever puppy compared to a trained dog of war.
It's exactly this difference that makes them relatively safe to use and even still relatively controllable once something goes wrong. With hydrogen, you simply won't get that change. It will be all over in a blink. A very hot and bright one, I might add.
Feel free to believe whatever you want, you have every right. But I'm rather sure that your optimism regarding hydrogen is more rooted in ignorance than in knowledge.
> Feel free to believe whatever you want, you have every right. But I'm rather sure that your optimism regarding hydrogen is more rooted in ignorance than in knowledge.
You have made some great points about hydrogen. But personal insults like that don't help you get your message across.
Yeah, I'm actually more familiar with hydrogen than you think. I'm aware of the problems with reaction speed. One advantage hydrogen has is that it escapes very rapidly from its container and goes pretty much straight up due to how light it is.
I'm actually not as much of an optimist on hydrogen as you seem to think. I think it is unlikely to be used in aviation in any real sense, for a variety of reasons, some having to do with safety, others with performance. However, I think it is worth investigating, and I do not think the problems around it are insurmountable from an engineering perspective.
Thought then I'm sincerely even more surprised you would say that any fuel tank on fire is a (relatively) equal problem.
As for hydrogen rapidly escaping and going straight up because of its low density, those properties I would only consider positive in scenarios where the hydrogen isn't reacting (being on fire, to be more precise). When on fire, quite the opposite. Buildup of heat on the ground might still be less of a problem than with heavier fuels (which indeed is a very real problem with those), but not much advantage of that once everything within a certain radius is reduced to the size of matchsticks by a powerful explosion.
But if you claim to be (some sort of) an expert, I'll believe you. I certainly am not, that much I admit.
I only based my opinion on what I've been told by chemists that I personally trust. They told me rather invariably that the engineering challenges for storing/operating hydrogen are such a bitch, that they are ultimately only a good for when you want something closely resembling a bomb, without actually being one (or just hoping it won't explode before it served its purpose). Like e.g. rocket engines.
I didn't say it would be an equal problem, I said that you will have similar problems if an airplane fuel tank catches fire. The problems you're raising are definitely real problems, I just think they can be designed around.
The engineering problems obviously aren't large enough to prevent something like the Tu-155 from using liquid hydrogen. Whether it can ultimately made as safe as conventional aircraft, I don't know. Maybe not. Either way, I don't think the economics are favorable for hydrogen.
That goes for lots of things including powdered sugar and flour. But that vaporization step usually happens in a relatively controlled environment which makes it manageable.
That particular model? No, I was not aware of it. But that production hydrogen cars exist, yes I did.
However, proof of their existence isn't proof of their safety. I have no doubt that they are (mostly) safe, even in almost every imaginable accident. However, it's the (unforeseen) edge cases that worry me. Not because of how often they might happen, but because of how bad the consequences could be when things go wrong.
It's a real bummer when whole a housing block gets wiped of the map, because one eccentric/rich guy just had to do something "for the environment" (#sarcasm).
From what I read, this car has storage capacity of 5 kg of pressurized hydrogen. I've seen similar storage tanks, and I have been amazed about how resistant they are to puncturing and tearing forces. Unlikely that any direct impact collusion would destroy one of these. But then there is always some corner case that it wasn't designed for. I certainly would not like to be even remotely around it, when 5 kg of pressurized hydrogen goes up in flames.
As hopefully every engineer knows, catastrophic failure is almost always a cascade of smaller compounding failures. Disrupt that chain-reaction and a catastrophe is usually averted.
However, with hydrogen the opportunity/window for that is often extremely short, with extreme consequences as a result. Not quite what you might call an optimal combination of factors.
Technically we could drive cars on nuclear reactors.
One of the things that really worries me about the concept of mass market hydrogen cars. I'm talking in the millions of units. Ordinary consumers do all sorts of slightly dangerous, ignorant things with their vehicles. Including neglecting maintenance.
I am not sure I want to see the average untrained person handling a precision refueling apparatus that connects to a tank at 250 to 700 bar pressure. It's a lot more complicated and technical of an interconnect to refuel compared to just sticking a petrol station nozzle into a tank and pumping.
I don't think a system that requires a professional refueler staff person at every hydrogen fueling station is a good idea either.
That is what worries me too. Not so much the current state of affairs, in which maybe several thousand to tens of thousands units driving around. But as the production scale goes up, so do the chances of hitting those unforeseen (or willfully accepted as "cheaper" to mitigate with financial compensations, because that is how the industry functions) corner cases where things will go wrong.
Substantially more than 5kg of hydrogen went up in flames with the Hindenburg, but I don’t think anything was wiped off the map there.
Do you have any reference to the actual danger of stored hydrogen?
Actually liquid H2 has energy density of 39 kWh/kg, where common CH fuels are around 12-13 kWh/kg. So about 3x more energy per kg then conventional fuels.
Note that H₂ boils around 20-30K (depending on pressure). Once you take into account the weight of the insulated tanks, liquid H₂ is going to have much worse energy density.
Liquid storage I believe typically gets up to about 20wt%, so you're talking around 7.8kWh/kg. Compressed storage is around 6–10wt%, so up to 3.9kWh/kg.
Hydrogen becomes significantly more efficient as you scale the tank. Don’t forget many rockets use Hydrogen over Jet-A and they really care about weight.
Rockets use liquid hydrogen, which is a pain to work with, but not too bad if you can fuel up and launch relatively quickly before too much boils off. The real reason rockets use hydrogen is because Hydrogen and Oxygen gives the highest specific impulse of any chemical rocket. You really don't care about specific impulse in a jet aircraft, and you really don't want the fuel boiling off before the end of your 12-hour flight.
Also, if you're thinking of pressurized gaseous hydrogen instead of liquid hydrogen, then the tanks get really heavy because high pressure tanks don't scale well (unlike low pressure liquid tanks which do). Hoop stress is proportional to diameter, which means tank wall thickness needs to grow with diameter too. https://www.engineersedge.com/material_science/hoop-stress.h...
Boiling off is a function of surface area which means it scales really well with volume. Rockets have issues because they don’t want to bleed off hydrogen on a launch pad or use significant insulation, but aircraft can just feet that to the APU or engines in flight. You will want to drain hydrogen for maintenance etc, but that’s not a significant issue.
Some rockets, and generally on lower-thrust high efficiency upper stages. Hydrogen has a low energy density in terms of volume. It requires larger tanks and so is rarely used to get off the pad.
RP1 is effectively a purer version of Jet-A, and is a very common propellant. I'd say it's more popular than hydrogen, but I'm not sure I can back that statement up. It's what fuels the Falcon 9 lower and upper stages.
> UAV compressed hydrogen tank systems with fuel cells in the 800-1600W range
They didn't say how they would be using the hydrogen. I haven't been able to find it again, I did read about an article about a long endurance (days), high flying plane. It was powered by hydrogen. It burnt it. As I recall it was in an ICE, but at 50% efficiency using it as jet engine fuel isn't such a bad idea. It has an energy density of 120 MJ/kg, 3 times as much as normal fuels so it makes sense either way, if you can contain it.
In other news, the country where I live (Australia, 6th largest exporter in 2019) is contemplating exporting hydrogen. Why? Because if renewable power continues on its current price trend it will be cheaper to produce hydrogen than it is to mine the natural gas we currently export. Again, I presume no fancy technology - it will be burnt just like the natural gas is.
There is more than one south Korean company working on combined packages of lightweight hydrogen tanks and fuel cell power systems. And several American companies.
If my understanding is correct, the goal is to reduce aviation effect on climate change.
There is an ongoing project [1] by US NAVY to turn seawater into jet fuel. This way we would not need to burn fossil fuels and would not need to throw away much of existing aviation technology.
Water is free [1], Carbon Dioxide is free [2]. Energy is never free.
You need some big solar panels or a nuclear reactor to get the energy. (Can you put a wind turbine in a ship?) (The usual trick of burning fuel to produce energy is not a good idea here.) So this kind of process should not be interpreted as "water -> fuel" but like "energy -> fuel".
It can be useful to store energy for a while, or producing fuel using a nuclear reactor in the carrier and using the fuel in the planes. (I'm not sure that this is economical or tactically a good idea.)
If the idea is to produce the fuel on land, it is much more efficient to sell the energy and buy fuel. The energy you sell will cause a electric plant that use carbon to close and the net effect will be bigger reduction of the CO2 level.
From the article:
> Laboratory team led by Heather Willauer announced it had used a catalytic converter to extract carbon dioxide and hydrogen from seawater and then converted the gases into liquid hydrocarbons at a 92 percent efficiency rate.
I really doubt this. Organic reactions have a horrible low efficiency, specially the ones that create complex molecules using simple ones. (Perhaps the 92% efficiency is counting how many of the CO2 are converted, but the most important part of this reaction is the energy. If it convert the 92% of the CO2, but it stores only the 1% of the energy, it is very wasteful.)
[1] Processing water to avoid the problems with salt and tartar may be a big problem, so it may not be so easy.
[2] But the concentration is usually low, that is generally bad for fast and efficient reactions.
In terms of energy, it's not a contest and it's not a hangup. Carriers are already powered by nuclear reactors. They have about 1500MW of steam power available as a matter of course. Compare to 25MW if you paved the flight surfaces with solar panels and parked it at the equator on a sunny day with perfectly calm seas and measured at noon. Unlike solar in this example, the nuclear design is not bumping up against physical constraints and could be scaled up quite dramatically if there was a compelling reason to do so. Fuel production would be a compelling reason.
The chemistry and chemical engineering problems you point out are the major hangups.
Sayong they are converting water to fuel focuses on the wrong (least important) part of it. The point is that it fixes CO2 from the air into hydrocarbon fuels via generating carbon monoxide and using the Fisher troph process to assemble fuel molecules. This is really just congealing electrical energy into hydrocarbon fuel. For now in the lab, you still get that energy from fossil fuels. Presumably in the future you would use this process to congeal extra solar or wind energy into fuel rather than keep them stored in batteries
In this particular case, they are planning to take energy from carrier's nuclear power plant.
More generally, either hydrogen or fuel synthesis requires energy to come from somewhere; In this regard it is no different than re-building airplanes to use hydrogen, as the original article suggests.
The point is that we might have better chances synthesising fuels usable in existing planes, versus re-building majority of aviation to use hydrogen.
Hydrogen is expensive to produce, cumbersome and dangerous to store and handle. How will that be competitive with traditional jet fuel?
Jet fuel is safe to handle, the infrastructure is there, it doesn’t go all Hindenburg in a crash, and it doesn’t require new engines.
What we need in the next decade is a better jet fuel.
If commercial flights all used 50/50 renewable fuel that would cut greenhouse emissions in half. Providing that much biofuel without disrupting food production or fresh water supply will require a moonshot effort but it still seems like a simple obstacle compared to replacing fleets with electric or hydrogen powered aircraft.
> If commercial flights all used 50/50 renewable fuel that would cut greenhouse emissions in half.
Airline emissions aren't that bad compared with everything else, but they aren't being decarbonised at the same rate like everything else, and on top of that they are growing dramatically.
In 2019 there were 4.5b passengers globally. In 2006 there were 2.25 passengers globally, so doubled in 13 years. Planes are slightly more efficient now, but there's a long tail of less efficient planes.
Moving to 50:50 biofuel may save a decade of growth, but it's not a silver bullet.
We could also ramp up nuclear power production and build hyrdocarbons from water and CO2. Lots of things become more practical with cheap, abundant power (assuming we can get that from nuclear).
That could eventually be true, but currently under 5% of hydrogen is produced by electrolysis or biomass gasification, the rest is all processing of fossil fuels.
Hydrogen's energy-density makes it by far the best possible fuel for aviation. Improvements in aerogel manufacturing are making liquid-hydrogen tanks a practical prospect. LH2 is not mass-dense enough to fit in the wing tanks of existing airframes, but at least the LH2 tanks won't need to be pressure vessels.
Production of LH2 from cheap solar- and wind-generated electric power and water, right at the airport, will make aviation the most practical place to start using hydrogen as a fuel. Maybe auxiliary LOX tankage could help reach cruise altitude more quickly, or enable flying higher, so as not to waste the oxygen by-product.
Hydrogen only has a high energy density by weight, but by volume it's actually quite low compared to other liquid fuels. Then you have all the problems with handling liquid hydrogen, insulation needed, all sorts of additional functions are required of the storage system compared to jet fuel. For example, icing would probably be a problem if the wing tanks are full of liquid hydrogen!
Ice on the outside isn't a problem for the hydrogen. It's the other way round. The weight calculations have to include enough insulation on the tanks to prevent rain from freezing to the wings.
Liquid hydrogen tanks are definitely a different problem, but I don't know if "orders of magnitude safer" is necessarily true. Many spacecraft have run into problems involving liquid hydrogen storage for a variety of reasons:
- Liquid hydrogen is so cold that many metals weaken
- Exposure to hydrogen itself weakens many metals (hydrogen embrittlement)
- Liquid hydrogen expands rapidly if exposed to heat, so venting is needed
- Hydrogen leaks through the smallest of seams
Now imagine trying to build a tank that prevents all that from happening, and it has to be lightweight for usage on spacecraft / aircraft.
The Hindenberg blew up because there was a bomb on board. No aircraft design is noted for resistance to onboard explosives.
Furthermore, the flames seen in the film were from kerosine fuel. All the hydrogen released went up, up, up. It is quite difficult to ignite hydrogen at atmospheric pressure; it requires oxygen mixed in a narrow range of partial pressures.
I feel more guilty about our usage of non-renewable, GHG-generating power sources like coal or natural gas power plants, and about driving around in my car (even though it’s electric).
Aviation accounts for just 2% of CO2 emissions. While it’s good that Airbus is considering alternative, greener fuels, because aviation will continue to grow, there are larger determinants of GHG emissions and warming.
Also, how you even certify use of hydrogen on an aircraft will be a challenge. The current design for fuel has been well-understood for seventy-five years now, and like the rest of aviation some improvements have unfortunately but unavoidably come from tragedy (see TWA 800). You can throw a match into Jet-A and it won’t catch fire. Throw a match into a flask of hydrogen and you have a fire or explosion.
I've noticed that a lot of the discussion around environmentalism is focused as if the bad decision-making is happening at the consumer level. The pervasive belief that A: electric cars directly reduce your personal carbon footprint (they do, but the substantiality of that depends on where you live) and B: travel is a major drain on the environment are very suspicious to me. These are pervasive beliefs among environmentalists. Meanwhile very little attention is paid to corporate and nation level changes. The best thing you can do for the environment is vote. This feels counterproductive but it's entirely true.
In addition, it seems to me that the discussion around nation level changes has become focused on a developed nations vs developing nations issue, when in reality it's all of our issues.
I do agree, and take it a bit further: I feel that one of the greatest modern tricks that have been played on us is to shift attention away from the actual culprits and make us believe that it is us, at the lowest levels, who need to make the changes and fix the environment. Things like flight shaming and straws stand out as prominent examples and this could very well be due to the tangibility of the actions. When they avoid a flight and take public transport, or use a metal straw, they can feel like they are doing something. But the impact is miniscule compared to what they could be doing which is enacting a policy change at higher levels, changes which will have an impact for years to come.
This 'attention shift', it's similar to the way the plastic/oil industry successfully instilled recycling as a way to get us thinking we're doing something useful, while the larger goal was to keep plastic bans at bay [1]
This trick plays itself out in other spheres; recently in the UK we would have people "clapping for the NHS". They would stand outside their doors and clap or bang pots/pans together. Very few of us wrote to our MPs asking for better working conditions and better pay. Anyway, just last week, our government voted against protecting the NHS from a post-Brexit trade deal.
The most efficient solution is ridiculously simple - put a tax on the emission of pollution. Couple it with a corresponding tax reduction on productive behavior.
This is based on the blindingly obvious maxim that if you want more of something, subsidize it. If you want less, tax it.
And by taxing pollution instead of regulating it, you generate revenue for the government.
In the us people riot if police kill an unarmed black.
People in the us accept that the price of fuel goes up and down but they are the only ones. In other countries people riot when the cost of fuel goes up.
Many people have a lot of fear that tradable emission permits are an Enron-style scam that will suck money out of our pockets into somebody's pocket who will recycle 1% of profits back to politicians to maintain their privilege.
What we need to is either ban certain uses of fossil fuels or introduce an energy source that is so superior that people don't want to use fossil fuels. The latter is hard but doesn't violate the laws of physics, but any other kind of Collective action on climate violates the laws of social physics which are absolute for N > 10^9.
The protests happen in part because the demonstrators do not trust the government to spend the money well. They are afraid that they will distribute it to the "usual few" or "subsidize the lazy ones".
Distributing the tariffs equitably among the population would take that stigma away. This would encourage those tariffs that are so necessary for us to comply with the Paris agreement.
People don't like paying taxes and they also don't like their taxes being wasted. If the tax is revenue neutral (refund total co2 tax revenue divided by number of tax payers) there is no problem in theory but people still hate taxes.
I go a step further and say for consumer stuff, put a stiff excise tax on things that emit pollution at the point of sale. Don't apply a $60/ton carbon tax on gasoline. Put a $100/ton excise tax on new cars. Use the cash flow to buy back older cars.
When it comes to industrial stuff, that's what you just work with industry to generate mandates that everyone has to follow. Manufacturing managers I talk to say they don't mind mandates. They just don't want to the be the sucker. As in Gallant installs $5 worth of emissions controls. Gooffus ships the factory to Indonesia and bribes government officials to look the other way.
Only source of CO2 that has relatively grown for the past two decades.
> they do, but the substantiality of that depends on where you live
This is true but misleading: yes if your electricity is produced by coal plants electric cars are just slightly better CO2-wise (but cleaner on NOx and other sources of pollution), but the idea is to move away from coal so that running your EV become cleaner over time. (1)
A striking example is the UK, this chart tells the story of coal to renewables:
General consumption drives the need for heavy industries that contribute the most to pollution, so it's indirect but still the consumer at the helm.
However, I totally agree that the focus should be on those heavy polluting industries. I don't believe it's evil for humans to want to live the lives they do, with the technology we've created, and I also don't think we can change enough people to ever make a dent in those consumption requirements. Better to fix the issue more efficiently, at the source of the pollution, by switching heavily polluting industry out for greener alternatives, as the input into the consumption machine.
At least I think we agree the whole solve the problem by nudging consumers personal choices but otherise slap them silly when they make or worse previously made what or now bad decisions is kinda terrible. See imposing a stiff carbon tax on someone filling up their 15 year old car.
The size of needed changes and consumers limited agency makes anything but coordinated society wide action a worthless endeavor.
Aviation is responsible for 2% of carbon emissions but was growing at 4% per year.
Aviation is responsible for the mass tourism that drives people out of cities to make way for airbnb's. This increases their commute. It also increases real estate speculation, i.e. more construction of houses (cement alone accounts for another 2% of emissions).
We cannot take a reductionist view of the problem. Mass tourism was one of the biggest environmental problems and was based on aviation.
Travelling by air is a privilege that only a small percentage of the population has access to. If everyone did that we would quickly exhaust our carbon budget.
It is funny that people in the aviation business don't treat it as if it was a growth business. That is why Boeing feels entitled to keep making a 50 year old airframe forever. You couldn't do that if you were making cars.
When it comes to environmental consequences aviation is a growth business, the most important thing we can do is address the 737-class airplanes that people ride in, not the widebody airplanes that are advertised in magazines. Too often ideas like blended wing body, hybrid, and hydrogen are used as excuses to delay a 737 replacement. We've been watching this movie for decades but these is enough $$$ going to the media and politicians and nothing will replace the 737 until the Chinese do it with to the C919 and then all the people who brought you this disaster will say they were blindsided. They get blindsided every time because that's what they do.
Because fire consumes oxygen (which you have an enormous supply of) that people need to breathe as well as the airframe/wings you need to stay in the air and the landing gear you need to safely get back on the ground.
> Aviation accounts for just 2% of CO2 emissions. While it’s good that Airbus is considering alternative, greener fuels, because aviation will continue to grow, there are larger determinants of GHG emissions and warming.
Agreed. This is why, despite being an active member in the sustainable movement for nearly 18 years now, I've never once felt 'ashamed' due to my travels all over the World and will continue to do so. The model shows that unsustainable living habits, particularly those of waste and uncaptured value due to loss in these network,s are the real glut of not just CO2 emissions, but also of CH4 and other more harmful GH gasses.
If anything Travel, not to be mistaken with tourism, can open your eyes to seeing your Fellow Human as you see yourself as you interact and briefly and live as he does and in turn walk away with a Global sense of Community and an understanding that cannot be conveyed in books, TV or movies. I think it's why despite my 'radical thinking' I sincerely feel that the ICE based model for airplanes, and rockets will likely always remain. We should strive for constant refinement, not scrapping it since it accounts for so little of total GH emissions and can have a high ROI.
> These are pervasive beliefs among environmentalists. Meanwhile very little attention is paid to corporate and nation level changes.
No, its just not enforced up on by Nation States, as they often have strong incentives to keep things as they are, the environmentalists (I'm one) have been pushing for corporations to be held accountable for eco-cide [1], and be held accountable for all the costs it has and will incur, which in turn could help fund the remediation of those sites.
> The best thing you can do for the environment is vote. This feels counterproductive but it's entirely true.
No, entirely false, for the reasons listed above. The best you can do is think Globally and act locally about the problem. That is begin to get active in these matters in your community and share your ideas and build a collective of people driven to see these goals get accomplished in real-time; the State will not do it for you, and waiting and relying on them to do so is how we got to this point and why its so wide spread. People are still surprised when they're expected to use their corrupt Legal system and expect another result?! Your diffusion of PERSONAL responsibility to this apparatus is the real problem, not what specious reasoning or beliefs some 'environmentalists' may or may not have or use.
Voting gives you the illusion you're doing something, when you really aren't and are only really validating a flawed concept with your continual participation, and the idea of it ever really making any difference is where you see the divide between people who actually do, and those that only talk about it. The former being where most people remain to this day on the matter(s) even as the problems continue to compound.
The vast majority of the existing hydrogen pipeline is sourced from fossil fuels, so that's more of a greenwashing thing than actual environmental impact improvements.
I don’t think that’s a strong argument against hydrogen. At the moment, the vast majority of everything we build uses fossil fuels, including most batteries. Most batteries are even charged using power from fossil fuels.
What matters is whether hydrogen tanks can be a cheaper or better approach to storing and transporting lots of energy than competing technologies.
Proponents of using hydrogen say existing electricity infrastructure has way too little capacity making hydrogen, which can be pumped through existing gas lines, an attractive approach alongside electricity for transporting power. That makes it more attractive for storage, too.
It is sorta getting out there. Eg our corporate booking portal told you price and carbon emission so it was at least sorta in your face every time you fly
Stupid choice. Combine electrolyzed hydrogen with CO2 Instead to produce methane. A safer and easier fuel to handle and use. SpaceX is already developing their rockets to use it.
Hydrogen is too much of a trouble fuel with no infrastructure in place to handle.
The problem is of course where to get the CO2 from. It should be gotten from some kind of carbon capture setup. Ideally from biomass power plants.
As long as your fuel tank doesn't like it's fine. Burnt methane is back to CO2.
What this whole thread boils down to is we need a huge amount of nuclear power, after which rather than worrying about all 3 of "safe", "dense", "efficient", we can just worry about the first 2.
Seriously, if it takes 1000x the energy from nuclear power to fix enough C02 to make conventional jet fuel from the air, that is fine. That's something we can optimize on a leisurely basis when we are not worrying about global warming.
I always wonder if hydrogen is a side-step without any real practical use or will somehow create a niche where the high-density requirements of long range travel are needed. I.e. airplanes and cargo ships.
Hydrogen is awful to store and has no existing infrastructure around it, and you only get efficiency gains if you use fuel cells, otherwise it's back to Carnot's law.
Compare this to synthetic biofuels. They are already the market, as an example I can go fill up my diesel car right now with it, certified to work by the manufacturer, and can be transported and used by existing infrastructure.
Why isn't this talked about more? Are the land usage requirements making it unfeasible for a global switchover in the aviation and maritime industries requiring converting CO2 from the air making it much more expensive? Or is it simply not flashy enough?
If you have tons of near free energy, and hydrogen, making other synthetic fuels, which are way more storable is not a problem, a ton of other avenues will open in chemical industry for "direct synthesis"
Fuel cells can also use synthetic fuels, including hydrocarbons, and ammonia.
> Hydrogen is awful to store and has no existing infrastructure around it, and you only get efficiency gains if you use fuel cells, otherwise it's back to Carnot's law.
Plus the hydrogen production pipeline is mostly from hydrocarbon so it's no gain at all. AFAIK hydrolysis is currently rather expensive and mostly for situations where you need very pure hydrogen (e.g. scientific application).
Part of the discussion in the UK at the moment is around the feasibility of reusing existing natural gas infrastructure (good luck with that) and building explicitly green hydrogen plants as opposed to generating from hydrocarbons.
The problem is the scale you'd need to make a dent. It's being proposed as a serious solution to road and rail transport hydrocarbon use, and the power requirements are bigger than anyone I've seen addressing. The last-mile distribution problem is also not inconsiderable, but it pales in comparison to having to copy and paste a chunk of our existing renewable energy fleet.
It has a higher energy density but not "very high".
Lithium-ion tops out around 2.4 MJ/L, LOH 8~10. Maybe one order of magnitude difference when you use less dense li-ion. Plus that energy density of LOH doesn't take in account the absolute hell that it is to keep stored. Fossil fuels are in the mid-30s by comparison.
What LOH does have compared to batteries and even fossil fuels is very high specific energy (energy per kg), it's about triple fossil fuels and a good 2 orders of magnitude better than li-ion. That's why it's been used a lot in rocketry, where mass is a much bigger concern than volume.
There is two densities to care about when talking about energy sources. Energy density per volume unit and energy density per mass unit.
Hydrogen has a very high energy density per mass unit (the highest of the chemical reaction energy sources). But lower energy density per volume than Li.
The two figures matter for different use cases, cargo-ships and aviation want to optimize for energy density per mass, while small passenger transport (e.g. scooters, cars...) wants to optimize for energy density per volume.
This is nonsense. If they want to be net zero emissions, they can use synthetic jet fuel produced from sea water. The US Navy has studied the topic and concluded they can produce such fuel at a cost of $3-6 per gallon [1].
Synfuels are made using H2 and CO2. In practice, they're just H2 with more steps. So while you can use them, it ends up being a trade-off between cost and how much you really need synfuels.
Yes, but synfuels are a drop in replacement of the current fuels, and they are net zero emissions. Hydrogen is nasty. Really, really nasty: in liquid form it can only be stored at impossibly low temperatures, it has a very low density (about 13 times less dense than water), it leaks easily, it creates frost (remember the o-rings from the doomed space shuttle). Building a new airplane is difficult enough, building that burns hydrogen instead of regular jet fuel is an enormous engineering challenge. The chance of us ever seeing a hydrogen-based airplane is exactly zero.
Synfuels are not a drop-in replacement. Jet-A has exacting standards, and it would be a serious chemistry challenge for synfuels to match Jet-A exactly. Most likely it would be possible but very costly.
Most of that stuff is engineering superstition at this point. Most problems regarding hydrogen were solved decades ago. BMW actually made a LH2 powered car and had no big problems (except limited range).
Frankly, you're just incredibly out of touch. We already are seeing H2 powered planes now, and a commercial jetliner powered by H2 should happen by 2030 or so. This very thread is about Airbus planning on building one.
At least an airplane can land without power, though the idea of a hydrogen aircraft (with the hydrogen stored in the wings if it's anything like conventional aircraft) catching on fire is pretty terrifying.
There are many aviation disasters caused directly or indirectly by the fuel catching fire.
Such as the horrific SST crash.
The idea that jet fuel is somehow safe is just a terrible misjudgment of the situation. What we have learned over time is how to handle it safely - but it is NEVER safe and it DOES burn. Another way to set it merrily burning is to scrape an airliner along the runway, or have the airliner hit any sort of obstacle, or for the fuel to leak onto hot engine parts, and on and on.
> The idea that jet fuel is somehow safe is just a terrible misjudgment of the situation.
Surely if that's your benchmark then nothing is safe (with enough effort, few things don't burn), and the point is really rather the safety margin, which is significantly larger for fossil fuels than for LOH, therefore making them much safer than LOH? There's a reason why we prefer dynamite to liquid nitroglycerin, even though both do, in fact, explode.
A lot of aviation accidents result in devastating fire. A fire in the air can destroy the airplane in a minute or two. If there's a ground accident, there's a darn good reason why the FAA requires evacuations within 90 seconds or something like that. Fire is the reason.
As I said, jet fuel is NOT safe. What we do is try to safely handle it.
For example, nobody in the industry is going to allow a lit cigarette anywhere near an airplane.
We have a lot of experience with jet fuel fires and have learned how they burn, how they start, how to fight them, and how to prevent them. We have very little experience with hydrogen fires. They may be worse, they may be better. We don't know.
The concept of biofuels is a closed carbon cycle (more closed but not ideal). Plants with the aid of the sun scrub CO2 from the atmosphere, you make the plants into biofuel and then burn that back into CO2 in the atmosphere.
As opposed to digging it out of the ground where it's happy staying outside of our environmental system.
There is no way you'd get me on a hydrogen powered aircraft. Hydrogen is a tricky substance to handle at the best of times, it explodes with the least provocation and has a lot of effect on the materials that package it. By then I hope my flying days are over but just in case they aren't that is something that would have an immediate impact on my decision to travel or not.
I assume this is fear of a Hindenburg type incident? I would assume that these aircraft would be carrying much less hydrogen, since it's used only for propulsion, not as a lighter than air filling. But, that's only speculation. Anybody have facts to inform this?
Hydrogen needs to be treated with the proper respect at all times when it isn't safely bound to something else. It really doesn't take much to set it off. That the Hindenburg ever got off the ground is what is impressive about it, the amount of care that went into ensuring that a static charge could never reach the reservoir must have been massive.
Hydrogen plants have exploded in the past as well. Given aircrafts' tendency to build up static charges and to be hit by lightning I would not bet on that particular technology to work out.
The Hindenburg was - and that a pretty weird thing to write - about as good as it gets for an accident like that. Only about 1/3rd of the people on board died and it happened during a time when the aircraft was already fairly low (during the last stage of mooring). Had this happened at altitude likely all hands would have been lost.
The article ends by pointing out the author has no data on whether hydrogen cars are more dangerous than others. Nobody would argue hydrogen can't be dangerous. The question is, is it more dangerous than jet fuel?
Jet fuel is closer to diesel than to gasoline the activation energy for jet fuel is much higher than for hydrogen, its molecules are larger so it can be contained safer and with less chance of leaks. So the answer is yes, it very likely is much more dangerous than jet fuel.
In my city there is a bus using a hydrogen fuel cell.
I noticed it produced interference in my bluetooth headset with noise reduction (I can hear the engine in my headset), i'm curious if it will interfer with plane sensors.
This is maybe an inverter. But definitely not the fuel cell itself. The fuel cell will produce pure DC current which won't interfere with anything. However, e.g. a DC/DC inverter that steps up the voltage might not be well shielded.
I know there were some test engines, but none every flew to my knowledge. The problem is they spit out radioactive matter over everything they fly over and expose the occupants to a lot of radiation (since you can only contain the radiation so much when you have weight limits to make). They are badass though.
UAV compressed hydrogen tank systems with fuel cells in the 800-1600W range, the full system with tank, fuel cell and a small buffer battery works out to between 800-1200Wh/kg depending on size. Some guys in south Korea recently hovered a large hexacopter for 10.5 hours. The systems I've seen are typically configured for an output voltage equivalent to the float voltage of a 12S lipo.
Diesel fuel, jet a, avgas and other fuels are a whole magnitude more dense in Wh/kg stored than the above-mentioned hydrogen system.