A problem might be that the H2 molecule is much smaller than the ones of a scent, so tiny leaks will favor the hydrogen. 
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Oh!!! Of course.
ETA - should the hydrogen discussion get broken out? (I’m afraid to try it right now since I’m on mobile)
Others have already weighed in on some of the logistical drawbacks that have so far kept hydrogen from going mainstream, and I’m personally not very bullish on it mostly because I think if it was ever going to have its big moment that probably would have happened by now. Millions of electric car owners are now used to charging their vehicles at home or at work, so going back to requiring regular trips to filling stations seems like a big step backwards in convenience. Plus all the industry momentum and majority of investment is going towards battery vehicles so I don’t expect the industry to make sudden shifts towards a technology that requires a completely new infrastructure to be built up.
If lithium shortages do get critical and the new mines coming online can’t meet demand, there are still other battery chemistries available. Sodium-ion batteries (which are made with much more abundant and cheap materials) are starting to go into commercial production and while their energy density is a bit lower than lithium it’s reaching the same general ballpark and it is more than enough for some vehicle applications.
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The idea has not been totally abandoned. I wish I could find it now, but my view was based on an article where some engineer broke down all the bonuses hydrogen fuel offered versus other types of batteries.
I’m no chemist or engineer, so I’m relying on you and others here (as well as whatever else I read online) to offer insight. I’m not married to the idea of hydrogen, but I’m not ready to completely dismiss it either. (And I appreciate all the debate here, it’s very enlightening.)
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I don’t mean to suggest that it won’t have any role in the future of transportation, but it’s hard for me to envision the majority of cars ever running on hydrogen. Even the article that you linked to includes the following caveat:
That said, maybe there is some market for the specific type of hybrid vehicle that Honda plans to build. It uses batteries (and didn’t say if they’re lithium or not) for day-to-day driving and only uses the hydrogen fuel cell in order to quickly refuel when needed to extend range on longer trips.
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The one niche where hydrogen is likely to find a home is air travel. Batteries are too damned heavy for airplanes and electric planes on lithium batteries will likely never go farther than regional puddle jumpers. There are some startups attempting this now for routes currently served by turboprops, but they are at the extreme limit there and it will never scale to transcontinental or intercontinental flight.
Hydrogen may be the only way to decarbonize air travel, and it may be the last domino to fall. Replacing Jet A will be hard.
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As long as you’ve got a clean energy source to power the reaction there’s always the option of synthesizing jet fuel out of CO2 from the air, and among other advantages it doesn’t require major changes to existing aircraft.
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People keep throwing that phrase around, but it’s not really apropos here. The issue is always that large companies don’t pivot well. This is why they often don’t survive technology paradigm shifts. I suppose you could call that “poor management”, but that’s a bit like calling the Titanic poorly engineered because it couldn’t swing the bow quickly enough to avoid the iceberg. Perhaps true as far as it goes, but not really a fair criticism. No big ships turn all that well, and nor do big companies. They are engineered to go a certain way as quickly as possible for as long as possible. They are not maneuverable and sometimes get stuck sideways in a canal.
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One other thing on hydrogen vs lithium. They are both a form of energy storage, so an important measure is RTE - round trip efficiency. Let’s say you’re starting with solar, looking to store energy during the solar duck curve hours about 12pm in California.
If you charge a lithium battery you’ll get a RTE of 85% in the real world. Meanwhile, a stationary containerized hydrogen system is less than 50%. It also has a storage density in a matrix that is 1/3 of NMC lithium batteries. When I talked to the containerized H2 people at SPI they were not hopeful of electrolysis getting better any time soon… and they were thinking H2 could become deeper multiday storage for microgrids where cost is not an issue and a propane generator is unacceptable.
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If you charge a lithium battery you’ll get a RTE of 85% in the real world. Meanwhile, a stationary containerized hydrogen system is less than 50%.
Yep. I worked for a company that was developing H2 for energy storage. I would love to see H2 succeed and make a positive difference. But with H2, there is a vast gulf between what I want and what’s realistic. The baked-in headwinds of chemistry and thermodynamics are strong.
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Electrolyzers to split water back into H2 and O2 aren’t cheap. This can probably be fixed with a manufacturing swing, much like happened with solar panels.
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Storage problems associated with liquification or high-pressure gas storage are brutal. There’s been a lot of work on a third method, which is gas adsorbtion - basically a big metal sponge that hydrogen molecules like to stick to under bbq-gas pressure (30-ish bar). This solves a lot of storage issues.
Those are the “foreseeably solvable this decade” problems. Now for the “no solution in sight” problems.
- Transportation
In liquid form, H2 will boil to gas at 33 Kelvin, no matter what pressure you squeeze it (i.e. “critical temperature”). 33 K is insanely cold, and makes liquid natural gas (LNG) look really easy by comparison. LNG is hard to get right.
In gas form, the 700 bar cylinders are expensive, heavy, and have a lot of paperwork.
And if you’re adsorbing the gas onto a porous substrate (see above), the gas cylinder + adsorbent will weigh almost as much as a solid tube of steel. You can only load so many before the truck springs break or the boat sinks. The tonnage of steel you’re transporting dwarfs the tonnage of H2.
Natural gas pipelines cannot be dual-purposed to carry hydrogen. The leak situation is different, the compressor needs are different, and the metal embrittlement is a completely different problem with hydrogen, one we never had to consider for natural gas. If you want hydrogen to travel by pipeline, you need dedicated hydrogen pipeline infrastructure.
- Leak-proofing.
As stated above, it’s a tiny tiny molecule that can squeeze into the intermolecular sites of solid steel.
- Odourless, colourless, and burns with a nearly-invisible flame.
Imagine if somewhere near you is a hydrogen fire, and you’d like to run away from it. I’m not sure what I’d do, apart from take shallow breaths and walk with my hands sweeping in front of me, seeing whether they burn. It’s a goddam nightmare once a fire starts, and if you’ve stored it as a high-pressure gas or in liquid form, it’ll be a spectacular fire.
- Explosive in low concentrations.
A bit worse than natural gas. Hydrogen has a lower explosive limit of 4%, methane has 5%. That 1% is a bigger difference than it sounds.
- Low round-trip efficiency, mentioned above.
40% efficiency is realistic, 50% is practically possible, with a lot of battery-juggling to keep the fuel cell in its optimum range. 60% is lab-possible, especially if you do some creative accounting by using waste heat to warm the room and call it “output”. By contrast, a battery will get you 85% without breaking a sweat. The hydrogen efficiencies are a rock-solid limit of applied thermodynamics, and will be as long as we are using engines or fuel cells to convert hydrogen gas into mechanical power or electricity.
- Coupled with the low efficiency - lots of moving parts.
There’s plenty to break, leak, and wear out. Even without a disastrous flammable gas leak, there’s lots of room for fuel cells wearing out, cooling water leaks and pump failures (anyone with a car knows the deal there), electrolyzers corroding, etc. A battery requires a lot less attention.
Does H2 have any future as a fuel? Absolutely - NASA prefers it. By mass, it’s the most efficient rocket fuel we have. It’s also a pain to deal with, but NASA are well-versed in LH2 issues and are pretty good at fixing them by now.
Outside rocketry, if adsorbtion storage is production-ready before sodium batteries I can imagine some fixed storage / surplus renewable power storage. In that scenario, the electrolyzer / storage / fuel cell sit on the grid and don’t go anywhere. The megawatts (i.e. maximum power output) are expensive in this case, but the megawatt-hours (hours of production that can be stored) are cheap.
I’m pretty bearish on H2 for aviation, because it’s either too damn cold or the containers are too damn heavy - look at how many launch delays NASA has because of LH2 issues. There might be a way (lightweight adsorbtion substrate?), but it’s outside my imagination. Granted, lots of things that happened were outside my imagination, so…
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Honest question, not tr0lling- I wonder how it compares to the weight of Lithium batteries? Current batteries are a deal breaker for air travel. The range limit is about 200km before they get too heavy. Lithium batteries are really damned heavy. Just look at the curb weight of a small electric car. I’ve heard some speculation that H2 may be the only way to decarbonize air travel. All tne problems you describe are real and serious, but we may have no choice but to solve them.
That said, synthetic Jet A may be in the table as posted upthread, and there are new solid-state lithium batteries on the horizon which have double the energy density (or the same energy for half the weight) and that could get us over the line there.
Regardless, aviation will be the last thing to decarbonize, I suspect. It’s a tough one to fix.
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I’m a major supporter of progressive aviation carbon tax. 10% for your first round trip, 20% your second, 30% your third etc. maybe move up in increments of 20. It is the few who do the vast majority of travelling. Private jet fuel can start at 1000% as far as I’m concerned.
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I do like the idea of scrapping any flights that could be replaced with a train trip of similar duration. That would stoke investment in passenger rail and have a quick impact on carbon reduction vs. creating a new wonderfuel.
France is rolling out a rule like that. Seems to be a trial though
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And France already has a decent rail system. I remember a meal I ate in a train station in France about 15 years ago. It was absolutely fantastic and great value. Trains were excellent too!
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Yah this seems like a good idea.
If air travel was correctly priced (ie. including the cost of the negative externalities of pollution and climate change on society), trains would suddenly look a whole lot better to most people. Watch how fast people demand high speed rail when plane tickets triple in cost.
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But… but… Veronica! The market knows ALL! Are you implying that the market is somehow imperfect! /s
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Krugman’s followup
(no paywall on this link)
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I haven’t done the math to compare them, but my gut feel is that H2 and lithium batteries are both impractical for flight distances longer than a couple hour’s drive. Since flights shorter than a couple hour’s drive can mostly be replaced with ground-based transportation, there isn’t yet a practical case for broadly decarbonizing aviation.
Off the top of my head, I can think of a few flights where it makes sense to pursue decarbonization - Harbour Air’s Vancouver to Victoria flight springs to mind, along with hops between ridge-tops in Papua New Guinea. These are flights that are in demand for small aircraft and last about a half-hour.
The only thing I can see working to broadly reduce the CO2 impact of aviation are
- decent alternative transport (comfortable rail, ferry, etc)
- synfuels (which have an enormous energy cost)
- aggressive carbon taxing
- strong reforestation / afforestation / carbon sequestering programs
Regarding alternatives …
When my wife and I were in Germany, we took a quick holiday in Switzerland. The travel options were
- flying with a connection, because we were going between small cities - 4h door-to-door, or
- train, 8h door-to-door.
Didn’t hesitate - we took the train and had an awesome day picnicking on the train and watching the scenery roll by. Beautiful.
And I’m intrigued by airships as an air transport method where roads are poor or non-existent (e.g. mining, humanitarian relief, etc), but have no idea about the practicalities.
I’m hoping I’ve missed something, of course.
I suspect the same.
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The Eviation Alice claims a range of 250 nautical miles, which is over 460 km.
That might get revised downward a bit by the time it’s finished with testing and certification but it seems enough to be useful for certain connecting flights, even if it’s not going to replace long-haul flights any time soon.
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