91–100 of 343 posts
Small-scale alcohol fuel production integrated into regenerative agriculture farms is different from mass ethanol production.
You can ferment anything that has starch or sugar, the leftovers from the distillation can be composted or fed to livestock. Most existing internal combustion engines can be modified to use alcohol fuel. And it's carbon-neutral.
Hydrogen has an efficiency problem. You need to convert other forms of energy to hydrogen at a loss. Then you need to store it and transport it, which is costly and may impose quite some energy cost for cooling or compression. Then you need to convert it back to electricity, also at a loss. If you start at electricity, the electrical grid and batteries would be much more efficient. If you start at oil or gas, you cou…
There are other ways of generating electricity apart from electrolysis. For example, from food waste through yeast and other methods. Yes, there is some energy being used but you are talking about material which would go waste anyway: https://fuelcellsworks.com/news/a-simplified-way-to-turn-foo... First: Energy density The primary advantage of hydrogen is energy density. Though Li Ion and other technologies have impr…
How is it better than generating biogas from biomaterial, something we already do at industrial scale? What’s the advantage of biohydrogen over biomethane?
Earlier quoted context omitted.
The issue of charging was also there with BEVs, until Tesla straight up built a huge network of superchargers. The players in hydrogen say they will do the same. But for personal vehicles, hydrogen won't math out, it's greatest advantage is its energy density for trucks. It's for long range trucks that we will see hydrogen first. Green hydrogen will act as energy storage, big renewables grids can dump excess into gre…
Maybe ships is an even better fit than trucks?
As planes and boats expend fuel, they get lighter, so less fuel is needed to move the second half of the journey, and less for the last quarter, etc. That “bonus” doesn’t work out with batteries, you need to move all the weight for all the journey. The energy density of batteries, to my understanding, just doesn’t add up correctly for boats or most airplanes.
What I would like to know is, wouldn’t a hydrogen-powered boat or plane not only have a similar calculation on how much fuel is needed, but also (in the case of boats) be even cheaper to move because its fuel payload is lighter than water? Water 997kg/m3 vs liquid hydro 71kg/m3, also gasoline 783kg/m3, sounds like a nice bonus for jumbo jets too. (I am NOT a physicist or mechanical engineer)
Gasoline-powered sea vessels are terrible polluters, incidentally, accounting for 18% of all air pollution. Between the air pollution benefits and possibility of the vessels being so much more fuel efficient, it seems like hydrogen would be a benefit even if the production isn’t completely clean.
Earlier quoted context omitted.
There are other ways of generating electricity apart from electrolysis. For example, from food waste through yeast and other methods. Yes, there is some energy being used but you are talking about material which would go waste anyway: https://fuelcellsworks.com/news/a-simplified-way-to-turn-foo... First: Energy density The primary advantage of hydrogen is energy density. Though Li Ion and other technologies have impr…
> For example, from food waste through yeast and other methods. How is it better than generating biogas from biomaterial, something we already do at industrial scale? What’s the advantage of biohydrogen over biomethane?
Earlier quoted context omitted.
Transporting hydrogen is expensive. It also has a tendency to leak.
> It also has a tendency to leak. But I mean, that has to be a limitation of current technology, right? There has to be engineering solutions that we can devise to make it as safe statistically as for example gasoline transport?
And the leaked gas, especially if in an enclosed space, is flammable or explosive over a very wide range of concentrations.
Long-term storage, transport, and use, at scale, is hugely problematic.
https://www.sciencedirect.com/topics/engineering/hydrogen-mo...
https://en.wikipedia.org/wiki/Hydrogen_embrittlement
https://www.sciencedirect.com/topics/engineering/hydrogen-ex...
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Electricity has a transmission problem though - there are some parts of the world with lots of clean energy, which we can't fully take advantage of because we can't transport electricity that far. Hydrogen allows us to use that clean energy to power cars in other parts of the world, since you can produce hydrogen in those places and then ship it to places without much clean energy. Also you can presumably stop and st…
Do you know more about hydrogen transport? I heard it is quite more complicated and expensive than LNG (closest equivalent), because hydrogen leaks more easily.
Earlier quoted context omitted.
Maybe ships is an even better fit than trucks?
I was wondering the same thing, from a density perspective. And similarly for airplanes. As planes and boats expend fuel, they get lighter, so less fuel is needed to move the second half of the journey, and less for the last quarter, etc. That “bonus” doesn’t work out with batteries, you need to move all the weight for all the journey. The energy density of batteries, to my understanding, just doesn’t add up correctl…
For metal-air batteries, one of the more promising areas of research, the problem is actually worse: the cells gain mass as oxygen is reacted with the metal anode, discharging the battery.
https://en.wikipedia.org/wiki/Metal–air_electrochemical_cell
For marine propulsion, heavy fuels are typically preferred (bunker fuel typically, thogh deisel and petrol engines do exist). Much of the pollution is in the form of particulates and sulfer emissions. You can actually see major shipping routes on atmospheric sensing maps by SO2 emissions:
https://earth.nullschool.net/#current/chem/surface/level/ove...
As long-term risks these are ... somewhat minor as these contaminants settle out quickly: in days to months rather than centuries to millennia for CO2 and methane. Not great for respiratory health, but not the long-term planetary risk fossil fuel combustion overall is.
Hydrogen has an efficiency problem. You need to convert other forms of energy to hydrogen at a loss. Then you need to store it and transport it, which is costly and may impose quite some energy cost for cooling or compression. Then you need to convert it back to electricity, also at a loss. If you start at electricity, the electrical grid and batteries would be much more efficient. If you start at oil or gas, you cou…
All production issues aside, aviation makes sense to me. Planes are only filling at known stops, the weight is superior to our best batteries, and the transition from fossil fuel to hydrogen jets should be easy.
As for as long haul trucks, I can kinda see it, maybe, still a lot of storage, production, efficiency issues. Weight isn’t nearly the same concern as it is for aviation.
For cars, yea, I don’t see it.
Hydrogen has an efficiency problem. You need to convert other forms of energy to hydrogen at a loss. Then you need to store it and transport it, which is costly and may impose quite some energy cost for cooling or compression. Then you need to convert it back to electricity, also at a loss. If you start at electricity, the electrical grid and batteries would be much more efficient. If you start at oil or gas, you cou…
There are other ways of generating electricity apart from electrolysis. For example, from food waste through yeast and other methods. Yes, there is some energy being used but you are talking about material which would go waste anyway: https://fuelcellsworks.com/news/a-simplified-way-to-turn-foo... First: Energy density The primary advantage of hydrogen is energy density. Though Li Ion and other technologies have impr…
Simply, it is by far the best of all possible aircraft fuels.
Its one major disadvantage for this, as for most uses, is its low mass density: it needs more room than diesel to store enough to be useful. The tanks need to be bigger, and either strong enough to contain high pressure, or well-enough insulated to keep it liquid.
Current aircraft store fuel in wing tanks not roomy enough for hydrogen. The most practical hydrogen-fueled aircraft would probably have a shape more like a lifting body than a submarine with skinny wings sticking out. So for best efficiency, we might need new airframes, but just using hydrogen yields major improvement. To oversimplify, the plane doesn't need to lift so much weight of fuel to cruising altitude, or carry it halfway across the world.
Tankage has improved radically in recent years with the development of aerogels, which make practical carrying liquid hydrogen that need not held be at high pressure, so can be in tanks that conform to an aerodynamically-practical shape. (Other sophisticated storage methods increase weight, so are more practical on the ground.)
Hydrogen is tricky to store for long or in large amounts, so the best way to use it is to produce it on demand where it is needed. A major airport would be a good place to produce it, as it could be piped directly into aircraft and used immediately. All the airport would need is water and power. Power can be collected by wind and solar over a wide area, delivered by transmission lines. The amount of water needed is negligible.
Producing hydrogen would also yield plenty of oxygen, which might just be vented; but by carrying liquid oxygen, aircraft could fly higher, faster, and more efficiently, or at least get to cruising altitude more quickly. As electric power continues to get cheaper, uses for it such as liquifying oxygen along with hydrogen get more attractive.
The first use will be in long-haul craft operating from a few major airports. It is possible that current large aircraft -- 747s, 777s, A380s -- could be converted, by using some of what is now cargo space for tankage, and replacing fuel pipes and pumps and, quite possibly, engines. It would be a big job, made attractive mainly by the extreme cost of qualifying new airframe designs.
The lost cargo space would be made up easily by the much larger weight capacity, as tens of tons less weight of fuel is needed. Cargo aircraft today often fly half-empty so as not to exceed their takeoff weight limit.
Hydrogen is sexy but alcohol matches our existing context better. Small-scale alcohol fuel production integrated into regenerative agriculture farms is different from mass ethanol production. You can ferment anything that has starch or sugar, the leftovers from the distillation can be composted or fed to livestock. Most existing internal combustion engines can be modified to use alcohol fuel. And it's carbon-neutral.
There are some marginal gains possible, but on the order of single-digit percentages of present fossil fuel consumption. Maybe low double-digits.
The US had a largely biofuel based transport system in 1900. Horses consumed 20% of all US grain production, the population was under 100m, and transport generally was a small fraction of today's values (or at least last year's) per capita: closer to 300 mi/yr, much of that walking, than 15,000.