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Am not well versed on these considerations but it appears one advantage of hydrogen is energy density compared to batteries. This may be less an issue for passe

Am not well versed on these considerations but it appears one advantage of hydrogen is energy density compared to batteries. This may be less an issue for passenger vehicles but could be more relevant for air travel - as an example. No comments or opinions otherwise re: funding etc. Found the below article useful as a primer: https://www.energy.gov/eere/fuelcells/articles/fuel-cell-and-battery-electric-vehicles-compared https://www.energy.gov/eere/fuelcells/articles/fuel-cell-and...

linsomniac 3y ago
Haven't we tried hydrogen for air travel before? ;-)
- Reason077 3y ago
  It's been used successfully for space travel, in liquid (cryogenic) form. The Space Shuttle's main engines ran on hydrogen fuel, for example. However the latest generation of rockets seems to have moved away from hydrogen back to things like RP-1 (kerosene) and liquid methane. The high cost and difficulties of working with hydrogen is a factor in this.
  - the-dude 3y ago
    Hindenburg
freedude 3y ago
They definitely fly better than a lead balloon (batteries).
jimt1234 3y ago
Engineering Explained occasionally discusses hydrogen energy density: https://www.youtube.com/watch?v=vJjKwSF9gT8 https://www.youtube.com/watch?v=vJjKwSF9gT8
spott 3y ago
What kind of energy density? There is energy density by volume (where it matches batteries, when you ignore all the stuff you need to keep hydrogen at 700bar safe), and energy density by weight (where it wins pretty handily against pretty much everything).
- dieselgate 3y ago
  Am not historically familiar with this topic though the attached paper above shows a comparative figure of Specific Energy in terms of Wh/Kg at both 5k and 10k psi Edit: interesting to do the conversion and realize 700bar is just over 10k psi - misunderstood the parent comment regarding "700bar safe" Edit2: further interesting to note how the 5k compression of the hydrogen has _higher_ Specific Energy density than 10k due to _decreased_ pressure vessel requirements
  - Retric 3y ago
    Just be careful with Hydrogen energy density as there’s a huge range of non obvious issues. Compressed you lose a great deal of energy converting it to kinetic energy and weight due to the containers + engines. Fuel cells also need electric motors and ideally a hybrid battery. Cryogenic fuel looks great until you need to have it sit around unused. Embrittlement, volume, cost, and a rage of safety hazards make it unappealing for aircraft or ships. So, my guess is the ideal long term solution barring “super batteries” is some sort of synthetic hydrocarbons that uses atmospheric CO2 but we are a long way from viability there.
DriverDaily 3y ago
Anybody who needs to run 24/7 and/or can't count on an electric grid could use hydrogen power: A logistics network, an army, public transportation, utility companies, forestry or mining...
- lazide 3y ago
  Or they could just use the well known https://en.m.wikipedia.org/wiki/Fischer–Tropsch_process https://en.m.wikipedia.org/wiki/Fischer–Tropsch_process to convert it the rest of the way to a hydrocarbon, not have the pesky raw hydrogen issues, and be able to use all their existing infrastructure to burn it? With the advantage of pulling carbon from the air in the process?
- dieselgate 3y ago
  This is a technical requirement often overlooked by the Consumer Market compared to the Commercial Market - the heavy and long usage of equipment in remote places (generators that run for days or shipping across oceans). Hydrogen may be a solution along with other hybrid approaches (WA state ferry electrification being relevant [1]) [1] https://wsdot.wa.gov/construction-planning/major-projects/ferry-system-electrification https://wsdot.wa.gov/construction-planning/major-projects/fe...
- Reason077 3y ago
  Not really, because if you don't have access to electricity then you very likely don't have access to hydrogen either. Hydrogen is much more difficult to transport and store compared to natural gas, gasoline, diesel, etc.
  - DriverDaily 3y ago
    Getting electricity out of hydrogen works the same way as getting electricity out of all the sources you mentioned, except your generator now produces zero emissions.
- cjrp 3y ago
  JCB are heavily in to hydrogen. They’ve shown how they can convert existing diesel equipment, and setup fuel bowsers on work sites.
deleted 3y ago
[deleted]
Pxtl 3y ago
Once you're already committed to green hydrogen (electrolysis-made hydrogen) you may as well go whole hog and do green methane (methane made through the Sabatier process, which consumes Hydrogen and CO2). Making a methane-powered jetliner is far more practical than a hydrogen-powered one.
- bryanlarsen 3y ago
  That's right, but there's an even better option: making synthetic kerosene from green H2 and CO2 so it can be used in existing jetliners.
ge96 3y ago
I thought it was hard to contain since the particle is so small (leaks). Liquid I suppose, temperature concern though.
scythe 3y ago
For boats, fuel cells can make sense. But air travel not only requires a high energy density but also a high power density, and here the fuel cells are relatively weak even by car standards. The alternative is to burn hydrogen, which introduces an inefficiency that eats up most of your advantage. For a car, you can have a small auxiliary battery, but a jet engine will run at max power for several minutes continuously during take-off, and for existing jet engines the power-to-weight ratio is considered a crucial figure of merit. For hydrogen storage, the DoE targets are truly sobering [1]. That whittles down hydrogen from roughly 100 times as dense as batteries to about 5. Throw a 50% thermodynamic efficiency (jet engines are not efficient!) on top of that and hydrogen still has an advantage, but it lags quite badly behind jet fuel. There have been four decades of intensive government-sponsored research effort into hydrogen storage materials, but all existing systems in practical use rely on fiber-composite tanks at 700 bar. You get better results with an ammonia-burning jet engine. Here the tank weight is negligible and the hydrogen storage density is effectively 15% (after correcting for the enthalpy of formation). But ammonia still has just half the energy density of jet fuel, and it's rather unpleasant to work with. Plus, the existing production process of ammonia faces its own serious inefficiencies, and extensive investigation of more efficient ammonia production has been painstaking with only one Japanese startup [3] that is behind its timeline (probably a little COVID-influenced) and other contenders at lab stage. With the direct ammonia fuel cell, the power density issue is even worse, but the energy density is very good. This technology competes well with fossil fuels for weight-sensitive applications that do not require high power (DARPA has been interested in a DAFC drone). But ammonia fuel cells are mostly at lab stage, partially because ammonia production remains disappointing (despite a theoretical energy cost of zero) despite considerable research effort. 1: https://www.energy.gov/eere/fuelcells/hydrogen-storage https://www.energy.gov/eere/fuelcells/hydrogen-storage 2: https://www.google.com/search?client=firefox-b-1-lm&q=tsubame+bhb https://www.google.com/search?client=firefox-b-1-lm&q=tsubam...

linsomniac 3y ago

Haven't we tried hydrogen for air travel before? ;-)

Reason077 3y ago
It's been used successfully for space travel, in liquid (cryogenic) form. The Space Shuttle's main engines ran on hydrogen fuel, for example. However the latest generation of rockets seems to have moved away from hydrogen back to things like RP-1 (kerosene) and liquid methane. The high cost and difficulties of working with hydrogen is a factor in this.
- the-dude 3y ago
  Hindenburg

freedude 3y ago

They definitely fly better than a lead balloon (batteries).

jimt1234 3y ago

Engineering Explained occasionally discusses hydrogen energy density: https://www.youtube.com/watch?v=vJjKwSF9gT8 https://www.youtube.com/watch?v=vJjKwSF9gT8

spott 3y ago

What kind of energy density? There is energy density by volume (where it matches batteries, when you ignore all the stuff you need to keep hydrogen at 700bar safe), and energy density by weight (where it wins pretty handily against pretty much everything).

dieselgate 3y ago
Am not historically familiar with this topic though the attached paper above shows a comparative figure of Specific Energy in terms of Wh/Kg at both 5k and 10k psi Edit: interesting to do the conversion and realize 700bar is just over 10k psi - misunderstood the parent comment regarding "700bar safe" Edit2: further interesting to note how the 5k compression of the hydrogen has _higher_ Specific Energy density than 10k due to _decreased_ pressure vessel requirements
- Retric 3y ago
  Just be careful with Hydrogen energy density as there’s a huge range of non obvious issues. Compressed you lose a great deal of energy converting it to kinetic energy and weight due to the containers + engines. Fuel cells also need electric motors and ideally a hybrid battery. Cryogenic fuel looks great until you need to have it sit around unused. Embrittlement, volume, cost, and a rage of safety hazards make it unappealing for aircraft or ships. So, my guess is the ideal long term solution barring “super batteries” is some sort of synthetic hydrocarbons that uses atmospheric CO2 but we are a long way from viability there.

DriverDaily 3y ago

Anybody who needs to run 24/7 and/or can't count on an electric grid could use hydrogen power: A logistics network, an army, public transportation, utility companies, forestry or mining...

lazide 3y ago
Or they could just use the well known https://en.m.wikipedia.org/wiki/Fischer–Tropsch_process https://en.m.wikipedia.org/wiki/Fischer–Tropsch_process to convert it the rest of the way to a hydrocarbon, not have the pesky raw hydrogen issues, and be able to use all their existing infrastructure to burn it? With the advantage of pulling carbon from the air in the process?
dieselgate 3y ago
This is a technical requirement often overlooked by the Consumer Market compared to the Commercial Market - the heavy and long usage of equipment in remote places (generators that run for days or shipping across oceans). Hydrogen may be a solution along with other hybrid approaches (WA state ferry electrification being relevant [1]) [1] https://wsdot.wa.gov/construction-planning/major-projects/ferry-system-electrification https://wsdot.wa.gov/construction-planning/major-projects/fe...
Reason077 3y ago
Not really, because if you don't have access to electricity then you very likely don't have access to hydrogen either. Hydrogen is much more difficult to transport and store compared to natural gas, gasoline, diesel, etc.
- DriverDaily 3y ago
  Getting electricity out of hydrogen works the same way as getting electricity out of all the sources you mentioned, except your generator now produces zero emissions.
cjrp 3y ago
JCB are heavily in to hydrogen. They’ve shown how they can convert existing diesel equipment, and setup fuel bowsers on work sites.

deleted 3y ago

[deleted]

Pxtl 3y ago

Once you're already committed to green hydrogen (electrolysis-made hydrogen) you may as well go whole hog and do green methane (methane made through the Sabatier process, which consumes Hydrogen and CO2). Making a methane-powered jetliner is far more practical than a hydrogen-powered one.

bryanlarsen 3y ago
That's right, but there's an even better option: making synthetic kerosene from green H2 and CO2 so it can be used in existing jetliners.

ge96 3y ago

I thought it was hard to contain since the particle is so small (leaks). Liquid I suppose, temperature concern though.

scythe 3y ago

For boats, fuel cells can make sense. But air travel not only requires a high energy density but also a high power density, and here the fuel cells are relatively weak even by car standards. The alternative is to burn hydrogen, which introduces an inefficiency that eats up most of your advantage. For a car, you can have a small auxiliary battery, but a jet engine will run at max power for several minutes continuously during take-off, and for existing jet engines the power-to-weight ratio is considered a crucial figure of merit. For hydrogen storage, the DoE targets are truly sobering [1]. That whittles down hydrogen from roughly 100 times as dense as batteries to about 5. Throw a 50% thermodynamic efficiency (jet engines are not efficient!) on top of that and hydrogen still has an advantage, but it lags quite badly behind jet fuel. There have been four decades of intensive government-sponsored research effort into hydrogen storage materials, but all existing systems in practical use rely on fiber-composite tanks at 700 bar. You get better results with an ammonia-burning jet engine. Here the tank weight is negligible and the hydrogen storage density is effectively 15% (after correcting for the enthalpy of formation). But ammonia still has just half the energy density of jet fuel, and it's rather unpleasant to work with. Plus, the existing production process of ammonia faces its own serious inefficiencies, and extensive investigation of more efficient ammonia production has been painstaking with only one Japanese startup [3] that is behind its timeline (probably a little COVID-influenced) and other contenders at lab stage. With the direct ammonia fuel cell, the power density issue is even worse, but the energy density is very good. This technology competes well with fossil fuels for weight-sensitive applications that do not require high power (DARPA has been interested in a DAFC drone). But ammonia fuel cells are mostly at lab stage, partially because ammonia production remains disappointing (despite a theoretical energy cost of zero) despite considerable research effort. 1: https://www.energy.gov/eere/fuelcells/hydrogen-storage https://www.energy.gov/eere/fuelcells/hydrogen-storage 2: https://www.google.com/search?client=firefox-b-1-lm&q=tsubame+bhb https://www.google.com/search?client=firefox-b-1-lm&q=tsubam...