Hydrogen specific energy is 141 MJ/kg. While jet fuel is 42 MJ/kg, or about 3x greater for hydrogen.

I think you may have your units confused though, Jet Fuel is about 11,900 WH/kg, but Hydrogen is 39,000 WH/kg, again, a little over 3x greater for hydrogen. (again hydrogen has the highest specific energy by mass)

I suspect you mean to compare volume or energy density per volume (liter or gallons), where fossil fuels have about 10x the energy per volume. That means hydrogen takes up much more space.

But no fuel has more energy per mass than hydrogen.

Even decade-old research papers indicate commercially available hydrogen storage at 1400w/kg using composite storage tanks.

I'm not arguing against fossil fuel powered airplanes.

But I would estimate a fuel-cell powered electric airplane approaches an actually useful design, versus one based on rechargeable batteries, in range and payload capacity, not to mention the rapidity of refueling.

The energy density depends on whether you count the tanks. For avgas or jet fuel, the tank weight is small compared to the fuel weight. For hydrogen, the tank weight can be much larger than the fuel weight - except for large cryogenic tanks.







Hydrogen specific energy is 141 MJ/kg. While jet fuel is 42 MJ/kg, or about 3x greater for hydrogen.

I think you may have your units confused though, Jet Fuel is about 11,900 WH/kg, but Hydrogen is 39,000 WH/kg, again, a little over 3x greater for hydrogen. (again hydrogen has the highest specific energy by mass)

I suspect you mean to compare volume or energy density per volume (liter or gallons), where fossil fuels have about 10x the energy per volume. That means hydrogen takes up much more space.

But no fuel has more energy per mass than hydrogen.

Even decade-old research papers indicate commercially available hydrogen storage at 1400w/kg using composite storage tanks.

I'm not arguing against fossil fuel powered airplanes.

But I would estimate a fuel-cell powered electric airplane approaches an actually useful design, versus one based on rechargeable batteries, in range and payload capacity, not to mention the rapidity of refueling.

I did count the tanks...

Hydrogen is way, way better than lithium-ion batteries, which are not only heavy, they also have to enclosed in a large, heavy, metal case...

The fuel cell is not very heavy. About the same as a Rotax.

It would be quite reasonable to build and fly a hydrogen fuel cell light-sport and get a couple of hours or more range out of it.

I'm seeing hydrogen (no tanks) as about 2.5X the energy density (when burned) as Kerosene:

https://www.energy.gov/eere/fuelcells/hydrogen-storage

If your above, 60KG of tanks for 6KG of hydrogen is correct, then hydrogen including tanks has about 1/4 the energy density of kerosene including tanks (which are minimal for kerosene). That is your above 700 bar (10,000 psi).

That isn't crazy, but if I look at my baron, I carry 140 gallons of fuel (840 pounds) out of 5100# or airplane. If I increase than 840 to 3200, I have no useful load left.

Clearly a hydrogen powered plane needs to be designed differently.

For large aircraft, cryogenic storage is fine - the tanks do not need to store very long (the airplanes have high use factor) and the complexity of the tanks is not such a big deal relative to the aircraft size.

Of course large aircraft have a higher percentage of fuel vs total weight, so they will need the higher density storage.

Maybe there is a way to make light planes use H2, but they are such a small user of fossil fuels, it doesn't seem worth the engineering investment.

I think a reasoable approach to climate change is to go after the ~80% easiest targets and live with 20% of the current emissions. That last 20% can get very expensive