5 ms·

Hydrogen is the way for aircraft / long-haul vehicles. It's not about conversion efficiency it's about energy density v weight.

martythemaniak 5y ago
Electric flight today is always about short-haul flight, ranging from air-taxi eVTOLs like Joby to more normal planes like Eviation's Alice, but all less than 1000km in range.
umvi 5y ago
Storing a lot of hydrogen at high pressure requires heavy tanks. Storing a lot of hydrogen at low pressure results in the Hindenburg.
- ncmncm 5y ago
  So, no one would ever use compressed hydrogen for transport aircraft. LH2 tanks weigh practically nothing.
  - dragonwriter 5y ago
    > LH2 tanks weigh practically nothing. Volume, though, is an issue and impacts aerodynamic design.
    - ncmncm 5y ago
      The weight advantage will prove decisive. On routes served by LH2-fueled transports, the kerosene-fueled dinosaurs will be wholly unable to compete.
  - adgjlsfhk1 5y ago
    you need to either compress or cryogenically cool. At 1atm and normal temp, hydrogen is about 8x less energy per volume then her fuel.
    - ncmncm 5y ago
      Volume is cheap, in aircraft. Weight is dear.
  - leaded_syrinx 5y ago
    We already have drones that can hover for hours using hydrogen in carbon fiber tanks... https://www.borntoengineer.com/hydrogen-powered-drone-sets-world-record https://www.borntoengineer.com/hydrogen-powered-drone-sets-w...
    - ncmncm 5y ago
      Tiny aircraft have an enormous advantage over those big enough to move much. It is easy to make an RC plane that can fly straight up. Or, an ornithopter. A 747 flying straight up is impossible. A 747-sized ornithopter is impossible. Those "tictacs" swooping around navy ships are most likely liquid-fueled drones. If they haven't shot any down yet, that is a disgrace.
dghughes 5y ago
Why does an electric airplane need to use batteries for storage? I'd say advance the technology by using other sources of power if possible. Instead of compressed liquid hydrogen which is hard to contain maybe some type of heated metal-hydride using hydrogen. Convert with a fuel cell, maybe batteries as a buffer and for their efficiency. Event that weird PowerPaste stuff may be suitable too. https://en.wikipedia.org/wiki/Powerpaste https://en.wikipedia.org/wiki/Powerpaste I've seen 30kWh to 50kWh per 100kg of hydrogen metal hydride. The linked says says Tesla is about 75kWh per 453kg (1,000 lbs) and the Joby S4 claims 150kWh 907kg (2,000 lbs). Batteries would be more efficient but if hydrogen metal-hydride is 50kWh/100kg a Tesla could have 340kWh at the same weight of storage or lose 300kg and still have 75kWh.

martythemaniak 5y ago

Electric flight today is always about short-haul flight, ranging from air-taxi eVTOLs like Joby to more normal planes like Eviation's Alice, but all less than 1000km in range.

umvi 5y ago

Storing a lot of hydrogen at high pressure requires heavy tanks. Storing a lot of hydrogen at low pressure results in the Hindenburg.

ncmncm 5y ago
So, no one would ever use compressed hydrogen for transport aircraft. LH2 tanks weigh practically nothing.
- dragonwriter 5y ago
  > LH2 tanks weigh practically nothing. Volume, though, is an issue and impacts aerodynamic design.
  - ncmncm 5y ago
    The weight advantage will prove decisive. On routes served by LH2-fueled transports, the kerosene-fueled dinosaurs will be wholly unable to compete.
- adgjlsfhk1 5y ago
  you need to either compress or cryogenically cool. At 1atm and normal temp, hydrogen is about 8x less energy per volume then her fuel.
  - ncmncm 5y ago
    Volume is cheap, in aircraft. Weight is dear.
- leaded_syrinx 5y ago
  We already have drones that can hover for hours using hydrogen in carbon fiber tanks... https://www.borntoengineer.com/hydrogen-powered-drone-sets-world-record https://www.borntoengineer.com/hydrogen-powered-drone-sets-w...
  - ncmncm 5y ago
    Tiny aircraft have an enormous advantage over those big enough to move much. It is easy to make an RC plane that can fly straight up. Or, an ornithopter. A 747 flying straight up is impossible. A 747-sized ornithopter is impossible. Those "tictacs" swooping around navy ships are most likely liquid-fueled drones. If they haven't shot any down yet, that is a disgrace.

dghughes 5y ago

Why does an electric airplane need to use batteries for storage? I'd say advance the technology by using other sources of power if possible. Instead of compressed liquid hydrogen which is hard to contain maybe some type of heated metal-hydride using hydrogen. Convert with a fuel cell, maybe batteries as a buffer and for their efficiency. Event that weird PowerPaste stuff may be suitable too. https://en.wikipedia.org/wiki/Powerpaste https://en.wikipedia.org/wiki/Powerpaste I've seen 30kWh to 50kWh per 100kg of hydrogen metal hydride. The linked says says Tesla is about 75kWh per 453kg (1,000 lbs) and the Joby S4 claims 150kWh 907kg (2,000 lbs). Batteries would be more efficient but if hydrogen metal-hydride is 50kWh/100kg a Tesla could have 340kWh at the same weight of storage or lose 300kg and still have 75kWh.