4 ms·

80% is propulsive efficiency from the shaft to useful thrust, there's a lot more energy lost between the fuel input and shaft output (thermodynamic efficiency).

80% is propulsive efficiency from the shaft to useful thrust, there's a lot more energy lost between the fuel input and shaft output (thermodynamic efficiency). The thermodynamic efficiency is where most energy is wasted. For small turboprop engines, this is only 25-30%. There are a lot of advantages to a fuel cell commuter plane: -lower exterior noise: important for accessing smaller, less congested airports -lower interior noise: noise is a big reason airlines use regional jets instead of more efficient turboprops -potentially lower operating costs: a small turboprop might cost $300/hour in fuel and $150/hour in engine maintenance. A fuel cell could potentially be lower cost overall. -redundancy: can still generate thrust on battery or fuel cell power

danans 7y ago
> 80% is propulsive efficiency from the shaft to useful thrust, there's a lot more energy lost between the fuel input and shaft output (thermodynamic efficiency). The thermodynamic efficiency is where most energy is wasted. For small turboprop engines, this is only 25-30%. Ah, I see, so "propellant" in propulsive energy refers to the ignited fuel/air mixture, not accounting for thermal losses caused by fuel ignition. Given that, the efficiency case for H2 fuel-cell flight is even better than I expected (and it was already pretty good). I'm guessing they also don't lose efficiency to noise and vibration.