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Comment by phkahler | Hacker News Reader

I always question if fuel cell / electric is really better than just burning the hydrogen in an engine.

We worked on an electric compressor motor for a fuel cell vehicle project once and it took more than one kilowatt (maybe 2 or 3 I don't recall) to run the compressor. An EV can do highway driving at a few KW so that seemed really inefficient. Aircraft run at higher continuous power so maybe it makes more sense, but I still wonder.

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Yeah the compressor load goes up with power - we have a 27 kW compressor for our 120kW PEM fuel cell here in the lab (this isn't what is going on the aircraft). This is one of the issues we are tackling with our unique system architecture for the aircraft.

How is the noise difference between electric and combustion engine?

One thing we have learned on this journey is how much low noise is to our customers and the wider community - we have yet to really put this under test and try and get a cost number against it i.e. how much more would you pay for a quieter engine? What we do have is an opportunity to be much quieter, but there is always a penalty to pay in terms of size. For example, unlike a battery aircraft, we still have to provide the fuel cells with air and we can do that with large quiet ducts or small noisy ones - but larger ones take up valuable real estate and ultimately add weight to the system. What I can say is we will design it to be quieter than current jet engines, but where we draw the line is tbd.

Fwiw, I love flying the B787 for many reasons, one of them being the low noise level. But… I wouldn’t go so far as to pay more money for it. The noise factor is not a decision driver, where seat size/leg room and service definitely are when it comes to choosing an airline/route.

The noise level is definitively a very important factor for the airplane operator.

A small low-noise plane can do some much more profitable routes than a high-noise one.

I've never flown on a 787 sadly but I have to say that the Embraer E195-E2 was also surprisingly comfy. Much more comfy than a 737, and thus far small jets had been terrible in my experience. Noisy, especially the back of the 717 beside the engines, cramped. But the Embraer was spacious and modern <3

IIRC for powered paragliders, it turned out propeller noise drowns out ICE noise.

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