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hiles_adam t1_jaqdn93 wrote

Reply to comment by MightyH20 in Universal Hydrogen Successfully Completes First Flight of Hydrogen Regional Airliner by tooch_my_gooch

>and two large hydrogen tanks with 30 kg of fuel. Beneath the plane’s right wing, an electric motor from magniX was being driven by the new hydrogen fuel cell from Plug Power.
>
>Today’s 15-minute flight used about 16kg of gaseous hydrogen — half the amount stored in two motorbike-sized tanks within the passenger compartment. Universal Hydrogen plans to convert its test aircraft to run on liquid hydrogen later this year.

Found this in another article because I was curious as well

for 15 minutes of flight a 747 burns 3600L of aviation fuel, or 2880kg o.o that sounds so wrong but thats what google is telling me

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MightyH20 t1_jaqk2c6 wrote

Thanks for looking it up! Usefull information that this article has left out imo.

>Today’s 15-minute flight used about 16kg of gaseous hydrogen — half the amount stored in two motorbike-sized tanks within the passenger compartment.

That is interesting. 1 kilograms of hydrogen equals to 33.33 kWh of useable energy. This means the entire flight consumed only 533.28 kWh.

I wonder under what pressure the hydrogen was stored given the relatively small size of the tanks with the total capacity to hold 30 kilograms.

>for 15 minutes of flight a 747 burns 3600L of aviation fuel, or 2880kg

This could be correct though. I know that a 747 uses around 3 to 4 liters of kerosine every second! And shows the massive efficiency difference between both technologies. 3600 L of kerosine equals to 37,564 kWh.

However, the major difference is probably the weight of the planes and that a 747 uses jet engines whereas this was a smaller prop-plane.

Perhaps a better comparison would be a comparison to a standard propellor plane. According to "the internet" a standard propellor plane uses 900 gallons of kerosine an hour or 225 gallons per 15 minutes. That equals to 8888 kWh.

Conclusion

Hydrogen prop plane 15 minutes flight: 533 kWh energy (16kg of hydrogen) consumption.

Standard fossil prop plane 15 minutes flight: 8888 kWh energy (225 gallons of kerosine) consumption

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tantricengineer t1_jarnif0 wrote

These systems must store hydrogen at thousands of PSI for the energy density to rival petrol based fuels. The ideal storage state is nearer to 10,000 PSI where hydrogen becomes slurpy-like in composition.

The material science is coming along. One challenge with hydrogen fuel tanks is if a tank is punctured in an accident, you have rapid expansion of hydrogen gas as it equalizes to atmospheric pressure, and a likely fire which has little color. (Look at the FLIR view here: https://youtu.be/0aDC2ZmikRE )

This makes it difficult to determine where flames are.

Still rooting for this tech though since it gives us amazing possibilities.

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kyckling666 t1_jarrzfd wrote

Guys I grew up with in oil and gas used straw brooms for invisible fire detection.

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jawshoeaw t1_jasas4x wrote

in an aircraft I'm guessing explosive decompression is the bigger problem, seeing as visualizing a fire on your wing really isn't changing your plan in the short term lol

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tantricengineer t1_jat4mfi wrote

I don't expect these tanks to blow up in flight. I expect them to blow up when most commercial aircraft accidents happen: on the ground / takeoff / landing.

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jawshoeaw t1_jat9lnt wrote

Ohhh gotcha. But sadly that’s rarely survivable with current fuels. I could see some edge case where there’s a survivable landing but here’s the actual advantage of hydrogen, the high pressure vessels are necessarily quite strong and might do better in a crash even if the broke open compared to avgas

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InsuranceToTheRescue t1_jasszm4 wrote

I believe since the tanks are pressurized that they would likely explosively ignite instead of making a sustained flame. Then these vehicles really could blow up like in the movies.

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razorirr t1_jarg2c5 wrote

Its quite a bit more than that. It takes 55kwh to crack the water to get that h2 using hydrolosis

A question becomes then if planes are 10% of us transit emissions, all other large transit 10%, and our personal cars are 45% and semis are 35%. Should we be using energy to do this? That same solar would most likely reduce emissions more if you put it directly into cars / busses / semis as battery electric. You dont have the conversion loss, and BEV is 10-15% more efficent than FCEV

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jschubart t1_jas8dvl wrote

You sure your numbers for prop planes are for 15 minutes and not an hour? This looks similar to the size of a Saab 340 which burns about 119 gallons/hr.

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empireofjade t1_jaut5t4 wrote

During the test flight of this aircraft only one prop was hydrogen powered. The aircraft was also powered by a conventional turboprop for safety reasons, so your numbers are not right.

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MightyH20 t1_jav2d1b wrote

Aah that makes sense. In that case it would be too complex to calculate it.

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Gloriathewitch t1_jaqo3sg wrote

This is probably an average, they'd use most of that on acceleration I'd wager, but coasting in the sky takes very little thrust.

Also, fun fact from a mechanic: accelerating briskly to 60mph can increase your mpg as opposed to slowly ramping up your speed, as the burst consumes more however the sooner you coast the sooner you start conserving fuel.

Draft behind semis if you want even better mpg, your car not having to overcome the wind makes the car have to barely work.

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asdaaaaaaaa t1_jaqp3ap wrote

>Draft behind semis if you want even better mpg, your car not having to overcome the wind makes the car have to barely work.

They also tend to drive more reliably towards saving fuel than zipping around, changing speed or lanes all the time, and doing other things that would waste more fuel.

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InsuranceToTheRescue t1_jasrbz7 wrote

Yeah, but semis always seem to destroy my windshield with rocks, and not being able to see over or around them makes me uncomfortable.

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irrelevantmango t1_jaraqdo wrote

Don't get too close behind them, semi drivers can get cranky if they know you are there but they cannot see you in their mirrors.

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Gloriathewitch t1_jaslmea wrote

You're good to draft a fair distance as the air is already disturbed.

Its what makes giant brick shaped trucks so great, they disturb the air so much that you can save gas.

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_toodamnparanoid_ t1_jask17f wrote

I found that for turbine aircraft you want to get to altitude faster for the same reason. A max thrust climb will burn at a higher rate but you get to altitude so much faster and the burn rate four every thousand feet you climb drops significantly. That's not just to enter cruise but also the efficiency at altitude.

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jawshoeaw t1_jasajd4 wrote

would clarify that while slowly ramping can be inefficient, flooring the accelerator, depending on the vehicle can also be inefficient .The principle being an engine under load is more efficient , but only up to a point again depending on design. but in this case, the motor was electric so no reason not to goose it :)

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elatedwalrus t1_jaqy6vn wrote

You should also consider the voluke of each fuel. An airliner fits that much fuel mostly in its wings

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Icy_Comparison148 t1_jayjfxw wrote

Yeah that sounds about right. That’s a big as jet though, I think it’s 3600 gallons per hour. A 757 burns about a third of that per hour in cruise. A dash 8 burns about maybe 175 to 200 gallons per hour. Which looks like what this plane is based on.

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