Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: Future of carbon-free aviation ?
metalresearcher
International Hazard
*****




Posts: 614
Registered: 7-9-2010
Member Is Offline

Mood: Reactive

[*] posted on 31-1-2021 at 08:24
Future of carbon-free aviation ?


Aviation is one of the biggest CO2 producers. Now many companies and institutions are researching on alternatives, now more than ever.

These alternatives are:
* Hydrogen. Energy to mass ratio is much better than Jet-A1 (current kerosene fuel), but energy to volume ratio is much worse. H2 tanks take lots of space, regardless whether compressed to 700 bar or liquefied (which requires additionally cryogenic tanks of -252 C).
* Batteries (i.e. electric planes). Tesla batteries (Li-ION) are 400Wh/kg, which is way too heavy. When it becomes e.g. 1000Wh /kg, then only short haul (< 1000km) flights are feasible, but forget about intercontinental flights up to 10000km.
* Ammonia. Nice article: https://newatlas.com/aircraft/reaction-engines-ammonia-carbo... but I think, it emits NOx as well and much more than current kerosene based aircraft. And liquid NH3 should be kept under -33 C, also when on the ground as well.
* CCS, Carbon Capture and Storage. This article advocates it https://www.sciencedaily.com/releases/2021/01/210113100810.h... as 'sustainable', but putting CO2 in the ground does indeed not heat up the atmosphere (assumed it is not leaking), but it is still creating waste and not a circular economy. Moreover, there is already wasteless CCS and that are devices called 'trees'. But we are logging all these green lungs of Earth in Brasil, Congo, Indonesia. So at least stop this first.
* CCU or Synfuel. This filters CO2 from the air as seen in these videos.
https://www.youtube.com/watch?v=_kVT77n67UY
https://www.youtube.com/watch?v=bvwnvYvMPyo
https://www.youtube.com/watch?v=s1-soaZn4B0
The CO2 will react with water with a CeO2 catalyst which created syngas (CO + H2). This will be processed with the Fischer-Tropsch process (which ia already used commercially for several decades to make oil from coal gas) and that results synthetic crude oil of which Jet-A1 (and other petroleum based products) can be made.
Currently, it is expensive and requires renewable energy (otherwise it is useless), but maybe in the 30s or 40s (before 2050) it might be feasible.
This requres no redesign of aircraft as it is almost the same fuel, with the difference it is not fossil.

What are your ideas ?
View user's profile View All Posts By User
DBX Labs
Hazard to Self
**




Posts: 52
Registered: 24-12-2020
Member Is Offline


[*] posted on 31-1-2021 at 08:47


I think that biofuels will be a big development in upcoming years. I’m not sure which route would be used to turn produced ethanol into lengthier hydrocarbons for use in jet engines, but like you said, plants are the best carbon capture we have (even if it only reduces CO2 to carbohydrates).



View user's profile View All Posts By User
Fulmen
International Hazard
*****




Posts: 1455
Registered: 24-9-2005
Member Is Offline

Mood: Bored

[*] posted on 31-1-2021 at 10:03


Quote: Originally posted by metalresearcher  
Aviation is one of the biggest CO2 producers.


No it's not. Heat and electricity is the biggest with 40%, road transport produces appr 15%. Aviation barely registers with some 2-3%.




We're not banging rocks together here. We know how to put a man back together.
View user's profile View All Posts By User
Fyndium
International Hazard
*****




Posts: 946
Registered: 12-7-2020
Location: Not in USA
Member Is Offline


[*] posted on 31-1-2021 at 11:26


Heating, transportation, concrete and metal industries prioritize in CO2 emissions. CO2 produced is high in aviation per unit, but overall it is a small percentage.

Combustible fuels can be made through synthetic or biosynthetic means and they can be directly utilized to existing, matured technology. Hydrogen was never an option, as it's density is mere 70kg/M3 and energy density per kg only a bit over 2x of LPG.

Possibly some simple compound that could be mass produced from syngas or some other single step scalable industrial process that is energy intensive, that is liquid at big temp range and possesses high energy density with very clean combustion would be an option in the future. Not sure what it would be, though.
View user's profile View All Posts By User
metalresearcher
International Hazard
*****




Posts: 614
Registered: 7-9-2010
Member Is Offline

Mood: Reactive

[*] posted on 31-1-2021 at 12:21


Quote: Originally posted by Fyndium  
Heating, transportation, concrete and metal industries prioritize in CO2 emissions. CO2 produced is high in aviation per unit, but overall it is a small percentage.

Combustible fuels can be made through synthetic or biosynthetic means and they can be directly utilized to existing, matured technology. Hydrogen was never an option, as it's density is mere 70kg/M3 and energy density per kg only a bit over 2x of LPG.

Possibly some simple compound that could be mass produced from syngas or some other single step scalable industrial process that is energy intensive, that is liquid at big temp range and possesses high energy density with very clean combustion would be an option in the future. Not sure what it would be, though.


That is indeed Kerosene in MJ/kg *and* MJ/liter which can be mass produced this way. Kerosene is 35MJ/liter and L H2 10MJ/liter.
A full A380 (do they still fly ?) with 180m3 fuel for a long haul flight would require 630m3 L H2 which should be cooled to -252C. 200C below the already -50C ambient temperature at cruise altitude. That extra 450m3 costs at least 20-30m of its fuselage length. sacrificing 200 of the 400 passenger space.
Admitted, 180m3 Jet A-1 weight 144 tons and 630m3 L H2 only 44 tons which saves 100 tons payload weight and hence less H2 fuel is required.
For smaller, still extensively used long haul planes like the A350 or B787 Dreamliner. the figures are smaller.
But anyway, it requires a stark fuselage (and wing?) design.

https://en.wikipedia.org/wiki/Energy_density#In_chemical_reactions_(oxidation)



[Edited on 2021-1-31 by metalresearcher]
View user's profile View All Posts By User
mysteriusbhoice
National Hazard
****




Posts: 301
Registered: 27-1-2016
Member Is Offline

Mood: A little above sanity...

[*] posted on 31-1-2021 at 12:33


produce the fuel using carbon capture and solar energy as the power source!!
View user's profile View All Posts By User
Fyndium
International Hazard
*****




Posts: 946
Registered: 12-7-2020
Location: Not in USA
Member Is Offline


[*] posted on 31-1-2021 at 13:05


There will probably be new energy storage technologies in the future that allow for a much higher energy densities than are known for now. Conceptually, as long as there is matter to manipulate, as in the atmosphere, only a source of energy would be needed to utilize (nitrogen, oxygen, etc) as a kinetic energy countermass.

In space, on the other hand, I don't know if they ever got the microwave engine to produce any thrust.
View user's profile View All Posts By User

  Go To Top