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haircut50cents t1_iy8pwaq wrote

This will be an unpopular opinion but that's okay.

I wish they would stop spending time on hydrogen. The energy density is so low unless you turn it into "slush" which takes an incredible amount of energy to do and becomes a really dangerous fuel. I worked on these projects at a fairly large industrial company.

It just doesn't work but governments pay for it to appease environmentalists and businesses happily take the money. They all know it's not the future.


Fearlessleader85 t1_iy91spo wrote

For airplanes, the energy intensive nature of it doesn't matter quite so much. We can produce it on the ground using alternatives, but up in the air is where energy density matters, both per unit volume and mass. Hydrogen has mass energy density in spades, which does matter.

There's definitely some barriers, but if we can get it to work, it opens some massive doors for fighting climate change.

It's possible, even likely, that an algae based biofuel could be a lower hanging fruit, but before that gets to be carbon neutral, it has to scale to support the full supply chain. Hydrogen doesn't have that limit. We could produce it cleanly, even with non-firm power options like solar and wind. Then from day one, it's carbon neutral.


haircut50cents t1_iy9crlr wrote

Hydrogen is great per mass but horrible per volume. That's why it has to be cooled down past liquid into slush. Even then the tanks needed are enormous compared to jet fuel used now. Would require a complete redesign of airplanes - maybe larger lifting body aircraft or flying wings.

That would require a more space at airports. Maybe the supply chain is there but rebuilding all the worlds airports? That's a mess.

I do like biofuels because of the mass and volume energy storage and they drop into the supply chain really well.

The best way to stay carbon neutral is always to not build new stuff to replace working stuff. True for cars and I would bet even more so for airplanes.

Interesting discussion though, thank you!


Fearlessleader85 t1_iy9e3g8 wrote

I was also thinking of much larger lifting bodies, like flying wings. I don't think you'd need to rebuild airports completely, but renovations would for sure be needed. But in that change, you could get some significant benefits, like higher altitude flights with greater ease.

But i disagree with your claim of reusing things rather than building new. For most things like cars, the carbon use of the fuel or energy quickly outstrips the corbon footprint of production. So, continuing to use that refrigerator from 1956 that keeps on chugging is churning out more carbon every few years than building a new fridge. Replacing a car that gets 20 mpg with a new one that gets 30-35 mpg has a very rapid "carbon payback".

If efficiency is more or less constant, sure, keep using the old thing as long as possible. If new versions produce significant improvements, replacement is the best option. The math for these decisions isn't that complex.


KingRBPII t1_iy9bn6c wrote

What else can you use?


CurtisLeow t1_iy9eii4 wrote

Natural gas is substantially more dense, easier to store, and can be produce from carbon neutral sources.


Why_You_Mad_ t1_iy9wgb3 wrote

Natural gas is just another hydrocarbon. lol. Why even switch from jet fuel?


horsemagicians t1_iyahxbu wrote

Well if we’re only going to talk about jet fuel vs natural gas, natural gas burns far more cleanly.


CurtisLeow t1_iya1bbi wrote

Kerosene can't be produced from carbon neutral sources. Kerosene produces soot. Natural gas-powered aircraft are already a thing, by the way. It's a more common fuel than hydrogen.


Why_You_Mad_ t1_iya1r2g wrote

As soon as you burn it you're just dumping more CO2 and CO into the atmosphere. How could it possibly be carbon neutral to burn more hydrocarbons?


CurtisLeow t1_iya98j1 wrote

Because there are both fossil sources and renewable sources of natural gas. That's why it's called natural gas. You produce natural gas. Waste treatment plants produce natural gas. Sabatier reactors produce natural gas. There are multiple carbon neutral sources of natural gas.


Prophet_of_Entropy t1_iydgwfw wrote

you can synthesize methane, aka natural gas, make it from atmospheric carbon and hydrogen, but that would be incredibly energy intensive and only viable if we crack efficient fusion electricity.


Cpt_Soban t1_iybehb4 wrote

So... Fossil fuels lmao


CurtisLeow t1_iybmdzp wrote

Fossil fuels are fossil deposits. Some natural gas comes from fossil deposits. There are renewable sources of natural gas, just like there are renewable sources of hydrogen. Although currently most natural gas, and most hydrogen comes from fossil deposits. Most hydrogen isn’t carbon neutral either.


Cpt_Soban t1_iyburr3 wrote

Lol natural gas is fossil fuels mate. You burn it for energy which creates carbon.

Try again.


CurtisLeow t1_iybuybe wrote

I literally linked a Department of Energy article on renewable natural gas.


Cpt_Soban t1_iybw7u8 wrote

You understand we need to move away from carbon emitting energy right?


CurtisLeow t1_iybwccr wrote

And by that standard, hydrogen isn’t carbon neutral either. The vast majority of hydrogen comes from natural gas, as shown in the other Department of Energy article I linked.


Cpt_Soban t1_iyc27dl wrote

It's still better using hydrogen derived from fossil fuels from the grid, than burning fossil fuel gas after extracting gas from fossil fuel, then burning it as a fossil fuel.

The net benefit is fewer carbon emissions using hydrogen, with improvements later as the grid transitions.

As I said: we need to transition AWAY from carbon emitting energy.


Ericus1 t1_iyas72s wrote

Fully synthetic fossil fuels using green energy to manufacture. Still massively energy intensive, would need the same hydrogen as a feedstock, but vastly safer, more stable, uses existing infrastructure, and would be carbon neutral.


Drak_is_Right t1_iyaen14 wrote

In the future we very well might manufacture jet fuel from water and air To continue fueling our planes


Ericus1 t1_iydbezv wrote

Environmentalists are not the ones pushing for hydrogen. Look at who actually is pushing it and funding lobbying groups behind it - it's the natgas/fossil fuels industries, desperately trying to push something they can produce and control into these sectors. Same as with heating, other areas of transportation, and storage.