Viewing a single comment thread. View all comments

DrMux t1_je0x9x9 wrote

Reply to comment by Sagybagy in The Swiss hypersonic hydrogen jet aiming to fly between Europe and Australia in 4 hours by mancinedinburgh

It depends on how it's generated. There are a few methods, each with its benefits and drawbacks. These are referred to as the "colors" of hydrogen generation.

  • Green Hydrogen is produced by electrolysis. Obviously for this to be eco-friendly it needs to be powered by renewable sources - currently, as renewables are a growing sector, some argue that those sources would be better used for directly powering the grid, or other uses like carbon capture, etc. I'm not here to say which is actually the best use of renewables, just what some of the arguments are.

  • Blue Hydrogen and Grey (or brown or black) Hydrogen are produced from fossil fuel sources like natural gas (grey) or coal (brown/black). This process produces CO2 as a byproduct and can either be captured and sequestered (blue) or not (grey, brown, black).

  • Other methods include "turquoise" hydrogen which uses pyrolysis, and produces solid carbon which can easily be sequestered, and "pink" hydrogen which uses a nuclear power source to perform electrolysis.

EDIT: It may also be considered a bad fuel source because it needs to be stored at high pressure, which presents engineering challenges and can be dangerous (obviously, hydrogen is highly combustible. The Hindenburg used hydrogen to stay afloat and look how that worked out). I think there are also concerns about its energy density vs other fuel sources but I don't know as much about that.

14

Changleen t1_je39abs wrote

It doesn’t ‘need’ to be stored at high pressure at all. It just often is for convenience. Actually when under consideration for seasonal storage, using old salt mines or other mines with less permeable rock has been proposed and tested as a really cheap way to store a lot of H2.

4

Xeroque_Holmes t1_je4gfa6 wrote

> It doesn’t ‘need’ to be stored at high pressure at all.

Just to circle back to the original topic, in airplanes it does. Otherwise you won't have very much of it.

5

chatte__lunatique t1_je6ilsa wrote

To add, green hydrogen accounts for a very small percentage of hydrogen production. The majority (afaik) is black/brown hydrogen, with a a smaller amount of grey hydrogen. Green is like a percent or two.

1

Regnasam t1_je3yugg wrote

Crazy the lengths that people will go to to discount nuclear as a “green” power source.

0

Changleen t1_je42ap9 wrote

I’m not discounting nuclear at all, I particularly think these small modular reactors look amazing, and while we’re still talking fission rather than future fusion (let’s go!) then these molten salt reactor designs look great. They’re basically impossible to meltdown. Essentially the reaction situation is hard to maintain and any failure results in the reaction stopping rather than going critical. Good stuff. However it still comes with the problem of long (loooonnnnnggg) lasting radioactive waste. I can’t wait for fusion to get going.

3