How to make hydrogen straight from seawater – no desalination required. The new method from researchers splits the seawater directly into hydrogen and oxygen – skipping the need for desalination and its associated cost, energy consumption and carbon emissions.

[u/Wagamaga]

https://www.rmit.edu.au/news/media-releases-and-expert-comments/2023/feb/hydrogen-seawater

[u/mojitz]

Hydrogen always struck me as an excellent fuel source in a world in which we have achieved a massive clean energy surplus — say following a fusion breakthrough. At that point you can just dump energy into electrolysis for an energy storage medium that doesn't really require any special minerals or anything. Hell, you can even burn it in a combustion engine (or even a rocket) and the output will still be carbon neutral.

[u/mojitz → u/[deleted]]

I had always assumed that there would be some serious production capacity challenges to this, but if not then yeah that sounds pretty reasonable. The one hard downside seems to me to be the local air pollution inherent to burning hydrocarbons, but we seem to be able to get that down to reasonably acceptable levels for the most part.

[u/Luemas91 → u/mojitz]

Using atmospheric carbon as a carbon source for manufactured hydrocarbons is so unbelievably expensive, to see someone suggest it unironically boggles the mind. Maybe carbon Capture will get more efficient in the future, but something like 250 g of carbon costs a 1.10 in electricity to extract, before you go into all the steps that would be required to convert the carbon dioxide into a methane, methanol, or some other efuel.

Your initial impression is correct; hydrogen production is going to be very intensive, which is why any rules about green hydrogen production will require strict rules about additionality to prevent additional CO2 emissions from occuring. The main uses are likely to be chemical and the fertilizer industry, as energetic purposes, the future cost is not likely to be low enough for the average person to want to use a hydrogen car, and maybe for some long duration storage in grid Energy.

Someone earlier mentioned 40% round trip efficiency for hydrogen storage, which is much worse than compressed air even. At an optimistic 50 $/MWh of input electricity, that means the hydrogen would only make sense to burn at 120 $/MWh. This gets worse if say electricity in the medium to long term costs 130 euros/MWh like in Europe.

[u/Luemas91 → u/[deleted]]

Right. In fairy tale land everyone shits rainbows and farts electricity, and has no problems.

[u/Talinoth → u/Luemas91]

I mean, economically viable fusion is merely very hard/faraway, not necessarily "science fantasy".

Of course, before shitting on you for missing the point of the entire comment thread, I'll admit (mostly) all of our infrastructural and climate change problems disappear almost overnight if we have an extremely cheap energy source like viable fusion.

That sounds like an overstatement, but I do think almost every problem we have now in the world other than war - food, clean drinking water, productivity, infrastructure - is solved by having an ultra-cheap energy source.

So being flippant isn't entirely unjustified. After all, if you had enough energy to desalinate water for 100 billion people and not break a sweat even with only 8 billion people on the planet, you're then in a post-scarcity world for all intents and purposes.

And that really does feel like a fairytale right now, viable or not.

[u/Just_wanna_talk → u/[deleted]]

A big issue with burning hydrocarbons though, even if you manage a carbon neutral process, if there's still a large impact on human health since most of that will be burning in industrial areas and city centres creating smog and fine particles in the air we breath.

[u/[deleted] → u/mojitz]

The Hindenburg enters the chat.

[u/googlemehard → u/mojitz]

Burning hydrogen in the presence of mixed gases like those found in air does create some pollution due to high temperature.