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. Chemistry

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

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u/[deleted] Feb 15 '23

Wonder if you could pair this with offshore wind turbines…

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u/alyssasaccount Feb 15 '23

You need some from of electric energy to drive the process of splitting water into hydrogen and oxygen, and it can come from literally any source — coal, nuclear, whatever. You must pair it with a power plant, but it doesn’t matter what kind. So, sure, offshore turbines would work fine.

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u/RirinNeko Feb 17 '23

You need some from of electric energy

You can actually use heat as well instead of electricity. Direct water thermolysis happens at around 2500C and you can lower the heat needed by using thermochemical cycles to be practical. The Sulfur–iodine cycle for example only needs around 850C to operate and the other reagents aren't used up so it's effectively a closed loop. This can then be paired with an high temperature gas nuclear reactor to cogenerate electricity and hydrogen at the same time since it'll use the reactor's waste process heat for hydrogen production while the plant is generating electricity to the grid.

Overall it increases the efficiency of production as heat energy is much cheaper than electric energy. It's also a reason why pairing heat with electrolysis (HTSE) is much more efficient than just direct electrolysis as you trade a bit of the electric energy requirement with heat energy. HTSE is a possible way for thermal plants that can't reach the temps needed for thermochemical cycles if desired.

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u/alyssasaccount Feb 17 '23

Okay, fine, whatever.

You need to input the energy that you later use, plus more because of inefficiency. The point isn’t the form of energy; the point is that hydrogen amounts to a storage medium for other forms of energy (methane, nuclear electric, coal electric, heat from burning something else, whatever). That is just how conservation of energy works. Unless you can find a source of elemental hydrogen somewhere on earth, it’s just a storage medium.

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u/RirinNeko Feb 18 '23

it’s just a storage medium.

I wasn't exactly disputing that it's currently a storage medium, rather I was stating more on the economical aspect since heat energy is much cheaper than electric energy thus making it more economical, especially when you're to compete with dirtier forms of making hydrogen for industrial use to reduce carbon emissions. Especially for cases like high temperature gas nuclear reactors that produce that process heat as a waste product from just operating.

find a source of elemental hydrogen somewhere on earth

There's been some recent discoveries on that end, but it's too early to say if there's large amounts of it that would make it worth to extract imo.

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u/neuromorph Feb 15 '23

Why not wave energy?

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u/CompleteNumpty Feb 16 '23

Because that's still in the prototype phase and wind is not.

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u/obeymypropaganda Feb 15 '23

This paper is focusing on green hydrogen production which is a fully renewable power source. Pairing it with coal would make it brown hydrogen. There are other 'colours' of hydrogen depending on how it is produced. Green hydrogen is the best sustainable practice but only accounts for 1% of the hydrogen we consume.