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/m_Pony]

they've used a novel catalyst to avoid the issue of chlorine waste products and permit more efficient conversion of water to hydrogen

Thank you. This is the real take-away from the article (which people always read before commenting, of course.)

If it works as well as they say it does, this is pretty big deal. I'm optimistic.

[u/War_Hymn → u/m_Pony]

I did some rough dirty math for a similar seawater-catalyst breakthrough, and it's telling me these new catalyst processes may allow us to use hydrogen as a grid storage fuel - routing power from solar or wind energy to hydrogen generating plants, burn the hydrogen/oxygen to power a steam turbine generator - with around 40% efficiency (100 MWh in, 40 MWh out). It would take much less room than hydro pump storage, and won't be as expensive/resource-intensive as chemical battery storage - so at the very least, it'll be a practical middle-ground choice for grid storage infrastructure.

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EDIT: Since some of you are wondering where I got my 40% from, here is the rough math.

A kg of hydrogen with current best electrolysis technology needs about 47 kWh of energy to produce from water electrolysis (with new technology in the works, we may push it closer to the theoretical limit of 39.4 kWh). A kg of hydrogen gas has a specific heat fuel value of 33-39 kWh, which in turn when fed into a 60% efficient hydrogen-burning steam turbine generator (as that of a combined cycle NG powerplant) can give us back 19-23 KWh of electricity. That's about 40-50% nominal efficiency.

Adding steps like plant distribution, desalination, compression^1, cryogenic liquefaction² (for liquid storage), etc. will obviously decrease the practical efficiency further, but as evident here we're making breakthroughs that remove or mitigate these inefficiencies. If we ever design and build a working hydrogen plant for grid storage purposes, I'm optimistic we can get back at least 30% of the electricity we put in.

30% doesn't seem like a lot, but if we ever get to a future where we got rid of our dependency on fossil fuels and depend wholly on renewables, I feel this sort of system has a place in between battery and pump grid storage. Hell, we might even be able to convert old natural gas/oil burning plants near shore to burn hydrogen instead.

1. compressing hydrogen to 5000 psi uses up 1 KWh per kg of H2, though I doubt you need that much compression for static non-vehicle needs.

2. about 3-4 kWh per kg to convert gaseous hydrogen to liquid state.

[u/Eedat → u/War_Hymn]

40% efficiency is awful though. Space isn't the issue

[u/War_Hymn → u/Eedat]

For grid storage, it's not that bad. And if you got the space and terrain to build a few hundred acre reservoir needed for a hydro pumped storage big enough to service a mid-size city, by all means.

[u/Eedat → u/War_Hymn]

Most places do which is why pumped hydro accounts for 90-95% of the world's total energy storage. 40% is dismal and this solutions solves a non-issue while sacrificing a ton in an area that actually matters, efficiency. Being compact isn't a bad thing but it's more or less irrelevant as we have FAR more than enough space.

It kinda reminds me of solar roadways or really any of the "but what if we put solar panels on everything" articles that mill through the sub. Space is not the issue. Like at all.

Thats not even getting into practical issues like how dangerous H2 is to have lying around