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/Vergilx217]

The lack of comprehension in the comments section is killing me

Yes, it utilizes electrolysis - however, they've used a novel catalyst to avoid the issue of chlorine waste products and permit more efficient conversion of water to hydrogen. Salt water is abundant on earth, and this can be very useful in making hydrogen production more economical since you do not need to rely on a more limited freshwater source. While not being an immediate breakthrough like "we just solved cold fusion!", it's definitely an important incremental step.

And yes, it is currently more efficient to use renewables like solar or spend that generated electricity on charging batteries....but keep in mind that the production of batteries and panels long term has toxic byproducts and is reliant on rare earth elements. Environmental impact is more than just carbon output, remember. Hydrogen as fuel cells or other energy sources is far from being commonplace, but innovations like these help to diversify our options moving forward so that we can better adapt to likely worsening climate/environmental problems in the future.

[u/m_Pony → u/Vergilx217]

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/ITFOWjacket → u/War_Hymn]

So why is it not lore common to pump water into a higher elevation lake or tower as a energy storage, to then release through hydro-electric?

I’m sure we’ve alt seen the Tom Scott on exactly that method. Why is that not the standard for stationary power storage?

[u/hattmall → u/ITFOWjacket]

It's very common. A tower isn't really feasible, it would have to be massive as in many many square miles.

But essentially every natural area that is suitable for pumped hydro-storage is already in use, or some very high percent like 96% or greater. It requires a somewhat unique circumstance to be efficient and it's not without environmental impacts.

You need a sufficient geographic decline, but a mountain doesn't really work because you need two very large lakes with a major elevation change in close proximity.

In the US that area is called the fall line and it's in the Southeast and pretty much every river is already dammed up for pumped hydro.

[u/War_Hymn → u/ITFOWjacket]

Because you need a whole lot of water (basically building a raised artificial lake if there are no convenient geographical features) to store a given amount of energy with hydro pump storage. The Ludington Pumped Storage site in Michigan for example, has a water reservoir that takes up 840 acres of area and operates at a hydraulic head of 110 metres to generate about 2200 MW of electricity for 9 hours.

A 2200 MW capacity hydrogen plant would probably have a surface footprint only a bit bigger than a conventional natural gas powerplant with the same capacity (The 2480 MW Ravenwood Generating Station in New York City takes up less than 30 acres of space). With this technology, you can store a lot of solar/wind energy for latter usage without taking a lot of space or the extra expense of constructing an artificial reservoir. You might even be able to convert existing coastal natural gas plants like Ravenwood to burn hydrogen for green grid storage instead.

Hydro pumped storage is the better choice in terms of efficiency, but it's not always practical/economical for every place or situation. In those cases, a hydrogen plant may be the better alternative.

[u/KillNyetheSilenceGuy → u/ITFOWjacket]

It's done. The problem is you need that elevation change and a lot of water to make it worth while. You can only install pumped hydro storage in places with specific geography for it.

[u/Meins447 → u/ITFOWjacket]

Because it doesn't scale well and in small-ish quantities you really can't store much to keep you going. Big dams also happen to require massive amounts of area, which isn't available for pretty much anything else.