Seawater split to produce green hydrogen | Hacker News Reader

Seawater split to produce green hydrogen

adelaide.edu.au

59 pointstech254 comments

Submission from yesterday (86 comments as I type this): https://news.ycombinator.com/item?id=34635111

Another electrolyzer. It runs on unpurified seawater. But for how long? Where does the salt go? What is throughput like? How do they keep the thing from crudding up? And what happened with the last five promoted articles for new electrolyzers?

Don't know about the rest, but the salt can probably just stay dissolved. Their feedstock is cheap, costing a bit of pump electricity at worse, so I assume they can turn just a little bit of it into gas and toss the rest overboard.

You will quickly reach a max saturation unless you are letting water simply run through it. Regardless, the act of running water with impurities through any medium will result in deposits.

Just letting it run through, or otherwise cycling it really quickly and cheaply, does seem possible to me. I'd be interested to know if there are any fundamental reasons you can't let it flow, like if water moving past the electrodes decreases efficiency or something. You would at least need to watch out for the current taking away your product.

Deposits, yeah, but that alone doesn't sound like a showstopper. This is far from the first engineering application to use seawater, there are probably ideas out there that they can borrow.

I've always wondered how they prevent all the salts from reacting. Or what they do with side products.

If you run electricity through salty water, you tend to get a whole bunch of interesting chemistry happening.

There are products you can buy that perform electrolysis on water with a small bit of salt to make bleach (sodium hypochlorite).

If you bung in a shitload of salt, you eventually get sodium chlorate, or perchlorate forming, depending on the amount of amps you chuck in.

You also get chlorine coming off, etc...

You can kinda limit or control this with membranes, but with seawater you have a fuckload of side reactions that are going to happen.

>And what happened with the last five promoted articles for new electrolyzers?

I get the sentiment, and it’s one that comes up across a lot of cleantech articles. I think it feels like this because early stage stuff is often published by academics, but the next steps (where the technology ultimately dies or goes to market) are usually shrouded in NDAs and corporate secrecy.

We have split natural seawater into oxygen and hydrogen with nearly 100 per cent efficiency

What % efficiency does "nearly 100% efficiency" mean in this context?

I'd wondered the same, but even with that question hanging I think the outcome of being able to electrolyse sea water directly was interesting.

Seems like a good first step in desalination.

Seems more like a way to increase salination. Instead to me it sounds like a way to take solar and convert it into a hydrogen storage battery.

That is exactly what it does. This is a good thing. We can convert it into a fuel that can power vehicles and infrastructure. Yes, hydrogen is a scary element. Yes, hydrogen is hard to store. However, with water it is an abundant fuel source that should allow competition in conveyance and grid scale storage.

I read it as with exactly the same number of joules of electricity as the enthalpy of formation of the water they electrolyze (not sure about the terminology, it's been a while since I took chemistry). Basically the electricity supplies exactly enough energy to pop off the hydrogens.

The paper is being widely discussed everywhere. I didn't get it (paywalled), but it seems the high efficiency claim means that way more than 95% of the electrical current goes into electrolysis.

Overall, the most important thing is that this thing is cheap. Everything else you read around just means it's equal or not much worse than the usual electrodes.

Maybe one day we'll generate hydrogen with floating renewables in the ocean and just fill up a tanker to bring it to shore. It would make hydrogen a very attractive option for energy storage and transportation.

Hydrogen is a terribly dangerous thing to keep around for fuel. I've been in garages where fuel cell vehicles were being developed alongside EVs. They had hydrogen detectors and alarms. In case of leaks, evacuate. It has a very wide range of concentration where it will not just burn but explode. You don't want this in your neighbors garage.

It'd be great in a renewables-based grid for energy storage and transport. It could be carefully controlled and monitored because of the partial centralization. I'm not sure it'll ever make much sense for vehicles unless you could increase the density so it's stored as a slush without needing a high-pressure or an ultra low-temp holding tank.

Right now, for planes and ships, it’s either hydrogen or syngas, because batteries are too heavy.

You can't just put hydrogen in a tank like you can with i.e. propane. It's a real pain to deal with, and I don't think grid scale hydrogen will ever work out.

It would make more sense to use the hydrogen to synthesize methane, and then use that for grid scale storage and generation. This would be carbon neutral.

These are the types of conversations we need. So many people crap on hydrogen, but you can use it in a variety of ways. We can run cars on methane or convert it to ethanol. This makes converting our current fleet of vehicles cheaper and more realistic than converting to an all EV future. Even if we really, really wanted to move to EV, we can convert the existing fleet to carbon neutral ethanol for the next 50 years while slowly introducing EVs.

Electrocatalytic oxidation of methane to ethanol via NiO/Ni interface - https://www.sciencedirect.com/science/article/abs/pii/S09263...

Lesser-known, but there are solid-state hydrogen storage options that compare favorably to liquid storage (energetically, volumetrically, and inherently temperature & time stable). Best example is storing hydrogen in an aluminum matrix -- Aluminum Hydride, aka Alane. Companies like FuelX are commercializing.

https://en.wikipedia.org/wiki/Aluminium_hydride

https://fuelx.tech/

What if we had a process to stabilize it? Say, mix it with carbon somehow....

I mean it's not as if oil based fuels are good in that regard either.

From the abstract of the linked Nature article[0]:

> This is achieved by introducing a Lewis acid layer (for example, Cr2O3) on transition metal oxide catalysts to dynamically split water molecules and capture hydroxyl anions. Such in situ generated local alkalinity facilitates the kinetics of both electrode reactions and avoids chloride attack and precipitate formation on the electrodes.

For all the hype about "untreated seawater", I have to assume they're at least running it through a mesh to get the larger contaminants out.

[0] https://www.nature.com/articles/s41560-023-01195-x

Where are we going to use this hydrogen, that it would be cheaper than just using electricity directly?

Lots of people in the UK use methane gas for heating. This is cheaper than heating with electricity (using standard electric heaters).

There is talk of replacing the boilers with ones that can run off hydrogen. But even if the hydrogen is generated at 100% efficiency, surely it can be no cheaper than using the electricity directly, and since it won't be 100% efficient, it must be more expensive. And that's without taking into account the gain from using heat pumps, as opposed to directly creating heat.

The other main use of gas is to create electricity!

So where will this hydrogen be used?

Between about 2000 and 2010 I kept seeing people say "well actually hydrogen isn't a power source it's a just a storage mechanism", since about 2010 I keep seeing people say "oh we can't possibly get to 100% renewables, storage isn't a solved problem".

And back in the 80s and 90s, the US was regularly making 3.5 GWh hydrogen tanks fly hypersonic while attached to strong enough pumps that it could've powered an entire medium-sized European country for the 500 seconds it took to empty the tank, and they didn't bother to make them reusable.

So yeah, I recon it will be used for heating and power. Not 100% sure because it has competition from batteries, pumped hydro, and a global power grid, but it's certainly viable and the competition will take time.

Despite the many challenges, I like hydrogen as part of the solution to this stuff. It's easy to produce with commonly available inputs. If we had efficient central energy generation, it's a way of making that energy transportable. When burned (or used in a fuel cell) at the point of use, it burns clean.

I suspect the fears about its volatility are manageable. All concentrated forms of energy are dangerous. The issues with containing it and improving its density, I'm not sure. I'm glad we're not just 100% going with batteries. With all of these technologies there's a lot of ??? between here and panacea.

I just wish this attitude I see that this is an easy problem and we're going to invent our way out of the energy situation in a few years are a bit glib. The benefits of traditional energy forms are immense. The externalities can no longer be ignored, but we have an immense challenge to get even near parity in a general way. I think we'd do better to more soberly assess the situation.

Just to be clear, I'm agreeing with you, but there's a lot of untold story in how we get to the "it will be used for heating and power" bit.

hydrogen is a power source, but green hydrogen isn't a power source.

Your line of reasoning is the one I always take on these sorts of things. If it takes X input energy to make energy saving Y, if Y is not significantly more efficient than X, it's probably a net loss.

A lot of green stuff ends up being much less cheap/green if one looks at the total cost and environmental impact of the thing over its lifetime (including efficiency loss over time, mineral extraction, labor, electrical source, etc).

Energy has always been an expense people want to minimize. There's not a ton of low hanging fruit here.

Industrial chemistry. Steel making uses coke to reduce ore but could use hydrogen if it was cheap enough. Fertilizer like ammonia (NH3) is produced with those H's coming from methane, releasing carbon.

If it's nearly 100% efficient it becomes a low loss battery. Floating turbines could generate hydrogen in periods of low demand and send to a floating compressor and storage system to be used for energy generation or chemistry or airships, whatever

The country I live in is very small and has no natural resources. We rely on having oil shipped to us. From our point of view replacing oil with hydrogen would be an improvement. Due to various geopolitical and geographic issues relying on electric cables to supply us with power from our neighbors may not be a viable option.

Zepelins and rockets?

There’s a number of industrial processes that require higher temperatures than you can easily get from electricity. Replacing that with burning green hydrogen lets you decarbonize them.

Even if you can replace a furnace with an electric one, it may be easier and cheaper to replace a process burning gas with one burning hydrogen.

You can also use the hydrogen as a battery to move electricity into the future (with losses).

It is of course possible that there are better options for all of this other places, or that this process will not scale up well. And hydrogen has a lot of complicated logistics — storage and shipping are harder than larger gases. But a source of cheap green flammable gas has a bunch of potential applications.

The oxygen byproduct does not figure favorably unless it can more than pay for itself.

Seems like the same amount of electricity will always have more energy than the amount of hydrogen it can be turned into.

Takes theoretically a minimum of 39 kwh of electricity to make 1 kg of H2.

Decently efficient processes still use up 48 kwh so far to make 1 kg of H2 since they are not perfect.

1 kg H2 yields 120 to 140 MJ when burned

or probably the lower of 33 to 39 kwh depending on how you calculate the heat.

Keeping in mind the only way to get 39 kwh back out is if the byproduct oxygen actually consumed none of the electricity during the gas production.[0]

Probably quite a bit lower for domestic heating due to losses out of exhaust flues that are necessary.

Indoor heating using the same electricity will always be more efficient than turning the electricity to hydrogen first.

[0] didn't calculate that far myself to be sure.

Someone else mentioned ammonia, steel, and similar industrial chemistry applications, but another use case is transportation. I think regular ground transportation is going to mostly be battery electric eventually, but it's not really practical now to use batteries in planes except for narrow use cases. (Hydrogen has issues too, but they're probably not quite as difficult to solve.)

Ships also might use hydrogen as a fuel, if we can't find a better low-carbon alternative.

There isn't enough raw materials to power all of ground transportation with li-ion batteries. It is a matter of time before hydrogen or a derivative fuel like ammonia or e-fuels becomes the future of ground transportation.

I'd be willing to concede for the sake of argument that there aren't enough raw materials to replace all the world's combustion vehicles with EVs the way we currently do EVs. Almost certainly not if we keep using batteries high in nickel and cobalt.

I think what we should be doing instead is building EVs with modestly-sized batteries and focus instead on making charge stations more available and electrifying the major highways so that cars and trucks can travel long distance cross country without ever having to stop to charge.

The problem with hydrogen or ammonia is that, without some major technological advance, you lose a lot of energy in the process of making the fuel, transporting it, and converting it back into kinetic energy either in a combustion engine or fuel cell/motor. If you can synthesize the fuel with solar power but only 30% or 40% actually ends up doing useful work, then it's far less efficient than using batteries and electric drive trains, which might be somewhere around 80% when you factor in transmission losses, charging inefficiencies, motor inefficiencies, and so on.

Maybe some day we'll have so much energy we don't know what to do with it, but I think current events are pointing more in the direction of energy getting more expensive rather than cheaper, and whatever means of locomotion requires the least energy will be the one the masses use if it's reasonably affordable.

If something is nearly 100% efficient, how can anything else be significantly more cost effective?

Because the 100% efficient part is one step, and we are evaluating the whole process.

That sounds like a cop out. The article specifical mentions low cost catalysts. There doesn't sound like there is any credible argument for the whole process being always expensive.

Can we please stop adding colors to elements? It's silly and very awful marketing. I'm pretty sure that last I looked, hydrogen is transparent in gas form.

So are there strange quarks?

Well, the proper color for anything hydrogen is "shadow" because all mass market placement of "hydrogen" is the oil industry trying to delay the onset of EVs and alternative energy.

Don't get me wrong, there is legitimate scientific aspects to green/blue/black classification, but those don't matter, because what is being discussed here is in the fantasy land of news media. Anything "green" or "blue" in hydrogen is something far off in the future and they will use fossil fuels in the "short" run. Almost like, it is an "aspirational" green power source. Green, as in, someday theoretically it can be green.

For SPECIFIC industrial use cases, I welcome hydrogen as a possible step off of fossil fuels, you know, someday. Fertilizer, steel, etc. And I like the discussion of reusing existing natural gas turbines and other equipment but... anyway, don't get your hopes up.

They tipped their hand with the "100%" figure. Hey guys, look, we violated the basic laws of thermodynamics! That's why the reporting on hydrogen is so hair-pulling, everything is smoke and mirrors and obfuscation and fake numbers and miracle technologies, so even where there is legitimate potential and uses, I completely distrust it.

I mean, I have to go to goddamn reddit to get a discussion of the "100%" figure:

https://www.reddit.com/r/science/comments/10rvo8x/comment/j6...

100% is for Faradaic efficiency.

"Faradaic efficiency only looks at the efficiency of charge transfer and is not the same as the energy conversion efficiency. The latter is usually meant when speaking of "efficiency" of hydrogen production and it will likely still be ~60% for this new process.

Fucking ridiculous.

TLDR The title is highly misleading."

Fuck your latest "magic hydrogen technology" of the day.

There is no such thing as "Green hydrogen", other than the facade of oil companies that created that term to allay climate change fears. And we even have a term for this - Greenwashing.

https://theecologist.org/2020/dec/18/hydrogen-hoax

I'd say overall that hydrogen is an attractive proposition because once you have the infra for it, you can substitute whatever color of hydrogen you want. The trick will be making sure we can easily replace gray hydrogen in the future for green.

Millions of tons of hydrogen will be necessary for fertilizer production and other industrial processes for the foreseeable future. If this hydrogen is produced using electricity from no carbon sources, what would your objections be? What do oil companies have to do with hydrogen not derived from any of their products?

Both things are true. Green hydrogen is necessary for green fertilizer production, but green hydrogen for energy production is still a scam.

There's no way to ship solar or hydro energy. And for shipping everything else -- how would you power a boat from India to the US? Or a plane? Hydrogen remains the only green (ish) game in town for these needs.

Methanol produced using green energy is much better alternative to hydrogen. It is vastly easier to handle and store.

Methanol would be made from hydrogen. It is functionally just another way of storing it.

Who mentioned green hydrogen for energy production?

It's at least a possible grid scale storage solution.

If you make ethanol from freely available hydrogen, you can convert the existing fleets (basically anything after like 2000 should be able to run ethanol with some hose and seal replacements). This is dramatically cheaper than telling the poor and middle class, "Let them by EVs (which cost a small mortgage)."

Pray tell, what would the price of ethanol produced from green hydrogen be? The processes I've seen are either bio or electric with a catalyst but they are just at the science project stage, no where close to being scaled up.

> This is dramatically cheaper than telling the poor and middle class, "Let them by EVs (which cost a small mortgage)."

The 2023 Chevy Bolt has a list price of $26K before the subsidy. Tesla Model 3 is $43K before subsidy. The average price paid for a new car in 2022 was $50K. Of course no one is forcing the poor and middle class (or anyone else) to buy EVs. Most of them by used cars anyway, that market is definitely not mature yet, though the new subsidy can now be applied to used models.

Even before the price war which has just broken out most mainstream industry analysts were predicting upfront, nonsubsidized price parity of like EV and ICE models mid to late this decade. That's on top of the significantly lower fuel and maintenance costs and of course the subsidies.

The article contradicts your point but justifies itself by just handwaving over it:

> So called green hydrogen has its own problems. Yes, it is technically possible to use renewably-produced electricity to electrolyse water, to make hydrogen – but you need a huge amount of electricity to produce a small amount of hydrogen.

If we can improve the efficiency of electrolysis production of hydrogen, then I don't see how it's greenwashing if it's possible to produce hydrogen without carbon.

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