[HN Gopher] Seawater split to produce green hydrogen
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Seawater split to produce green hydrogen
Author : tech2
Score : 26 points
Date : 2023-02-04 17:57 UTC (5 hours ago)
(HTM) web link (www.adelaide.edu.au)
(TXT) w3m dump (www.adelaide.edu.au)
| WithinReason wrote:
| _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?
| tech2 wrote:
| 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.
| phkahler wrote:
| Seems like a good first step in desalination.
| pixl97 wrote:
| 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.
| andrewflnr wrote:
| 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.
| Animats wrote:
| 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?
| andrewflnr wrote:
| 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.
| samtho wrote:
| 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.
| andrewflnr wrote:
| 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.
| andrewflnr wrote:
| 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
| ajb wrote:
| 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?
| arghnoname wrote:
| 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.
| [deleted]
| ben_w wrote:
| 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.
| LegitShady wrote:
| hydrogen is a power source, but green hydrogen isn't a power
| source.
| arghnoname wrote:
| 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.
| tarotuser wrote:
| 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
| refuse wrote:
| 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.
| thinkcontext wrote:
| 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?
| LarryMullins wrote:
| Both things are true. Green hydrogen is necessary for green
| fertilizer production, but green hydrogen for energy
| production is still a scam.
| skedaddle wrote:
| 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.
| vore wrote:
| 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.
| CharlesW wrote:
| Submission from yesterday (86 comments as I type this):
| https://news.ycombinator.com/item?id=34635111
| refuse wrote:
| 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.
| phkahler wrote:
| 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.
| beambot wrote:
| 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/
| MisterBastahrd wrote:
| What if we had a process to stabilize it? Say, mix it with
| carbon somehow....
| refuse wrote:
| 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.
| bobthepanda wrote:
| Right now, for planes and ships, it's either hydrogen or
| syngas, because batteries are too heavy.
| [deleted]
| dahfizz wrote:
| 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.
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