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Comment by pjc50 | Hacker News Reader

So apart from the clickbait, the reason why this is interesting is because it's a limiter for the often cited idea of clean green hydrogen from electrolyis. The current use of titanium and precious metals is, obviously, really expensive, so it's uneconomical to build something that only runs on "spare" electricity.

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I don't think the efficiency or longevity of electrolysis equipment is the limiting factor...

The limiting factor is that natural gas is very cheap and cracking it to make blue hydrogen is really easy at scale, and gives off CO2 which is useful for injection into wells to increase production. That sets a price ceiling of hydrogen.

At the other end of the scale, there are batteries to store 'free' electricity and resell later. That sets a floor price of electricity.

Between the floor price of the input and ceiling price of the output, there is no room for electrolysis, even at 100% efficiency, unless government policies mandate it or restrict batteries or blue hydrogen.

There's one case, rural areas often have abundant energy sources (hydro, wind,etc) but few consumers, in Northern Sweden f.ex. a lot is produced but there's a lot of losses in transporting the energy south.

Now, yes, as long as natural gas is cheap(inbetween US or Soviet wars) it'll probably be the core for hydrogen, however batteries won't help much in the north since the transmission rather than usage is the cap even with batteries so excess production could be redirected towards hydrogen production.

If solar continues to plummet in cost we may see distributed industry in rural areas, to take advantage of energy that is essentially stranded by transmission cost. Storage becomes even more important in this scenario.

Well, unless all the planned datacentres get built, using more electricity than some small countries.

The blockage of connecting those to the grid will encourage self-generation, which will mean putting them off in the boondocks where land is cheap. Taking that to the logical limit is where space data centers come from.

I think we're going to see a repurposing of remote coal-fired plants with renewable stored heat. The Four Corners plant, perhaps? It's supposed to stop operating in 2031, I believe.

In the US, this will never happen due to NIMBY zoning laws.

Most rural areas have pretty permissive zoning.

But also, other than Texas, I don't hear about a lot of regional over production. There's pretty good interconnection within and between the two major grids.

One reason you don't see overproduction is it's hard to get connected to grids. Local self-generation eliminates that roadblock. I think we're going to see increasing energy autarky in rural regions as solar gets cheaper.

Assuming ultra low cost thermal storage becomes a thing, there's going to be a market for small externally heated engines to recover that heat as power. That (+ batteries) will enable complete off-grid operation with PV at small (maybe 100 kW) commercial scale and larger.

China has this in a big way. The big energy sources are mostly in northwest China, and the big loads are in the southeast. That's why China leads in million-volt DC power transmission.

Sometimes the price of natural gas is even negative, there is too much of it.

"Natural gas at Texas’s Waha hub is trading at negative $7.05 per million British Thermal Units, hitting a record low of negative $9.52 on April 15."

https://www.barrons.com/articles/natural-gas-texas-negative-...

There are different kinds of water electrolysis equipment, with different capital expenditure and operating expenses.

"Alkaline electrolyzers are cheaper in terms of investment (they generally use nickel catalysts), but least efficient. PEM electrolyzers are more expensive (they generally use expensive platinum-group metal catalysts) but are more efficient and can operate at higher current densities, and can, therefore, be possibly cheaper if the hydrogen production is large enough."

https://en.wikipedia.org/wiki/Electrolysis_of_water#Efficien...

Anything using platinum-group metals will be very expensive. Therefor catalytic converters in cars use very little platinum-group metals.

"The amount of palladium in a converter can vary, but it is typically around 2-7 grams." https://vehiclefreak.com/how-much-palladium-is-in-a-catalyti...

> Sometimes the price of natural gas is even negative, there is too much of it.

Googling that tells me there was/is too much of it locally.

The gas is a byproduct of drilling for oil, and there was/is insufficient pipeline capacity to move it to consumers.

That's what happens when the storage tanks fill up. Nobody can buy it because they have to accept delivery and put it somewhere.

Reducing the capital cost of electrolysis is extremely good, because it makes plants that only produce when electricity is cheap (midday in sunny climes, when wind is blowing in the Nordics) more feasible.

If this works out at scale (lots of problems can be found between a lab discovery and mass production), this is legitimately a very good thing for renewables.

> unless government policies mandate it or restrict batteries or blue hydrogen

Yes, but I think this the most likely outcome. Natural gas is only cheap in certain areas, and the past few years have made everyone very, very aware of the geopolitics involved in getting hold of it. While global warming is not going away, and I question the extent to which CCS actually happens with blue hydrogen.

Batteries are capital equipment in the same way as electrolysers are. They're great at short term storage, but medium-term is still a bit more of an issue. "Restrict batteries" is obviously not on the table except for stupid retail corner cases where utilities have captured the regulator.

There's a potential market for lots of green H2 in Haber nitrogen, metals refining, and synthetic jet fuel etc, but only if the cheap CO2 emitting option is priced out or banned, or H2 electrolysers get comparable capital prices to battery storage.

With CO2 emitting option is priced out or banned, direct hydrogen production using high temperature sulfur–iodine cycle without H2 electrolysers could be economic option. The heat could be supplied from high temperature nuclear reactor.

How to make hydrogen production cheaper and easier: include an atomic reactor component.

Huh?

I’d be interested in hearing about some scenario where this actually costs less, given the cost of building anything nuclear in 2026.

I agree, the experience building nuclear reactors is mixed bag. Some builds failed, like Flamanville 3, Hinkley Point C, Vogtle 3. Some builds succeeded: Barakah nuclear power plant, Fuqing 5,6. It really depends on maturity of supply line and political support.

The real question is: how do we produce hydrogen from the coming massive overbuilding of cheap-but-variable solar. Nuclear reactors are a whole different animal: even if we build them "cheaply" they're not going to approach the costs of overbuilt solar, so those nuclear watts will be better used for other purposes.

Coupling PV to electrolyzers and efficient hydrogen production using solar energy is still open research problem. Batteries will be probably needed.

"The low efficiency of PV-electrolyzer systems can be attributed to several factors: intrinsic losses in both the PV and electrolyzer units, energy consumption by balance-of-system components (e.g., inverters, thermal management), and, most critically, ineffective electrical coupling. Although some researchers advocate for direct coupling as a cost-effective solution, variable solar input remains a major challenge. Fluctuations in solar irradiance can cause the power delivered to fall outside the acceptable operating range of electrolyzers, leading to frequent shut-downs and start-ups. These cycling events can accelerate degradation, particularly in PEM electrolyzers, and also affect the purity and yield of hydrogen"

"Recent studies also highlight the integration of battery energy storage systems (BESS) into large-scale PV-CSP hybrid plants as a strategic enhancement. With anticipated declines in battery costs, this integrated approach may become increasingly viable in the near future."

https://link.springer.com/article/10.1007/s44373-025-00080-4

Processes that involve heating sulfuric acid vapor to decomposition don't sound terribly practical. If you thought seawater corrosion was challenging...

Back to the corrosion discussion from the original article: when handling sulphuric acid at 800C, what kind of piping material do you need?

Glass coated steel, silicon carbide.

"Material selection, simulation, and experimentation of sulfuric acid decomposition in a pilot-scale sulfur-iodine thermochemical cycle for hydrogen production"

https://www.sciencedirect.com/science/article/abs/pii/S00162...

> With CO2 emitting option is priced out or banned

GP was talking about injecting the CO2 back into the well, not releasing it to the environment. There are even standards for specific injection wells used for long term storage (EPA Class VI).

When would that ever make sense over solar?

With solar sometimes producing a lot of energy when you don't need it or can't store it, having a cheap hardware to produce hydrogen from it is quite nice.

Natural gaz may be cheap, but you can't beat free.

For this setup, the price of the hardware was a limiting factor.

As always, the question is not "do this for solar, or not?". The question is, "Is this a valuable & efficient way to store energy?".

It has to compete with pumped weight (usually water), pumped heat (salt, water, or underground), electric batteries, and so on.

So, as always, it's complicated.

I would say your question needs to be expanded to "Is this a valuable & efficient way to store energy which can be scaled to any location?". The pumped options aren't. Batteries are cost-effective for time-of-day shifting, but not long term. Electrolysis and gas tank storage can be built in any climate, any terrain. Then benefit from economies of scale while the others are stuck in niches.

Even without natural gas, hydrogen as a general energy storage medium competes against thermal storage. The round trip for this (electrical energy back to electrical energy) can be as good as hydrogen, and the storage medium can be literally dirt cheap, cheap enough that seasonal storage looks like it makes sense, if the design is brutally focused on cost optimization.

Here, corrosion of steel is also part of the problem, as you are burying steel pipes in piles of hot dirt.

> The limiting factor is that natural gas is very cheap and cracking it to ...

Another, or perhaps related, limiting factor is just how difficult hydrogen is to handle safely - compared to natural gas, batteries, or other alternatives - https://en.wikipedia.org/wiki/Hydrogen_safety. And it does not take many surprise explosions & fires to give a technology a bad rep. Especially when people feel there are obviously-safer alternatives.

Hydrogen is used as feedstock for many industrial processes, but also converting it to methanol should be the way to go for seasonal storage, but getting cost-effective hydrogen is the harder step.

One interesting use is hydrogen to feed microbes. The driver potentially is solar panels produce 30-100 times more energy an acre than corn. So what if you use solar to produce hydrogen to feed microbes which then produce various feed stocks using nitrogen and CO2 from the air.

Yes, although I'd still want to see how much of total delivered hydrogen cost this actually moves

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