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Having seen too many such announcements about promising green technologies, I tend to ask a few questions when seeing something like this. One of them is what state a technology is in (early research, announcement, small prototype, industrial scale prototype).

It is not really clear from the article what the scale and state of this technology is, but at least from the pictures this looks like small and very early stages. It's of course a good thing to do early research, but already pitching that with claims about it being "cheap" sounds dishonest if you're far away from a working, industrial-scale prototype.

COVID saw some interesting procedral changes - massive industrial scale parallelism.

Multiple candidates were developed and trialled in parallel with ramping out mass production, storage and shipping.

Some of this was wasted effort, some of it was useful regardless of which candidates made the final vaccine cut.

The end result was dramatically compressed rollout times.

Right now the world has a billionare or two with negotiated contracts to deliver green (not blue) hydrogen (eg: to Germany) at a scale that significantly increases world hydrogen production within a 5-10 year time frame.

Already the industrial elements are being built for transport, end use, power collection sites, etc.

This activity makes the possibily of dropping in better methods of hydrogen spliting as they are developed feasible in a shorter time frame than otherwise thought possible.

Unless it says otherwise, it's generally safe to assume that an article put out of a university is in the early research phase.
Is hydrogen cheap to transport, cheap to store, and cheap to use though? I thought making it was only a small part of the problems with hydrogen.
Hydrogen is a small slippery hard to contain gas molecule.

Ammonia transport and storage is far more likely.

Hydrogen is not at all hard to contain. Just put it in a gas bottle. The real issue is the very low density which makes the tanks rather large.
Then why do the actual people who work with hydrogen worry about transport losses if you just need a thick enough tank?

In Michael Liebreich’s Keynote Speech at World Hydrogen Congress 2022[0] he speaks about the problems of shipping hydrogen. you get around 1% of loss PER DAY (0.1% for LNG). And because of the huge tanks the energy capacity is 1/4 of a comparable LNG carrier. The economics just don't make sense.

[0] Michael Liebreich’s Keynote Speech at World Hydrogen Congress 2022 (16:00 mark about)

The talk is about liquefied gas. Bottled gas has way too low density to put it on a tanker. The losses are due to boil-off, not due to leakage.
In gas form, hydrogen is much worse. You need about 18 truckloads of hydrogen stored at 200 bar to match a single truck load of diesel in terms of energy.
You can also use certain oils to absorb (not sure if that is the technical correct term here) the hydrogen for transport. Renders it inert, no losses and it doesn't even count as dangerous goods for land and sea freight. Seems to be pretty easy to get the H2 out of the oil for use or transfer.
The man in the keynote I linked was "Michael Liebreich, Chairman and CEO of Liebreich Associates, through which he provides advisory services and speaks on clean energy and transportation, smart infrastructure, technology, climate finance and sustainable development. In September 2020, he became an official adviser to the UK’s Board of Trade".

...and he didn't know of any better ways of transporting H2 than liquid form.

If it would be "pretty easy" to absorb it to oils, I'm sure that would've been tried already.

the industry's goal seems to be hydrogen->ammonia - transport - ammonia->hydrogen, because ammonia is orders of magnitude easier to transport.

Just before Covid I did consulting for a green hydrogen product, on logistics, supply chain and all that. And, in the low to mid volumes, the easiest way, which included distribution to smaller sites, was using carrier oil and standard oil tank containers. I would have to look the exact oil up again.

Also true, as soon as one hits high volumes nothing beats liquified gas or pipelines.

> Just put it in a gas bottle.

is a bit of an understatement.

Consider that a household LNG gas cyclinder (propane if you're central north american I guess) is typically built to contain between 100 and 200 psi whereas hydrogen requires high pressure tanks to contain between 5,000–10,000 psi.

That's a factor of 50 difference in required containment pressure capability.

Standard industrial gas bottles are 200 or 300 bar (2900 or 4350 psi for the metrically challenged). They work just fine for storing hydrogen [1].

[1] https://www.lindedirect.com/resources/gases/hydrogen

That's indeed how hydrogen is transported around today. The thing is, the volumetric density of hydrogen is quite bad. About 3x less energy than methane in gas form, which is similar to the difference in energy density in liquid form too.
And the hydrogen will still diffuse into the steel. And make it brittle so all bottles, pipelines etc have a limited lifespan compared to infrastructure for methane. And you always need pumps to get it from one containment into another because it stays gaseous all the time. Don‘t get me wrong, all these problems are technically manageable. But from the economic perspective the H2-hype is not reasonable at all. H2-application will stay niche application. Getting iron ore reduction away from coal would be a huge accomplishment given the economics of H2.
This is yet another misconception. Hydrogen embrittlement is due to atomic hydrogen being created in chemical reactions. Gaseous hydrogen consists of H2 molecules which do not lead to embrittlement [1].

[1] https://en.wikipedia.org/wiki/Hydrogen_embrittlement

You can add hydrogen to natural gas (using existing pipelines and storage), and so slowly replace that. No changes to existing infrastructure needed up to maybe 20% I think.
You can but there are concerns about hydrogen being a smaller molecule so we’d get increased leakage (with knock on effects)

No one really knows how our existing natural gas infrastructure will cope with hydrogen

Natural gas infrastructure already deals with hydrogen: 2% of natural gas is hydrogen. For town gas which was used before (made from coal), hydrogen content was around 50%, so this isn't entirely new. Of course you can't re-use the existing infrastructure and use 100% hydrogen.

This isn't black-and-white. Leakage is a disadvantage, as it is for fossil fuels (natural gas, oil, coal,...). Other technologies have other problems: windmills kill birds and bats! Pumped storage kills fish! Dams cause methane leaks! It is important to quantify how much of a problem those disadvantages really are.

hydrogen worsens the impact of methane in the atmosphere and as such simply pumping hydrogen through existing infrastructure sounds pretty dangerous.

https://theconversation.com/dont-rush-into-a-hydrogen-econom...

https://agage.mit.edu/publications/global-environmental-impa...

more skeptically, given that green hydrogen remains a pipe dream, it's both a useful delaying tactic for switching to electricity and furthering investment in fossil fuels, which must stay in the ground if we are to have any hope of staying below 1.5c.

https://www.carbonbrief.org/new-fossil-fuels-incompatible-wi...

Natural gas already contains hydrogen. Up to 20% of hydrogen in natural gas doesn't sound all that dangerous. The article you linked says "if a hydrogen economy replaced the fossil fuel-based energy system and had a leakage rate of 1%, its climate impact would be 0.6% of the fossil fuel system.". So the climate impact would be 100 times smaller(?)

Yes there are many delaying tactic for switching to electricity (the promise of "synthetic fuel" for example, to power existing gas cars). But using hydrogen to replace fossil fuels is needed anyway, for example for ammonia production and steel manufacturing. So I don't understand why you think hydrogen will delay the switch to electricity.

I mean, this doesn’t have to go into cars / be distributed widely… it could just used to time-shift solar energy to night time by burning it on-site. Which means you only need to solve the storage problem.
Which is already solved: salt caverns work well.
I checked and: "Salt caverns are artificial cavities in underground salt formations, which are created by the controlled dissolution of rock salt by injection of water during the solution mining process."

Yeah, I don't have one of those in the garage unfortunately. I do have space for one of these though https://newatlas.com/energy/lavo-home-hydrogen-battery-stora...

Hydrogen is not the storage solution for your garage. A normal battery is better suited. Hydrogen is for storing weeks worth of energy at grid scale.
I doubt even 15% efficiency would be there; along with massive maintenance/size issues. Solar is cheap and easy when it comes to maintenance, effectively no moving parts. Internal combustion (or a gas turbine) is a whole new development... and there is the storage.

The best bet are still batteries, albeit the current incarnation of LiXXX (e.g. LiFePO4) are still not there. Even storing energy in batteries poses multiple conversions of electricity that goes to 92-95% efficiency.

No, too many losses. Same problem with storage.

Use isn't that expensive, fuel cells do exist.

The problem with green hydrogen (made with electricity) is the inefficiency.

It's only good for storage when you have already filled every battery and pumped hydro storage you have and are still making an excess. Electricity -> hydrogen -> electricity conversion is so hilariously inefficient that even petrol engines can beat it.

I don’t understand that comparison. You can’t use electricity to make petrol, right?
Synthetic fuels can be created with electricity. But, again, the efficiency is laughable. The amount of energy lost in the conversion is so huge that it's not viable unless you've got crazy levels of overproduction.

But my comparison was about the fact that petrol engines convert only 20-30% of the energy in the fuel to actual motion - everything else is lost in friction and output as heat.

Toyota had a prototype engine that went up all the way to 35-37% efficiency, but it didn't make it to production.

Modern electric engines are 90-95% efficient.

Fuel cell vehicles also use electric motors. They will not lose to combustion engines on efficiency. You seem to contradict yourself on how you think hydrogen vehicles work.
Fuel cell vehicles sill need hydrogen to generate the electricity.

Hyrdogen has about 80% losses from electricity to wheels. When 55kWh of electricity is used to generate hydrogen and that is used in a Toyota Mirai to move the car, only 11kWh ends up at the wheels.

If you do that same with a Hyundai Ioniq 5, all 55kWh (minus some transfer losses) get to the wheels.

Those are purely made up numbers. A fuel cell will easily be more efficient than an internal combustion powered car. Also, a battery is not 100% efficient, nor is charging an EV 100% efficient.
No petrol engine can match a fuel cell on efficiency. Especially once you realize the existence of refining losses.
I refer you to the current documentary on Netflix called _Glass Onion_ that examines this problem.
While I really like the movie, the hydrogen technology part and its dangers are entirely fictional.
I never understand why people are so obsessed with the problems of using hydrogen for transport. We use millions of tons of it for making fertilizer and other industrial processes. We could potentially expand industrial uses to include steel and replacing methane in high heat applications.
"The catalyst is made of indium gallium nitride nanostructures, grown onto a silicon surface."

World gallium production is 400 tons a year. World indum production is 70 tons a year.

How did "cheap" get into this?

Production is driven by demand and will very likely expand now that prices are rising again, just as production doubled back between 2011-2014 when last the price/kg rose [2] as it has in recent times.

Annual Gallium usage includes a substantial amount of reclaimed material from electronics which isn't counted as production against reserve.

> World primary low-purity gallium production capacity in 2021 was estimated to be 774,000 kilograms per year; high-purity refined gallium production capacity, 325,000 kilograms per year; and secondary high-purity gallium production capacity, 273,000 kilograms per year. [1]

[1] https://pubs.usgs.gov/periodicals/mcs2022/mcs2022-gallium.pd...

[2] http://strategic-metal.com/products/gallium/gallium-price/

( Similar story with inidium )

Most rare elements are extracted primarily as side products. Scaling production directly is very difficult without demand for the co-occuring minerals.
Gallium is a side product of producing aluminum and zinc. Most processing of gallium-bearing raw materials for aluminum and zinc production does not currently incorporate any gallium separation stages. Current rates of gallium production can increase 5-fold without increasing rates of aluminum/zinc production or improving extraction techniques; current extraction techniques would just need to be deployed more widely.

See "On the current and future availability of gallium":

https://www.sciencedirect.com/science/article/abs/pii/S03014...

https://sci-hub.se/10.1016/j.resourpol.2015.11.005

Love the way you just slid right past the indium there which is the one that actually matters.
Fortunately Gallium comes primarily from either bauxite (aluminum) or zinc deposits in more or less the same amount (~50ppm).

Ergo there's 50 tonnes of gallium per million tonne of bauxite, or 5,000 tonne of gallium in the annual 102 million tonne per annum bauxite production of Australia (alone).

These 5,000 tonne exceeds the current global demand for raw pure gallium by a factor of ten .. so it's not the demand for aluminum or zinc that's limiting global gallium production.

Yes. I definitely meant the gallium alone and was not including the indium.
The wikipedia article on Indium: Production and availability [1] is ballpark okay and puts

> the supply potential of indium at a minimum of 1,300 t/yr from sulfidic zinc ores and 20 t/yr from sulfidic copper ores.

(ie potential max supply estimate as by product from mining other minerals)

This is almost double the current demand. Other industry reports are more optimistic than the source cited here in wikipedia but as a ballpark it'll do.

The wikipedia article has a decent description of one facet of the rare earth problem, that these elements are always bound up with other elements and are only economically feasible as by products.

The other great issue is the flip side of the same issue; they are bound to other elements and must be chemically seperated after mechanical pre processing .. and this can be lengthy, expensive, and leave acres of toxic waste to deal with.

[1] https://en.wikipedia.org/wiki/Indium

If HSJ couldn't push extracting this extra Indium across the line due to lack of Indium whilst being better than PERC and TOPCon PV in every other way, it seems doubtful that one photocatalytic method out of a bunch can displace a PERC cell and an alkaline electrolyser that produce about the same amount of hydrogen per m^2 without the expensive vacuum deposition step.

More methods are always good though and hopefully the barriers to commercialising this method (or one of the others) have workarounds.

The indium story is not similar.

Indium is one of the least abundant elements.

In the entire Solar System it is less abundant than gold.

In the crust of the Earth, it is less depleted than most other metals with high electronegativity (like silver and gold), so the result is that here indium has about the same abundance as silver.

Indium is completely irreplaceable in LEDs and in high-speed power transistors. The future demand for these two applications alone is severely constrained by the existing indium reserves (e.g. replacing all light bulbs and laptop/phone chargers and computer PSUs, in the entire world, with more efficient modern types would need a lot of indium).

Because of that, extreme efforts are needed to find substitutes for indium in its other applications, like for the computer displays, all of which currently use transparent electrodes made of doped indium oxide.

It is very undesirable to find new applications that would consume more of the scarce indium.

Odd comment phrasing, ChatGPT?

Sure, so in the crust it's as common as silver.

But that, the mean average, is hardly what matters- there won't be much in beach sand, but find the right copper-porphyry deposit and it's there as common as gallium ~50ppm.

It's also a prime example of why the world needs to better recycle electonic waste, indium-tin oxide (ITO) thin film displays from the tip are a better source of indium than chewing through a million tonne of Cu-porphyry.

If there had not been a few kinds of mineral deposits where the indium concentration is much higher than its average, while still being very low, indium could not have been used for anything, as its price would have been too high.

Even so, because the total amount of indium in the Earth's crust is about 200 times less than that of gallium, and they are concentrated by similar geochemical processes, it is likely that the ratio between their exploitable reserves is about the same.

In any case there is no doubt that the exploitable reserves of indium are much less than for almost all other chemical elements, the main exception being most of the so-called "precious" metals, about which everyone is aware that they are rare.

Unlike most other really rare chemical elements indium is needed in equipment present in each modern home and business, even if in minute quantities.

Because of this, indium is on the top of the list with chemical elements for which it is required to find substitutes in their current applications, otherwise in the future the supply will not satisfy the demand, and for which new applications should be avoided.

> Even so, because the total amount of indium in the Earth's crust is about 200 times less than that of gallium, and they are concentrated by similar geochemical processes, it is likely that the ratio between their exploitable reserves is about the same.

Ahh, reasoning ("likely that").

And yet, empirically, Gallium and Indium are found in similar porphyry-type mineral deposits at similar ppm concentrations .. despite being both rare and hard to find elsewhere (with indium being more or less as common as silver in the crust).

I get it - I have a strong math background and can understand your "reasoning" from the concentrations .. but then I spent a decade or so in exploration geophysics and then did the back end of a fairly authoritive global scale mineral resource database which changed my outlook on things somewhat.

I also have a shovel handling bob cat driving view of what it's like to mine in excess of 800 million tonnes of reserve depoit per annum and a production engineer level overview of various post processing circuits to extract concentrates for further processing.

You do realize that the substrate is made out of silicon and that the thickness of the indium gallium nitride layer is only a few micrometers?
If you're looking at square kilometers of something made of indium you need to be talking nanometers not microns. Hence why it's just barely not a critical mineral for PV and why CIGS was a non-starter.
Is it just me or has it been like 18 months of one supposedly "game changing" hydrogen catalyst after another? I'm not trying to be cynical. It just seems the science press is awash in results from one research project after another in this area and I find it very difficult to rank which ones have any credible chance of utility.
I'm also sick of 18 months worth of negative comments about how hydrogen is a waste of time...
The truth is that we can already produce hydrogen at like 80% efficiency with PEM electrolysis. There is not much "game changing" left, except for improving cost.
I am waiting for the day when there is an affordable (<$5k? <$10k as an absolute maximum) residential system that can run on home solar and produce ethanol/hydrogen/ammonia/whatever combustible fuel from excess electricity. Round trip efficiency can be horrible, so long as the system is low maintenance and can be configured to run exclusively off of spare generation.

Is anything like that on the horizon? Or do all of these liquid fuel synthesis options require industrial pressures/volumes/input electricity so as to forever be out of reach from residential synthesis?

> combustible fuel from excess electricity. Round trip efficiency can be horrible

If that's really all you want, you can get a 9 year old to put together some kitchen waste and art supplies to achieve this.

That's how I did it at that age.

I did use a battery though, so you might want to check the wiring and add a voltage divider, but those are also easy to build even without understanding.

And I have no idea if you even can, let alone should, just pour gaseous hydrogen into, for example, a gas heater's fuel input pipe.

But actually making hydrogen is utterly trivial.

Low maintenance, safe, compact, and high enough output is a different story.

For the second, you probably want a methanol, methane or ammonia output and they all require high temperatures or exotic materials.

In my opinion you are mistaken , affordability does not mean home appliance.

Hydro is pretty cheap , does not mean it’s fit for home.

Here the best scenario is similar to Singapore - Australia or UK - Morocco remote solar grid.

This innovation is very interesting compared to Water- Hydrogene electrolysis that is a bit expensive and needs metals that are going to become difficult to source in the coming decades.

Gallium is quiet abundant from my understanding.

This is currently the Lavo hydrogen electrolysis product for home use [1]

However the storage tanks are quite small. I would prefer if they made the hydrogen production and storage separate, so you could save up hydrogen in the summer to use in the winter.

[1] https://www.lavo.com.au/

Hydrogen storage is not something that you really want to do at home, especially in "saving up" quantities. It is quite happy to explode, you need tremendous pressures and low temperatures for efficient storage, and also hard to contain (many "normal" materials are permeable to hydrogen). [1]

[1] https://en.wikipedia.org/wiki/Hydrogen_safety

There are ways of storing hydrogen in metal hydrides at room temperature and pressure. This makes a LOT of sense for people who may want to have an option of buying stored energy - such as those who live in apartments without access to the terraces where solar panels can be deployed.

If these metal hydride storage is used similar to how changeable batteries are used, it is conceivable that you could drive up to a place like a fuel station just to change out your metal hydride storage in a matter of a couple of minutes and perhaps even get additional supplementary units packed at the back of the vehicle if they intend to go on a long journey.

https://www.frontiersin.org/articles/10.3389/fenrg.2021.6161...

There has also been recent advances in using Boron Nitride for storage - a perfectly safe chemical.

https://www.geelongmanufacturingcouncil.com.au/2022/07/innov...

There is a case for portable storage, sure.

Hydrogen at scale is going to look more like a means to export sunlight energy from equatorial climes (Australia, Sahel, etc) to Europe, the northern US, Canada as required.

Efficiencies dictate the most likely roll out is large central generation of electricity and dispersal via the existing electrical grid system.

In a similar view individual per apartment solar panels make little sense, panels should be built into entire buildings .. across roofs and across any required parking structures, etc.

Is the watts/kg for this electicity ->hydrogen+metal hydride storage solution better than an electicity -> lithium-ion battery solution ?
> Hydrogen storage is not something that you really want to do at home, especially in "saving up" quantities. It is quite happy to explode, you need tremendous pressures and low temperatures for efficient storage, and also hard to contain ..

Agree, hydrogen storage is not something you do as easily as say piling up some fire wood.

On the other hand, it's totally possible to do at home and it is being done. Hydrogen can be stored in regular gas cylinders. See the realized projects from Home Power Solutions [1].

If these cylinders are located outside, explosions should be rather unlikely due to ventilation.

[1] https://www.homepowersolutions.de/en/picea-plus/

10k is an absolutely wishful thinking - 10k is just the low end of a bog standard geothermal pump.

Also what's the purpose of the ethanol (the rest are not useful, esp. hydrogen which has to be stored somewhere, ammonia is rather dangerous)? I can imagine making vodka alike - but beyond that, using internal combustion engine to burn it means an extremely very low efficiency to conserve enegy. The energy density is there but the efficiency is not.

Heh. Yeah, I was thinking that any kind of home synthesis operation was unlikely to offer a financial payback. Hence the low aspirational cost, but you are right that figure is laughably low.

Ethanol - easier to synthesize than gasoline (which is a complicated mixture of hydrocarbons). It has ~2/3 energy density of gasoline, which I do not think is horrible. I believe it is also less volatile and easier to store long-term.

Couldn't it just burn off excess hydrogen? It would just be H20 byproduct.
If you do and you're my neighbor please wait with switching it on until I can move away.
You can effectively accomplish the same thing from an environmental perspective by running your house as efficiently as possible. If you already have home solar, you are reducing the amount of carbon put into the air by power plants. Since CO2 molecules are indistinguishable from each other, that carbon reduction could just as well have come from burning renewable synthetic fuel made at home. If you have a big solar setup and sell excess back to the grid, that carbon reduction will be larger than if you used the same energy to inefficiently synthesize fuel.
You can't operate a car / tractor / hot air balloon with just an efficient house.

Also, you can't run your house on an efficient house + solar over the 2-6 months the sun isn't in the right place (in the sky) for very long or when your panels are covered in snow for a week.

An efficient house gets you to the table and is a multiplier, but long term energy storage is also really important for lots of people.

Hydrogen, though, that stuff's tough. I think 99% of Hydrogen advocates don't understand just how nasty the stuff is.

Interestingly, our solar panels seem to shed the snow pretty fast, in fact faster than the plain roof. I guess the black cells warm up in the sunlight and the snow just slides off them after a couple of days. Pre-solar, we used to have to rake the roof to prevent ice dams from building up, but no longer.
It's probably more efficient to centralize storing weeks worth of energy.
Perhaps. But then that means the power lines need to be maintained, even when not in use. I'm not sure what the amount is, but it's probably not insignificant.
I live in New Mexico with a 6.7kW array. My house is heated with air source heat pumps. In the summer, we generate 3x the electricity we need. In the winter, we generate 1/3x of the electricity we need. Last year we generated 91% of all our electricity, the year before 93%.

We would need a gigantic store for heating our house, because for 4-5 months a year, we are generating less electricity than we need. Something on the order of 15MW of storage.

We could certainly our home's thermal efficiency, though this would be complex. We could also add more panels, but then we'd be overproducing by even more during the summer.

15MWh of storage seems very high? I appreciate I don't know your raw numbers of production and consumption, but don't you still produce some power during the winter? ie; you would only need to cover your shortfall.

For context, I live in the cloudy-ish south of Australia, and have similar problems with our solar power in winter. However, we still produce reasonable amounts of power through the day, and our total winter shortfall is only about 500 kwh, once offset against the daily production.

So for us, 500kwh -> 2080.8 MJ -> 462.4 litres of storage required (assuming 4.5 MJ / litre and ignoring round trip losses), which seems an entirely reasonable for local storage, safety aspects not withstanding.

Our problem is not the shortfall in the winter generative capacity (sure, it drops a bit, but is still not far from 1MW/month). The problem is the increased load required for heating. I figure we need about 3MW/month for heat, for maybe 4-5 months, but you're right, the storage would only need to be 8-10MW, not 15MW since we'd still generate about 1MW anyway.
That depends on how far away the center is and whether you trust the people between here and there.
Part of my thinking was for fully off-grid homes. Are we approaching a point where they could capture the excess for long-term storage? Batteries are not the answer.
Many people in rural New England have or wish they had secondary power generation because you need that local energy more often when there are external events that likely also break the grid (big snow storm).

The chain of events is "once in a gazillion century storm wipes power to huge region; millions of households are stuck without power, power company can't go out and fix all the broken things for weeks/months, many people have their houses wrecked by frozen pipes / die from running poorly improvised heat systems"

The round trip energy storage with batteries is pretty good but not terribly cheap at scale. The round trip into hydrogen, theoretically, seems pretty good but the actual "nuance" in the equation is basically a bunch of dragons waiting to eat you and everyone who ever loved you. Anyone selling a "power into hydrogen" thing is probably actually selling a "turn natural gas into hydrogen and sell that hydrogen to hippies" thing.

Maybe if you can figure out how to stick a carbon or two or three onto those hydrogens you'd be in business, but it's hard to get those carbons.

Anyhow, this is a hard problem. People have gotten used to hydrocarbons which are basically magic given their stability and energy density.

If the concern is gaurenteeing that power is always available, the answer is a backup generator. It won't consume fossil fuels unless it's actively in use (very rarely). The carbon taken out of the atmosphere by having an efficient house with solar and grid connection during the rest of the year will more than offset the generator.

I contend that the unsexy combination of solar, a bidirectional grid connection, and an emergency diesel generator is more efficient and environmentally friendly than any existing system involving hydrogen or batteries.

Hydrogen storage is not particularly cheap either. I would be surprised if a house-scale system can beat batteries in terms of cost.
> Maybe if you can figure out how to stick a carbon or two or three onto those hydrogens you'd be in business, but it's hard to get those carbons.

Or maybe you stick three hydrogen atoms to one nitrogen atom and have ammonia.

It's pretty obvious that the single most important reason why the vast majority of machines/engines runs on hydro _carbons_ instead of hydro nitrogens, is that hydrocarbons have been humanity's most important energy source for centuries.

So it makes sense, everything is geared towards them.

But for the future, ammonia appears to be a much better choice, because nitrogen is readily available and the only thing that's missing is matured tech that runs on ammonia. Fuel cells, engines, ...

IIRC there are already container ships being built that run on ammonia.

This is all correct with the caveat around how you want your "features" to be defined and how you want your "bugs" to be defined. Most notably, that's around the grid.

Implicit in your assumption is that the grid is reliable, always on, not subject to geopolitical or climate risks, etc. "Inefficiently" converting solar power into otherwise portable fuel might be a feature rather than a bug for those living in conditions where the central grid is often unreliable. Before the past few years, I'd say that would generally be countries in the global south, but we've seen a lot more grid instability even in the US as of late.

I think the closest to what you need would be some sort of pico hydro with pumped storage.
Why not just a 20kWh battery for energy time shifting. Or are you looking to sell the hydrogen?
This will last less than a day.

What to do in the winter? If the answer is "use the grid", then we just kick the can to someone else, who will probably use fossil fuels to provide the energy. The basic problem remains - solar/wind are intermittent and fluctuating.

Compressed air has a higher round trip efficiency than storage, and pumped hydro is twice as efficient as compressed air.

However until zero kWh is generated from fossil fuels in summer, solar/wind and battery is a massive gain, even if gas is still used for 2 months a year.

But gas is used also in the summer. And energy is not only electricity - heating is currently done mostly by natural gas, and is often absent from those calculations.

Efficiency is irrelevant. The only thing that matter is cost and feasibility. The cost of energy from solar is ~$0.02/kwh and sometimes even $0.00/kwh (when the grid curtails production). Even with 30% efficiency each kwh retrieved from storage will cost a record-low of $0.06/kwh (3-10 times lower than the consumer price).

The biggest factor here is the capex and ease-of-use of the equipment. Not the energy input cost.

The commenter's goal is presumably season-shifting, which is two orders of magnitude off from feasible battery capacity. In most areas in the US, a full-roof solar system will produce enough energy in aggregate to power the home's use year-round, but there's no way to get all those summertime watt-hours into the lines in winter when the panels are dark.

But indeed, no, this just doesn't work. Best available efficiency for round-trip electrolytic fuel production / electricity generation is 40% or so, meaning that those roof panels wouldn't be enough anyway. (Also there's the problem of having every home store a winter's worth of pressurized hydrogen or whatever on-premises. Yikes.) It's not worth it.

Home solar is attractive because unlike most infrastructure it scales down really well and is actually feasible to do at the level of an individual user. But, like most infrastructure, seasonal power management is a grid-wide problem and needs to be solved at the utility level. There are plenty of tricks available there that homeowners don't have access to.

No interest in storing a season's worth of energy which would be infeasible without a ludicrously over provisioned system. More -what could you do with spare capacity that is not trash-tier net metering? Generating liters of fuel weekly would be enough to power my ICE car (I rarely drive). Or being able to generate and store a ~week of liquid backup energy.

Such a system would be unlikely to ever payback for itself. Not deluding myself on that one.

Depending on where you live, simply electrifying your home and driving an EV should be enough to get you within a few percent of your peak summer output. You won't be wasting that much. Buy the heat pump water heater, the induction range, etc... Pick the low hanging fruit, then worry about using that last bit of juice in June.

FWIW: net metering seems like "trash tier" precisely because that summer PV excess really is mostly wasted (this is true for big panel farms too). The utilities were taking a huge haircut on the old 1:1 billing that California just rolled back. It wasn't sustainable.

If you drive say 300 miles a week that’s 100kWh for a typical electric car. Another 150 for domestic use and that’s 35kwh a day. You have a system that generates more than that if you have excess to pump into liquid storage, but why do you want a weeks worth of backup energy? Why not 3 days? Or 2 weeks?
A composter costs very little and can product a decent amount of methane.

Animals like goats and pigs can produce a lot of dung that will turbocharge that quite a bit.

A little searching yields stuff like: https://www.motherearthnews.com/sustainable-living/renewable...

The low tech route is far cheaper and easier at small scale if you want to make combustible fuel.

It’s just a matter of cost. Cost savings will come from improved efficiency and manufacturing innovation. You can make a lot of electrofuels in a distributed way:

Hydrogen (Water + Electricity): There are many containerized electrolysers

Ammonia (Air + Electricity): https://www.nitricity.co/

Methane (Air + Electricity): https://terraformindustries.com/

Unless you need hydrogen for a capability that only hydrogen has it is much more efficient to use solar electricity either directly or to charge batteries.
In those parts of the globe where it makes sense to use solar, and during the day, yes.

For everything else, you need a way to store the energy that can be measured in weeks, not hours. You also need to transport it. And you need to stabilize the energy output not to be entirely dependent on whether the sun shines. That's why hydrogen might be a good energy reservoir.

> a way to store the energy that can be measured in weeks,

My Tesla Model S does that pretty efficiently. And for static batteries there are plenty of alternatives that don't use difficult to source elements.

> You also need to transport it.

We have a grid to do that already, with HVDC interconnects we can even sell it to places where the sun is not shining.

Yes hydrogen is has a pretty terrible volumetric energy density. In gas form stored at 200 bar, you'd need about 18 truckloads to math the amount of fuel in a single truck load of petrol. In liquid form stored at a few degrees above zero it gets a bit better. It's "only" 2.5 times less dense than lng. Of course cooling and keeping the gas at that temperature is not free. It takes energy. And as it heats up, you have to boil some of it off. So, it doesn't store that well for longer time in liquid form.

So, that makes shipping or trucking around hydrogen spectacularly uneconomical. Most hydrogen produced today is used onsite. Mainly for things like fertilizer production. Moving hydrogen around at scale is an unsolved problem. Gas pipes (after they are re-enforced) could work of course. But some of it would leak. And hydrogen mixed with air is not a good thing to have in your house.

The same property also makes using hydrogen as a fuel in planes or shipping unpractical: most of your plane/ship would be taken up by the enormous volume of hydrogen you'd need to move it around.

Michael Liebreich's hydrogen ladder is a good reference here. https://www.linkedin.com/pulse/clean-hydrogen-ladder-v40-mic...

In it he organizes different use cases by their economical value. Things like road transport and domestic heating are at the bottom of the scale (i.e. you could do it but it would be very inefficient and costly). Near the top are some of the more realistic things, some of which are already being done.

Instead of moving hydrogen to where you implement those use cases (e.g. steel making), it would be more practical/logical to move the use case to where you can produce the hydrogen the cheapest. The bigger the energy need, the higher the savings. You basically compete on energy cost.

The bet seems to on the cost/tradeoffs of producing batteries vs producing hydrogen generators. If at some point producing hydrogen generators can become more affordable and sustainable than batteries (especially from countries will low rare earth resources) it would be a win for them.
Impressive idea. Hope they get a better efficiency factor.

On a side node, you can already add Hydrogen to your home. There is a startup in Berlin, DE which sells complete systems for home: solar roof, heat pump, electrolysis device, bottles and ventilation system.

During summer you fill the bottles with H2 and during winter you consume it.

I'm not affiliated with them. The price before Corona for the whole system was around 65k Euro and now around 100k Euro.

https://www.homepowersolutions.de/en/product/ Picea is the name

Nice! So it seems demand is so high they can increase their prices.

Do you know what the capacity of a single system is? Could one unit be shared between multiple residential units?

If I understand correctly, this is producing hydrogen and oxygen mixed together. This is useless. It's also overall less efficient that commercial PV cells driving commercial electrolysers.

One common issue with all these concepts doing electrolysis at the collector is how do you gather the hydrogen. Rigging PV modules together with wires is much more practical than hooking hydrogen emitters together with tubing or pipes.

Cheap and sustainable in your lab, neither once it hits the market.
Would we use these like regular existing solar panels on our rooftops? And does 10x efficiency mean that we could harvest 10x the power of what existing solar panels provide?
I do wonder about the potential of converting excess summer-time rooftop solar energy into storable liquid fuels of some sort (e.g. methanol) for winter-time heating.
I am doubtful that this scales. Main concern is the cost in materials, fuel, and electricity in manufacturing large lenses. Sure, it seems that there are large increases in efficiency when generating hydrogen.. But not really once you take into account the cost of generating the infrared.