Solar-driven water splitting at 13.8% solar-to-hydrogen efficiency
pubs.acs.org
pubs.acs.org
Tesla is switching from lithium-ion to lithium iron phosphate for fixed battery installations.[1] The energy per unit weight is somewhat lower, but that doesn't matter much for fixed installations. The safety is better, too - lithium iron phosphate batteries don't have the thermal runaway problem. BYD, which is the biggest producer of batteries in the world, sells shipping container sized lithium iron phosphate sized battery packs for large scale solar backup.
[1] https://www.utilitydive.com/news/tesla-shifts-battery-chemis...
The typical solar panel is maybe 25% efficient or less. The typical steam engine is maybe 50% efficient. Once things are in the form of electricity, we have a large variety of options for efficient transport and storage.
But sometimes electricity isn't useful. Li-Ion will never be light enough for a serious airplane for example, while hydrogen _IS_ light enough for an airplane. (But maybe too volumetric, as every practical H2 airplane engine relies upon high-pressure storage or even cryogenics to keep H2 at a small enough volume).
EDIT: If we think of it as chemistry... perhaps we can make liquid fuels out of H2 like coal liquefaction turns one fuel source into another. After all, classical fuels are nothing more than carbon + hydrogen + energy... and H2 is a very efficient form of storing energy for that reaction. Or maybe we learn to just use H2 directly? There are fuel cells and engines running on H2 today, but I'm always worried about the volume of H2 (requiring either compression or cyrogenics before you reach practicality).
Hydrogen: See Hindenburg.
I would rather not fly in a bomb. I just don't see it being viable for planes.
We're starting to see short distance small planes electrify and then long haul will probably go synthetic fuels over the next 10 years.
I agree though, planes and H2 probably don’t mix. Jet fuel should not be a priority to replace with H2. Priority should be given to static applications before trying to apply it to moving vehicles.
The main concern for hydrogen as a fuel now is the high pressures. If the pressure vessel is damaged it explodes due to mechanical forces. This is not impossible to work around. Consider, for example, that gas tanks can already be punctured and lead to fires; it takes a fair accounting of the risks to really rule out hydrogen as a fuel.
There are still dangers, but practically I'm not sure they are that much worse than a gasoline fire. There are also systems that reduce the pressures needed, like activated carbon beds. Research on them stalled mostly because there was no good way to generate H2.
You rarely by accident get a stoichiometric mix. With a slow leak into an enclosed container is usually how it happens. Otherwise there is too much fuel to O2 in the atmosphere.
People really need to stop trying to sound smart by thinking of imagined dangers. That is what stopped nuclear power, it's what's stopping hydrogen as a fuel, it's what's stopping gene therapy research, etc. Get over yourself.
> Get over yourself.
Right back atcha.
Good grief, "stoichiometric mixture" is not a reasonable person's danger threshold. The mechanical energy alone is terrifying, which was the point of bringing up COPVs.
While we're at it, let's put giant flywheels in chemical cars to do regenerative breaking. They'll probably have less mechanical energy than the titanic so they're probably no big deal, right? Right.
I'm doing as best I can. I happened to have a coworker who was involved in alternative fuels research, specifically the H2 cylinders that operated at lower pressures using a carbon substrate. But even if you don't use that you can still construct and secure the container so it splits instead of shatters and contains most or all of the debris. You can install a shield bulkhead into the car to deflect debris to the ground. You can do loads of things.
You are not original, you are not the first person to raise these concerns, and very competent people have been working on them.
They tested the incendiary paint hypothesis on the TV show Mythbusters.
The MythBusters concluded that the paint may have contributed to the disaster, but that it was not the sole reason for such rapid combustion.
As opposed to the kerosene fueled bombs we're flying in right now?
I'm not sure comparing things to close-to-wartime tech from 90 years ago is a valid approach.
You might be surprised how good WW2-era scientists were at chemistry and science.
The earlier poster has a point. Gasoline, Diesel, and Kerosene have all been studied extensively (especially in the 1930s and 1940s BECAUSE of preparations for WW2). The safety of soldiers was paramount even to the Nazis.
War machines: be they airplanes, tanks, or battleships, were all going to be exposed to enemy fire and explosions. These fuels (Kerosene and Diesel in particular) were chosen because they're extremely safe: high flash points and even higher auto-ignition points.
That means that kerosene __literally__ can't catch on fire at room temperature. You need to warm up kerosene before its appropriate to burn (Of course, once its burning it will warm up the rest of the kerosene and keep burning. But this isn't some super-explosive volatile chemical we're talking about here)
Gasoline is still safe, but not as safe as the other two (-40C Flash Point). Gasoline was safer than a lot of the other petroleum products that were investigated back then, and was still chosen as a fuel for war machines.
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The same is not necessarily true for H2. H2 will explode at any temperature (even near absolute zero).
I'm well aware of chemical prowess in that period, especially on the German part. They had a bunch of Nobel prize winners.
However, that's why I said "close-to-wartime". First of all, in case you weren't aware, the Hindenburg was supposed to use helium but due to a lack of helium in Germany (I think it was primarily due to American export restrictions), they had to use hydrogen.
I don't know of other limitations for the Hindenburg, per se, but knowing the overall German shortages of the period, I wouldn't be surprised if they had other structural issues with the Hindenburg itself, especially since it wasn't designed to be used with hydrogen.
On top of this, the Hindenburg design was from the late 20s, 1929, I believe.
If materials science, modeling, etc haven't advanced since 1929, I'll eat a shoe. If we're somehow worse at managing hydrogen after almost 100 years, I'll eat the other shoe.
The Hindenburg crew had to regularly test the hydrogen cells for oxygen content.
I wouldn't say paramount: https://en.wikipedia.org/wiki/Messerschmitt_Me_163_Komet
(the Komet had a tendency to blow itself and its pilots up due to the hypergolic fuel)
I'm not sure those were really the reasons for the choices that were made in most cases. Airplanes of the era used gasoline engines because Otto engines provided much better power/weight than the diesel engines of that time. For submarines, I'm not sure safety was a bigger factor than being able to use the same(?) fuel oil that the predominantly steam powered surface fleets were using, and that diesel engines provided better fuel economy than gasoline ones.
One place where safety might(?) have been a factor was that the USSR decided to power its tanks with diesel, whereas the other major combatants used gasoline engines in their tanks. I'm sure this prevented a lot of fiery demises for Soviet tank crews.
EDIT: That's what its called. H2 is a component of Syngas (https://en.wikipedia.org/wiki/Syngas). Syngas can then be further processed into kerosene, gasoline, or other fuels we use.
You're describing hydrocarbons.
The most-common element in the universe married to the most-common four-bonding element. Using solar panels to synthesize Jet A is probably a better path forward than redesigning every plane in the world to trawl a balloon or carry a pressure vessel.
There's a reason pretty much all of Earth's biology uses hydrocarbons as its fuel of choice.
Why would this be desirable?
/s, mostly
Well yes. But I'm also aware that H2 is a component in the synthetic production of those hydrocarbons. Using the H2 directly could prove beneficial. But if not, then we can always convert it into some combination of C and H and burn that instead.
Either way: producing H2 from clean sources (like this weird chemical solar panel thingy) is a good thing.
Adding hydrogen can fix both of these problems, enabling efficiency up to 150% (compared to the energy in the source material, not including the hydrogen). This is kind of a big deal, since for large-scale carbon-neutral production of synthetic hydrocarbons the bottleneck is the source of carbon. Hydrogen can be produced (nearly) carbon-free in unlimited quantities, but barring a breakthrough in DAC technology where is your sustainable source of carbon? And no, we don't want to replace pristine rain forests with biomass plantations.
Silanes as Fuel for Aerospace Propulsion
https://ui.adsabs.harvard.edu/abs/2009TrSpT...7.Pa33S/abstra...
If this is a useful way to get H2 feedstock for producing ammonia, that’s interesting on its own!
Exposure to high concentrations of ammonia in air causes immediate burning of the eyes, nose, throat and respiratory tract and can result in blindness, lung damage or death. Inhalation of lower concentrations can cause coughing, and nose and throat irritation.
The benefit of nitrogen fuels as a carbon-neutral fuel is that getting nitrogen from the atmosphere is a lot easier than extracting carbon dioxide from the atmosphere.
I feel you are suggesting the reason is because it's an ideal energy transport mechanism, while ignoring the (not insignificant) fact that almost all the hydrocarbons we've used so far have been, effectively, free energy.
Or at the least, incur a cost that we have not yet had to contend with.
The reference to biology using hydrocarbons as its preferred energy store is one to fat, not fossil fuels.
That’s far from free energy. And life likely wound up that way because its precursors—hydrogen and carbon—are readily available, it’s energy dense both volumetrically and by mass, it’s safe and it can be converted into various forms of energy directly and easily.
Ultimately, the big unknown is the cost of synthesising Jet A. I think it will be low enough that it blows the hydrogen hypothesis out of the water, but I don’t have more than a hunch to go off.
Yes. Most of the available energy is in the hydrogen bonds, but if you want to 'tame' neat hydrogen by binding it to something else, from all the stuff in the periodic table carbon is pretty much the optimal choice.
> Ultimately, the big unknown is the cost of synthesising Jet A. I think it will be low enough that it blows the hydrogen hypothesis out of the water, but I don’t have more than a hunch to go off.
To the extent one of the inputs to synthetic Jet A is hydrogen, it won't be cheaper as such. So the question really is whether the added cost is low enough that the easier logistics of a room-temperature liquid fuel makes the total cost lower. I'm slightly hopeful that this will eventually be the case.
Carbohydrate != hydrocarbon.
> You're describing hydrocarbons.
This is technically correct, but at the right pressure, it becomes politically incorrect.
Right now there is already a huge push against fossil fuels, to the point that countries are setting dates for forbidding internal combustion engines in cars. Note that this will take effect independently of the source of fuel, fossil or otherwise. And methane, which is relatively easy to produce from bio-waste, it is a potent greenhouse gas.
For now, the public is divided. Nobody likes the consequences of global warming but nobody likes to give up the convenience of hydrocarbons.
Give it some time or add some more climate shock, and the public may change opinion to be against all fuels that contain some form of carbon, no matter the origin.
Nobody wants to give up the convenience of personal transportation using automobiles. And for the United States, a good chunk of which was designed around that this is a serious problem.
Technically it is quite possible to produce hydrocarbons today. In theory a government could mandate, for example, 25% green hydrocarbons in fuel in 2030.
In practice, nobody will do that because that is political suicide.
The good thing about the current BEV cars is that over the lifetime of the car they are cost effective. I will be disruptive for a while. But we now have enough experience with BEV cars to know that they are a practical solution.
Telling people that they can keep driving ICE cars in the future, without telling them that green hydrocarbons are going to cost a fortune and would prevent everybody except some rich people from actually driving ICE cars does not help.
Of course, that could all change if we can find a cheap way to make green hydrogen at scale. With current technology we need to get rid of ICE cars. We can always revisit that if green hydrogen becomes abundant.
Personally I would also be happy if all burning of hydrocarbons gets removed from cities. There is no reason to keep breathing exhaust gasses other than that the fuel is cheap.
Aeroplanes have no viable alternative right now, and the noise/particulates issue aren't as big of a problem unless you live near an airport.
Not everybody agrees with that. https://en.wikipedia.org/wiki/Electric_aircraft#Commercial_p... says over a hundred electric designs are in development.
I think some of them can be called serious airplanes.
The site doesn’t give much more info that that, so I don’t think they’re further than the drawing board, though.
I considered this might be a scam or a “give us money and we’ll see whether this really can be done”, but being a startup with Delft roots (https://en.wikipedia.org/wiki/TU_Delft_Faculty_of_Aerospace_...) gives them some credibility, I think.
I'm not as pro-Hydrogen as you but I see some potential benefits for sure :-)
A concern I'd have with this water splitting is getting the water in and the hydrogen out (and separated from the oxygen). Wires are easier than pipes.
Doing this with ordinary PV also means the hydrogen production can be dispatchable. When PV output is tight, just stop making hydrogen and use the electrical power directly.
All the little tubing collecting the hydrogen stream trickling out of these things seems like it would be a nightmare to create and maintain.
Simpler just to avoid all that and generate the hydrogen at large separate electrolyzers at the side of the utility-scale solar field (say), and then inject into the pipeline.
Really, electricity distribution is a solved problem, and has been for more than a century. And here you are arguing that something that is in very minor use at the moment is 'easier', in spite of many challenges still be to solved before it can operate at scale. I'll just leave this link here and I would very much appreciate it if you stopped making all these assertions without qualification as though possess some kind of oracle because it is bordering on the ridiculous.
https://www.energy.gov/eere/fuelcells/hydrogen-pipelines
Your whole comment history is nothing but an endless stream of assertions without evidence including ones that are 'not even wrong'. That's not the level that I expect for this site and you are not doing us a service with this. I also do not understand why the only subject you are interested in is pushing the Hydrogen angle for more than it is worth.
FYI, coal gas is about 50% hydrogen and is two centuries old: https://en.wikipedia.org/wiki/Coal_gas#Composition
We can make methane, which is a lot easier to store than hydrogen.
If you do the watt-hours per kilogram calculation the very best lithium ion batteries are something like 255Wh/kg right now.
Hydrogen fuel cell systems for small to medium sized UAS are somewhere in the 700-800Wh/kg range right now, including the weight of the (rather heavy, seriously engineered) ultra high pressure carbon fiber wrapped tanks needed for it, piping, and fuel cell.
Something like a tank of Jet-A fuel is >4000Wh/kg.
Hydrogen itself is light, the tankage systems needed to reliably contain a large volume of it on an aircraft are not.
[0] Considering the Carnot efficiency of a jet engine at ~30%, a combination of fuel cell (~60%), motor (~95%) and propeller (~80%) will still beat it by a factor of 1.5.
Batteries are great for storing electricity efficiently as you say, but that only matters when electricity is marginally expensive (sourced from fossil fuels for example). However, if you have a cheap enough marginal cost of electricity, hydrogen is a better option because of the much cheaper fixed cost of hydrogen storage per kWH.
A good way to see this: what option would you choose for storage if electricity on demand was free but only during certain parts of the day? A hydrogen tank or batteries? A hydrogen tank is cheaper. And clean energy is essentially free besides the fixed cost of the windmill/solar panel.
Yes, but this is changing and there are a number of very interesting options.
EDIT: These batteries seem to be even less energy dense than Li-ion which is one of the weaknesses of batteries in comparison to hydrogen.
In some cases not even that. Modern Lithium-ion batteries are quite good, but self-discharge still is 2-3%/month. So, if you want to store for months (say charging a battery using the summer sun to heat a house in winter), you easily lose 10% to self-discharge, in addition to what you lose between charging and discharging.
https://en.wikipedia.org/wiki/Self-discharge#Typical_self-di... says NiMH batteries even lose 30% per month.
70-85% retained after a year is a lot better. Charge in the same charger. I used to use regular NiMH infrequently, the worst way to use them. Low sd way better for that application. Also NiMH doesn't lose capacity delivering high currents like AA alkaline does.
> The trimetallic NiFeMo electrocatalyst takes the shape of nanometer-sized flakes anchored to a fully carbon-based current collector comprising a nitrogen-doped carbon nanotube network, which in turn is grown on a carbon fiber paper support. This catalyst electrode contains solely Earth-abundant materials, and the carbon fiber support renders it effective despite a low metal content.
I don't know anything about chemistry so I'll have to take their word on the fact that the elements they use are abundant.
The two concerns for area are:
1) The cost of panels to cover the area
2) The cost of the area itself, and the availability of a ton of empty space in a convenient location
If they are using abundant materials, the first is not as much of a concern, compared to photovoltaics. Since they are producing some sort of fuel rather than directly producing electricity, transmission efficiency is not really a concern*. So maybe we could plop a bunch of these things down in some sunny middle-of-nowhere desert.
* I guess is we consider vehicles to transport fuel, which must themselves burn fuel, to in some sort of abstract sense be part of the transmission efficiency, this computation could be pretty complicated.
Carbon, Nitrogen, and Iron are cheap and easy (you’re likely within body length of a large quantity right now). 32% of the earths mass is estimated to be Iron. $1/lb or less in massive quantities.
Nickel and Molybdenum are slightly harder to find, but not by much - nickel makes up 1.8% of the earth by mass and is a reasonably common metal in everyday manufacturing. It’s currently at $3.97/lb spot price at tonne quantities. Moly is in everything from greases to steels, and while typically not used in large bulk quantities alone, is available for such [https://tradingeconomics.com/commodity/molybden] at looks like $23/lb give or take.
So all commonly available elements, albeit (nanotubes) not necessarily in the form desired just yet.
You either put it really far away (increasing transmission losses and right of way issues for the much longer lines), or you put it closer and then have to deal with expensive land or difficult environmental reviews.
It is not AS BIG of an issue as it could be - for instance 30% efficient cells vs 23% efficient cells, the lower efficiency’s cost vs space usually favors the lower efficiency, but it’s still very strong overall.
Racking and wiring is one of the dominant costs in any solar installation, and a big flat desert is cheaper both to install and maintain than almost every other option by a pretty hefty margin.
Maybe the solar cost efficiency taken alone is reduced, but the system efficiency of the real estate use goes up as does the ownership value for the property owner.
Plants generally max out the amount of solar radiation they can absorb early in the day, so are not handicapped at all by partial shade. In fact, most benefit from it in numerous ways.
Installed between rows in active farmland, solar reduces water demand by up to 50%, which is a really huge benefit. Reducing heat and evaporation stress improves crop yields. So, a farm could move from barely getting by to solidly profitable by installing solar, even before selling the power. The panels just need to be placed so as not to interfere with driving a tractor between them.
So, no, there is absolutely no shortage of land for solar installations.
Relatedly, LFP are just rugged as heck batteries. They tend to have double or more the life-cycle count. 5000 cycle count before getting down to 80% capacity? In many cases yes. That's pretty impressive, and a great boon to overall lifecycle/long-term costs. Even if you're getting less energy-density, or even less energy-store/$, that battery is going to live at least 2x the effective lifespan (barring accidents, major defects, &c).
In general, anything built for high current tends but lower energy density tends to have much more ruggedness. Sanyo’s UR18650E is Li(NiMnCo)O2, for example, but in one paper shows 4X the lifecycle count of the extremely well regarded O.G. of LFP, the A123 ANR26650M1-A[1]. Even though it's considered a "lithium ion". And uses some of the rarer/more expensive materials. (Edit: re-reading the paper more closely, I'm less willing to embrace this conclusion. The A123 remains around 2000 cycle count regardless of depth of discharge pattern, while the li-ion drops to 1000 around 50% DoD.)
Not that phosphorous (The P in LFP) is projected to remain cheap/available forever. 2 days ago, talking more about phosphor's availability specifically with regard to agriculture (and rather alarmistly), "Phosphorus is essential to life and the world is running out of it"[2].
[1] http://www.jocet.org/vol7/511-C0056.pdf
[2] https://medium.com/climate-conscious/peak-phosphorus-may-be-... https://news.ycombinator.com/item?id=29244529 (2 days ago, 2 comments)
apologies. i know discussing meta-topics is against the rules. i just really dont understand why there's an ongoing basis against this content becoming popular. it's so weird to me. i want to believe there's genuine real authentic behavior behind the votes happening here & elsewhere, but it feels so so weird to see this kind of straightforward telling constantly bounded, rising, then flattened back down, again and again. it instills a larger sense of disbelief, feels like there are vulgar reactionary forces about, which is not at all a conspiracy mindset i want to fall into.
In that scenario, total levelized cost is the more important criterion that efficiency -- if these things convert solar energy less efficiently, but the contraption is cheaper than solar panels plus conventional electrolyzers because it's simpler or uses cheaper materials or whatever, it might still be the more economical bet.
This is PV powered production of hydrogen. Yes, the PV electricity could go directly to a battery, granted. But the PV cell is only about 20% efficient in that conversion. (Lab results are up to 30%.)
There are use cases where rather than an electrical transmission line needing to span an ocean, energy could be stored chemically (e.g. in hydrogen, or hydrocarbons produced from them) and transported like LNG across an ocean.
The claim of 95% round trip efficiency is basically relevant if the the energy is to be consumed (or placed on a grid) near the point of production. Otherwise 65% (13%/20%) efficiency for chemical energy that can be physically transported is not too bad.
Hydrogen is a battery from the perspective of a renewable energy system. If it is produced as a byproduct of a fossil fuel (as is commonly done) IMHO, it is not a renewable resource at all. Producing it from solar PV is a completely different kettle of fish.
However, I see one big down to hydrogen. You can't tell how it was made, you rely on a promise that it's green, while it may actually be from methane... maybe with carbon storage, but you never know when that is gonna leak out. This might be a big loophole for fossil fuel corps / states
Tesla has been playing in that space too with their Megapack.
https://www.tesla.com/en_AU/blog/introducing-megapack-utilit...
There was a pretty bad fire with them in Australia. https://www.reuters.com/technology/tesla-megapack-fire-austr...
I suppose it's relative, but it seems it's a very good thing that only one caught because
> A giant Tesla battery pack caught on fire at a building in Australia, and it took 150 firefighters and four days to contain the blaze.
https://www.msn.com/en-us/news/technology/after-tesla-megapa...
150 firefighters taking 4 days to put it out. It certainly could have been worse, but I don't think it's a stretch to say it was pretty bad.
Conversion efficiency is a different thing than storage efficiency or transmission efficiency.
Unless your gas tank is leaking, it's efficiency as a portable energy storage device approaches 100%, especially for modern vapor sealed vehicles.
100kwh of Solar energy generates 13.8kWh of Hydrogen, which is about 50% efficent thus generates 7kWh of DC
Going direct to DC is 23%, and the battery layer drops that to 20%, so 20kWh - about 3 times as efficient if you are using storage.
That's not bad, there are many applications where you'll take the extra land/solar take to provide the flexibility and density hydrogen can provide. Sure not for normal grid connected and static usage, but for mobile and temporary usage.
And that's not to mention all the other uses of hydrogen in industry that, without this method, would have to be generated by Sun->DC->Electrolysis
I'd really like to see some citations with specifiic BOMs of equipment that can accomplish this, because the datacenter industry would like to have something like that, but it's my understanding that the efficiency is nowhere near that 98-99% figure.
That's not an argument for anything, and doesn't have anything to do with the article.
Lithium iron phosphate is lithium-ion. What Tesla is doing is changing the cathode material from Lithium nickel cobalt aluminium oxides (NCA) to Lithium iron phosphate (LFP). Other cathodes materials include LMO, LCO and NMC.
NCA has the best energy density, LFP is the best in everything else, including price, NMC is somewhat in the middle and LCO and LMO are becoming obsolete.
The sun basically provides unlimited energy, so efficiency isn't as important.
All of the hottest utility-scale storage technologies have really quite poor round-trip efficiency, but it doesn't matter. Lower efficiency requirements so radically reduce the system cost that you add more cheap generating capacity on top, and come out ahead.
There is not now, and never will be, any shortage of available land area for solar panels. Almost every place you can think of to put them improves the place. On a reservoir, crop land, pasture land, canal, they reduce evaporation, and run cooler than in the desert. On crop and pasture land, they reduce heat stress and water demand in the plants, improving yield and irrigation efficiency. On roofs and parking lots, they slow sun damage. On parking lots they even keep the rain off.
For aviation, LH2 has such fantabulous efficiencies that we can expect to see all serious air transport switched over by 2050 (providing civilization doesn't collapse first).
> As you can see, every low-carbon alternative raises costs more than 50 percent above baseline. The only ones that don’t raise it more than 100 percent are CCS (of the heat source only), blue hydrogen, or resistive electric in places with extremely cheap and plentiful carbon-free energy.
> The alternative that climate hawks would most prefer, the carbon-free option that would work best for most applications, is green hydrogen. But that currently raises costs between 400 and 800 percent. Ouch.
Green hydrogen is by far the most expensive option. 3-4 times more expensive than electric heat. That's the direct opposite of "the real reason we need “green” hydrogen now is for making [...] cement".
This new work will hopefully make green hydrogen cheaper. But if you're using electricity to make that hydrogen, i don't think it can ever be cheaper than electric heating.
Another thing. I think we should question any plan that requires more mass mineral extraction than necessary. It's not as if mining is an environmentally neutral thing, and there is more to restoring our planet that just getting surviving climate change.
Really brilliant as the UK will be way ahead in global production.
There's a good YouTube video explainer, search "just have a think blue hydrogen"
Here's government link
https://www.gov.uk/government/news/uk-government-launches-pl...
To fuel aircraft efficiently, you want a great deal of LH2. Anywhere LH2 aircraft fly, kerosene-fueled aircraft will be simply unable to compete. That will start on major international routes, with airports synthesizing LH2 on demand from grid power, banking it when spot price is lowest. The only thing that will save carriers loaded up with kerosene craft is the limit on how fast the LH2 aircraft can be manufactured.
Carbon-neutral steel production will depend on really huge amounts of H2, in place of coal or natural gas. Existing fertilizer production lines can inject H2 with the natural gas, and increase its fraction as more becomes available. At some point, as the carbon fraction decreases, electric heating will become more economical than burning injected gas for heat. Ultimately, improving catalysts will make the whole process more efficient than ever.
NH3 made with green hydrogen is a likely fuel for retrofitted long-distance shipping, where ships need only new fuel tanks and plumbing to switch over. Probably legislation will be needed to drive this change fast enough.
Cars with high-pressure H2 tanks are beginning to be practical, and are much lighter and cheaper to make than lithium-battery cars. When the car is lighter, the motor and drive train can be lighter too, and it takes less energy to accelerate them. In the short term, though, batteries are clearly winning. It is hard to be sure which will win, long term, but batteries have a huge first-mover advantage.
You can burn H2 directly in a natural-gas plant, or mixed into natural gas. So, as H2 production capacity grows, an increasing fraction of gas input to these systems will be H2. Ultimately, fuel cells driven from pure H2 will start to take over as prices of improved catalysts fall.
For utility-scale storage, bulk underground H2 is a much simpler and more reliable proposition than millions of battery cells, even though round-trip efficiency is poor. As top-line generating cost plummets, efficiency matters less. All the hottest storage systems (iron-air, hydrogen) are low roundtrip-efficiency.
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From what I understand, one of the biggest issues with trying to replace commercial cross-country jets [1] with electric alternatives is due to the fact that there isn't enough energy density in a battery to make that possible, and as a result, airplanes are a huge polluter towards climate change.
Would it make more sense to try and make hydrogen jets, at least if we can make the hydrogen relatively efficiently?
[1] I know jets really only make sense with fuel, replace "jet" with "big airplane"
Is there enough O2 at plane levels for fuel cells?
A hydrogen plane would have to be designed from the ground up.
This is true on a relative basis: flying across the US puts out a lot of CO2 for a single person.
But on an absolute scale, it's pretty tiny: 2% of total CO2, 12% of transportation CO2.
That's also why an air travel emissions factor is used by policymakers when talking about its effects.
(Also, US transportation emissions in other sectors, especially road, are enormous in comparison to other countries, for context on the relative comparisons: https://www.statista.com/statistics/1201189/road-transport-s...).
It probably makes more sense to just synthesize longer hydrocarbons.
Sorry, ignorance on my end is showing again; wouldn't a longer hydrocarbon still emit CO2 as a by-product since carbons are part of its makeup? Or does a longer hydrocarbon mean that there's a higher hydrogen-to-carbon ratio and therefore the pollution is less horrible?
You can also be carbon-neutral by making that cycle larger: extract carbon from trees, create fuel, burn it, and let new trees you planted convert the CO2 back into wood.
Not price competitive with fossil fuels, but then not much is - hard to beat ‘mega joules for free*’ as it were.
It’s hard to compete with “let everyone else in the world pay for the true cost of this energy”.
That’s what makes fossil affordable and why we need carbon taxes right this second.
Our current spike in natural gas and oil prices is something of a dry run for what carbon taxes would look like. So far it doesn't seem like the approval ratings of the governing party can survive it.
For aviation, sticking on a carbon that outweighs your hydrogens by almost 8x gives up a huge efficiency advantage. The efficiency advantage overcomes inconvenience of handling cryogenic LH2. My bet is the tanks will be nacelles slung under the wings alongside the engines.
The long answer:
* The question is moot until we have widespread decarbonization of the energy grid. Currently, our hydrogen mostly comes from steam reformation - splitting methane, CH4, into 2H2 + CO - which emits carbon dioxide. Once our electrical production is carbon-free, then we can think of producing hydrogen and powering vehicles with that. Electrolysis can serve as a carbon-free source of hydrogen, if the electricity is produced from a carbon-free source. There are more efficient forms of hydrogen production, like thermochemical hydrogen production with heat provided by nuclear reactors.
* Once carbon-free hydrogen production becomes available, then there's the question of building hydrogen powered vehicles. Hydrogen is the most energy dense fuel by unit of mass, except for nuclear fuels, but it's about half the energy density by unit of volume compared to hydrocarbons. Substituting fossil fuels with hydrogen is probably more feasible in container ships than aircraft. Hydrogen containment, be it pressurized or liquid-cryogenic, scales better at higher capacities as there is a better volume to surface-area ratio. Aircraft wings (long and skinny) are basically the worst shape for hydrogen containment. Past examples of hydrogen powered aircraft stored it in the fuselage [1], which would sacrifice cargo and passenger space.
* Lastly, for aircraft there's also the question of making engines that don't produce greenhouse gases. High-temperature hydrogen gas turbines will also produce nitrous oxides, which are greenhouse gases. This can be mitigated by running turbines at lower temperatures, but that reduces efficiency. There's also the idea of using hydrogen fuel cells to produce electricity to run turbines, but fuel cells and electrical motors don't have as good power to weight ratios as combustion turbines.
I'm much more optimistic about converting maritime transport to hydrogen fuels than aircraft. That said, the military is very interested in hydrogen planes. One of the limiting factors in modern naval warfare is fuel to fly planes. With hydrogen powered planes, a carrier could produce hydrogen with its nuclear reactors giving carriers an effectively unlimited source of aviation fuel. If they figure it out, hopefully the tech propagates to civil air transport.
It is not clear whether existing aircraft or designs can be usefully retrofitted for LH2. Existing wing tanks are, in any case, useless for LH2. You need much more room for LH2 tankage, and you might not want a big LH2 tank inboard; there are safety reasons for the fuel in current aircraft being out in the wings. So, maybe the LH2 is carried in nacelles slung under the wing, next to the engines. We will need to build up a great deal of aerogel manufacturing capacity to insulate them.
It is possible that existing wing tankage can be used to carry NH3 to inject, in small proportion, to minimize NOx pollution. Given a bit of surplus N, the N prefers to make N2, and the O prefers to make H2O. E.g., existing natural-gas plants inject NH3 to reduce their NOx output.
For shipping, anhydrous ammonia is probably a better choice of fuel. Existing engines can burn it, so you need only new room-temperature ammonia tanks and new plumbing.
‘Jets’ could make sense even without fuel if you consider that jet propulsion [2] is the generation of thrust using a fast-moving stream of fluid. Today’s jet engines are already turbofans [3] where only part of the propelled air passes through the fuel combustion chamber.
https://en.m.wikipedia.org/wiki/Powerpaste
It might pan out and reduce issues with hydrogen leakage
Thus for every hydrogen molecule you have to carry around 13 times the weight in magnesium oxide. Aka: This stuff is very heavy. Not exactly the thing you want on planes.
Moreover, the innovation here is that neither the solar cell nor the electrolyser require rare elements. As they say:
> Sustainable water electrolysis requires that the anode and cathode catalysts are noble metal free and contain small amounts of other metals in order to lower system costs and facilitate recycling.
As for efficiency:
> The measured [solar-to-hydrogen] efficiency is improved compared to all previous electrolyzers driven by low-cost [perovskite solar cells] that used solely Earth-abundant electrocatalysts but lower compared to the highest performing perovskite/Si tandem devices that uses noble metal electrocatalysts, which reached an initial efficiency of 17% [solar-to-hydrogen].
So this setup is less efficient than what we already have. But it doesn't require rare elements.
That's why battery EVs are so popular; they are clearly cheaper to drive per mile. Especially if you charge them cheaply from your own solar panels, using off peak grid rates, etc. You are basically driving almost for free. In some cases grid operators literally pay consumers to plug their cars in so they can offload excess energy. It's cheaper than shutting down gas powered peaker plants and having to restart them a few hours later.
The article is interesting because it proposes a way that gets production to less than 2x the efficiency difference relative to using solar panels to generate energy in terms of efficiencies (12-15% vs 20-25%). That's impressive. However, it says nothing about the cost of hydrogen because this is an academic article and not an actual product. However it suggests an improvement. For reference, producing hydrogen from wind energy would use about 3-4x the kwh in generated electricity to produce 1kwh of hydrogen.
That's not bad. But even (wrongly) assuming all of that would be converted to motion, that would be about a 3x cost per mile difference already vs. just putting the wind energy straight in your battery. Burning hydrogen has inherent inefficiencies (you produce heat and noise) similar to burning other fuels (20-30% efficiency would be pretty good). And even fuel cells are not that efficient; 60% efficiency is pretty good apparently. And if you are using hydrogen for fueling vehicles, what matters is the cost per mile. So, on top of the production that would be another loss of about 1.5 - 5x on top of the production inefficiencies.
The fantasy of hydrogen in cars and trucks is that it is needed and that the cost doesn't matter. The reality is that there are battery equipped vehicles in almost every weight and vehicle class being produced already with pretty awesome cost per mile that are going to be pretty hard to compete with using hydrogen. It's a no-brainer choice already for a lot of drivers and fleet operators. Sure, their range is not always that impressive. But at about 3-5x the cost per mile difference that's an inconvenience that can be worked with.
The other fantasy is that hydrogen is carbon neutral. The vast majority of hydrogen produced is grey hydrogen. If you want to save some carbon, fuel your car using methane instead of hydrogen. You'll produce a lot of co2 but a lot less than when you use that methane to produce hydrogen which you then burn or use in a fuel cell. That's the sad status quo of hydrogen on the road right now. What little there is neither green, efficient, or cheap. Making it green will raise the prices. Making it less inefficient is going to be a long battle, and until that is done, it will be inherently more expensive.
Green hydrogen when production of that is going to be more meaningful is still going to be useful elsewhere (aviation, shipping, heavy industries). And with wind and solar intermittency that basically means there are going to be surplusses (rather than shortages) because people will over provision to compensate. Hydrogen is a great way to use such excess energy. There's going to be plenty of demand for it. Just not on the road.
The pure oxygen is just as useful of a product and can be used to gasify woody biomass, plastics and other waste streams into more useful fuel sources such as syngas, or liquid fuels using the fischer-tropsch process. It is also useful for medical processes.
Second, natural gas lines can utilize something like 10% hydrogen...so we can store a large quantity in our existing infrastructure for use later that day, or in other locations.
we could use space rocks to heat water.
just saying.
It's already a problem in Eurasia with nation states using eg. natural gas delivery as a means to apply political pressure on other states, and this while it is still (relatively) easy to solve energy needs as carbohydrates can be easily transported.
If all border crossing energy/power delivery is through a physical network of cables, adapting if delivery is cutoff would be almost impossible unless all gas/coal/oil plants were kept at/near operating condition.
Hence, yes, the buildout must be some X times necessary power, as much as possible locally. A significant fraction of that generated power should be used to create a) industrial feedstock b) to generate liquids/gas that can be easily used and transported.
The latter in the case some nation is being pressured by energy blockades where the existing grid can not supply enough energy through transmission lines from other bordering states.
The fallacy in your argument is assuming there's a need for seasonal storage. That need would only exist if you rely exclusively on solar energy. Which of course people up north don't tend to do and people closer to the equator could actually feasibly do throughout the year.
Plenty of places get by mostly powered by different combinations of renewables. E.g. Norway (wind, hydro), Iceland (geothermal, wind), Scotland (wind, tidal wave power), etc. without a lot of storage.
We would not be contributing to the overall contribution of greehouse gases. Some arguments are diesel and friends are safer in storage and transportation than hydrogen.
Mostly it’s just economics. Either the costs need to come down, or oil prices need to rise.
The way oil prices are headed, that might not take long.
Hydrogen is just H2. Diesel is a complex hydrocarbon.
A viable future, would be a highly distributed network of hydrogen stations, with Hydrogen generated from solar energy, with enough reserve capacity to act as a base load plant.
Extracting energy from hydrogen is a well understood process.
They will bank hydrogen synthesized when grid prices are lowest, in mid-day, when immediate power need is vastly outstripped by solar generating capacity.
Hydrogen is not for use cases where there is an electric alternative. Electric almost always wins. But there are use cases where there is no electric alternative or none that is available any time soon, most notably chemicals and steel.
Look at the wayward Toyota, they seem to think they can navigate around chemisty to sell their EVs with a hydrogen fuel cell attached.
There is still use for hydrogen outside of vehicles (and possibly some highly specific scenarios involving vehicles).
Obviously, producing hydrogen from methane to power cars is a stupid idea if your goal is to reduce greenhouse gases.
However, pure electric cars are only successful in some niches, and larger vehicles like buses and lorries just aren't practical yet, whilst hydrogen buses are already a thing. Battery technology has come a long way, but the energy density is still absolute garbage when you compare it to the energy density in any fuel.
If you can produce hydrogen directly from solar power, then the overall efficiency may be less important: the advantages of greatly increased power density, and ease of refueling may make it more appealing.
For battery-powered cars to be the long-term solution, and not just a stop-gap measure, there will need to be a massive breakthrough, to the point that energy densities can be compared with other fuelds.
As petrol/diesel cars are phased out, there will be an increasing number of customers whose needs cannot be met by the current state of electric vehicles, and there will need to exist another option. At that point, maybe hydrogen won't look like such a bad bet...
In Europe, battery powered trucks can carry a heavier load than diesel trucks. The weight disadvantage of a battery powered truck is about a tonne. The batteries weigh a lot more than a tonne, but so does the engine, transmission and fuel in a diesel truck. The difference is about a tonne. In Europe, they allow battery trucks to weigh two tonnes more than diesel trucks, so... In America battery powered trucks have a 1000 pound weight limit increase.
Green hydrogen is always going to cost about 10x as much as electricity. Using electricity to electrolyze water, compress the hydrogen, transport the hydrogen, strip off the electrons in a fuel cell, charge a battery and then drive a motor is necessarily a lot less efficient than using than skipping 4 of those steps to charge a battery directly.
And truckers don't care about fuel density, they care about costs.
Compared to fuel yes. Compared to batteries, even at relatively low pressures, I think hydrogen still wins even by volume, and at higher pressures it's an order of magnitude difference.
> In Europe, battery powered trucks can carry a heavier load than diesel trucks.
You mean legally? If we're discussing which option is technologically superior long term, then it doesn't really make sense to argue based on arbitrary laws today. Is there a particular retionale behind the law that would make sense for electric trucks but not hydrogen ones?
> Green hydrogen is always going to cost about 10x as much as electricity.
Possibly, but as more renewable energy sources come online, the problem is going to change from "can we produce enough energy?" to "is the energy available at the right time and place?". Electrical energy is very difficult to store and transport in any significant quantity. We already have to turn off renewables sometimes because they're simply producing too much power when we don't need it. That power may as well go to creating hydrogen than doing nothing.
I don't know that hydrogen specficially will be the long term solution either (after all, something better could always materialize) but current battery technology is definitely not a panacea.
> ... is necessarily a lot less efficient than using than skipping 4 of those steps to charge a battery directly.
High battery/payload weight ratio means you need more energy to get where you're going, which is not typically considered when comparing the efficiency of batteries to hydrogen. Batteries also take a lot of energy to manufacture in the first place, and have a limited lifespan, which is also rarely considered. I think that with some minor efficiency improvements to a couple of steps, and a lowering cost of electricity at "off-peak" times, that the overall equation will shift.
> And truckers don't care about fuel density, they care about costs.
Costs come from a lot of places. Trucks sitting around charging instead of delivering goods are a cost. Reduced range means increased costs. Expensive batteries that have to be replaced every X years are a cost.
This is the most important point of the economics of renewables. Eg, I think Toyota was too early and applied to the wrong industry (personal vehicles), but not wrong.
For example, burning diesel for electricity (which is done a lot in remote areas and as backup) is really expensive, even just looking at the point of generation and not the externalities. If renewable electricity generation is hovering around the 2c per kWh mark, even with all the losses, H2 starts to make a lot of sense for a lot of energy intensive industries. Even more so when the electricity used to generate it was never going to get even sell for that price because it just wasn't needed.
Renewables have an economic problem currently where every solar panel and wind turbine added to an electricity network will have a lower ROI than previous ones due to their intermittent nature, lowering the return of older assets as well. As their use grows, this problem will get worse and generators will have this large earning potential with an asset generating wasted energy, with a life span measured in several decades. Long tail, lots of opportunity to do more with those assets.
But given how long it will take to build out to 3x renewable generation capacity and then auto makers to change, etc etc I don't think that will be for another 10+ years, but hope I'm wrong.
I think its time we start realizing that much of the "efficiency" argument is an exaggeration or a lie. EVs aren't that efficient especially in cold weather, and fuel cell cars aren't really that far off. The other big issue is the inability to capture excess renewable energy. As we keep on building out more renewables, we're finding out that curtailed energy is growing exponentially. Pretty soon the vast majority of renewable energy will just go to waste. Hydrogen allows to use that energy, but batteries won't. Combined with the huge resource requirements of batteries it's clear that this technology is primed for a major stumble.
There is also Hyzon, a fuel cell manufacturer that hopes to massively convert trucks to Hydrogen.
It can be described as Toyota having both eyes open whereas Tesla is blind in one eye, but still claiming that the latter sees better.
When the forklift went flat, you got another forklift to remove the battery and replace it with a fresh one.
Tesla tried this once and it wasn't a great success however, if you have a depo with a stack of batteries, you run a fleet of trucks, this makes a lot more sense.
It's something I'm suprised hasn't been floated as a lot of the customers for the electric trucks are fleet customers
https://toyota-forklifts.eu/solutions/energy-solutions/what-...
State of the art electrolyzers are run at 1000x current densities. That roughly means 1000x installation cost.
The best use cases for hydrogen are fertilser or in hydrocracking. We currently use primarily natural gas to produce hydrogen.
Urban or commuter cars are one of the worst use case for hydrogen. Electricity and batteries are way better.
That's how un-scalable long-term battery storage is. Hydrogen is more so: you can store hydrogen in vast quantities in salt caverns, and move it around. Pumped hydro is best, but sites are limited. Compressed air is another solid contender.
Turns out that pumping water up-hill and running generators when the water flows backwards is a very efficient energy storage mechanism.
Do you mean 10% of the generation on a typical summer day? Or 10% of the generation of an entire summer?
The problem with this kind of calculation is that battery technology (and cost) is very much a moving target.
LFP would probably be the better choice today. It's cheaper, safer, and can handle far more load cycles. That comes at a cost of a lower energy density, but that hardly matters for utility scale batteries. Tesla's megapacks use LFP already - https://cleantechnica.com/2021/05/11/tesla-transitions-to-lf....
Like you say, there are many other energy storage options like pumped hydro, compressed air, etc. My personal favorite is the train full of concrete that goes up and down a hill (https://interestingengineering.com/concrete-gravity-trains-m...).
My opinion is that we need a mix of energy sources and we need a mix of energy storage solutions.
Falling battery prices helps of course but we are very far from a point where we can eliminate the need for hydrogen.
A 10k km HVDC line is enough to draw power from places 90 degrees apart in terms of latitude. Similarly, between the east and west coast of the US there's around 3h of a time difference.
Chile is planning on building an even longer cable, so it's entirely in the realm of possibility:
https://www.pv-magazine.com/2021/11/15/chile-wants-to-export...
This is about splitting water using electricity. You can create and use the fuel at the same site. Just need a water pipe and a connection to the grid. Splitting off hydrogen at a separate site is just wastefull.
My point is create an energy storage station, all you need is water and grid power. No pipelines needed. This hypothetical power storage site would generate hydrogen during the daytime from surplus grid solar, then burn the hydrogen at night delivering the power back to the grid.
To be clear, I'm not necessarily talking about a solution for homeowners. An energy storage facility could cheerfully be as large Diablo Canyon Power Station. It just depends on the efficiencies of everything from the water-splitting process, storage solution, grid losses, and grid capacity.
I imagine the cost of hydrogen storage is significantly less than batteries, thereby offsetting the reduced efficiency of turning solar power into electricity. The main issue we have with solar is storage for when the sun isn't out.
does it mean there's a "mean solar-to-fuel conversion" to look for ?
The issue with doing something useful with it is compression and storage.
While compression is easy, purification is an issue. With certain lower percentages of purity (from very rough memory under 92%, but could be in the 99s) it becomes an explosion risk.
Consider a 25% efficient solar panel -> 50% electrical efficiency to convert H2O into H2 + O2 == 12.5% total efficiency (and a 25% efficient solar panel is a high-end panel). So this design discussed is probably better than the status quo.
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There are internet flame wars over the future of energy and energy storage.
Lithium Ion batteries are one form. Hydrogen is being proposed as a fuel of the future (with Japan showing off Hydrogen torches all over the Olympics earlier this year, as a lot of Japanese companies are pushing Hydrogen as a future fuel)