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).

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.

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.

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.

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.

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.

Why would this be desirable?

/s, mostly

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.

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.

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.

We can make methane, which is a lot easier to store than hydrogen.

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

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

I'm not as pro-Hydrogen as you but I see some potential benefits for sure :-)

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.

https://xkcd.com/793/

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.

---------

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'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.

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)

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.

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.

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.

> 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.

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.

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.

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.

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.

Yes, but this is changing and there are a number of very interesting options.

https://en.wikipedia.org/wiki/Lithium-titanate_battery

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.

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.

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.

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

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.

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

That's not an argument for anything, and doesn't have anything to do with the article.

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.

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.