> Turning electricity into hydrogen and then into motive power for a car is dramatically less efficient than using a battery

This is true —- but the total quantity of battery storage potential is utterly dwarfed by the storage potential for gas, in subsurface storage reservoirs and salt caverns. You can store days worth of energy in batteries; you can store a winter’s worth of energy in gas.

It’s not a matter of efficiency, it’s a matter of quantity. We do not, and will not, for decades, have the kind of battery storage required to support the grid.

Storing hydrogen is substantially harder than storing stuff like methane, or CO2, or even O2.

Hydrogen's atoms are so small they try to pass through the crystalline lattice of metals, making the hydrogen-enriched layer which is more fragile [1]. Your regular polymer hoses are much more permeable to hydrogen.

Hydrogen gas burns with entirely infrared flame, not visible to human eyes [2].

Hydrogen, even highly compressed, is still very lightweight, so storing significant amounts requires either very high pressures, or liquefaction. Liquid hydrogen requires an uncomfortably low temperature of 20K, but starts to freeze into solid state at 14K.

Hydrogen is the most efficient rocket fuel, there's no denying. For all other fuel applications, it's pretty problematic.

[1]: https://www.osti.gov/servlets/purl/1727338

[2]: https://spinoff.nasa.gov/spinoff1997/ps1.html

Which is why the current proposals to significantly expand the global per annum hydrogen production via green solar hydrogen production are looking to transport Ammonia (Three Hydrogens and a Nitrogen) across the planet for use in large baseload generators.

Less storage problems, more options (higly compressable gas, or pure liquid, or "liquor" (dissolved)), and no mucking about with fuel cells.

Just straight up movement of energy (with losses to be sure) from places with an excess of sunlight to those that are short.

What's the benefit of ammonia vs. turning hydrogen into methane via carbon capture?

Carbon capture is hard, nitrogen is truly abundant. That is unless you happen to have a source of highly concentrated CO2 at hand. Which is certainly true now, but won't be in the endgame. Methane (or something with an even lower H-per-C) will surely be part of the picture, but it can't be the mainstay. I'd expect hydrolizer capacity to cluster around storage opportunities (like salt caverns) within convenient grid range from energy sources, large ammonia plants to continually work from that hydrogen buffer and higher-value H2 consumers to opportunistically tap into the same buffer whenever their "other ingredient" is available. That "other" could be metal ores, iron oxide returning from an oxidization energy cycle or CO2 from biomass burning or waste incineration. But there's always hydrogen as a first step, and the (centralized within grid range) hydrogen storage as the buffer that solves the dispatchability problem.

Fun observation: If some of the hydrocarbons created this way make it into plastics that isn't passed back into incineration (or a better form of recycling) you'll have true carbon-capture for the fraction of the carbon that came from biomass. Without we trying.

Thanks for the detailed reply

This. Is there even one power2anythingelse that does not have hydrogen as its first step? Hydrogen storage will be important, as the input queue for whatever step comes next so that only the hydrolysis capacity has to be scaled for being able to take in supply peaks and idling the rest of the day/week/year. But hydrogen storage won't be involved at all anywhere in transportation or distribution of energy (with a few possible exceptions in large very high energy density requirement applications, I wouldn't completely rule out hydrogen aircraft being less infeasible than e-fuel powered aviation at scale)

Hydrogen is far more energy dense than batteries. For example: for a 800km truck, the difference can be as much as 2 tonnes. https://www.umicore.com/en/newsroom/news/fuel-cells-battery-...

Also, 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...

In terms of cost, it is also now possible to use Boron Nitride for storing hydrogen - very cheaply and very safely.

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

> not obviously any better than importing LNG or oil

True, because transporting hydrogen is obviously much worse than transporting LNG or oil. Hydrogen is an impossibly huge pain in the ass, and should be avoided if at all possible, because

Hydrogen

leaks through the smallest gaps.

burns in concentrations ranging from 4 to 74 percent.

burns clear in daylight.

reduces the ductility of metals exposed to it (embrittlement).

has shit energy density to boot.

Japan's plan has been to import hydrogen. Probably from Australia.

Nuclear is unpopular since Fukushima, and Japan doesn't have great renewable resources. The country is extremely land constrained -- and although the "renewables require too much land" argument is silly on the American Great Plains, it does hinder Japan.

Additionally, the solar irradiance is mediocre, and their offshore wind would have to be truly floating wind turbines (which are more expensive) because the continental shelf drops away so quickly.

If you can manufacture pure hydrogen by hydrolysis from Australia solar power, then they should go the next step and create methane (CH4). If you can extract carbon from CO2, that would be a crazy good win. (Probably horribly energy inefficient, but that is the future, I guess.) Anywhere with huge deserts and access to ports can become rich on this path: India, Chile, Australia, North Africa, Middle East. (China has big deserts, but very far from ports.)

People are talking a lot about batteries in this HN discussion, but there are industries that are so much simpler to run on burning gas/coal (steel, petro-chemical, etc.). Japan has massive heavy industry, similar to Germany, that 100% depends upon imported methane. Someone also told me (not sure if true) that the infra required for hydrogen is much more expensive than methane because it is "more leaky". Thus, equipment tolerances are way higher for pure H2 vs CH4.

Last: The "we don't like nuclear" view will only last until the next energy crisis. The current PM (Kishida) is already talking about re-activation. Yes, there will be billions to spend to upgrade existing reactors, but Japan never shies away from infra spending! It doesn't get much attention in the media, but plenty of infra (bridges, tunnels, etc.) was upgraded after the 2014 earthquake.

Japan’s government actually just decided to revitalize nuclear power and support among the population is growing.

And, FWIW, Japan plans to use high-temperature nuclear reactors to produce hydrogen with very high efficiency.

See: https://www.jaea.go.jp/04/o-arai/en/research/research_03.htm...

Green hydrogen is made from electricity. The cost of green hydrogen is currently high, but it is dropping faster than pretty much any other energy storage technology. Hydrogen storage is an order of magnitude cheaper (or more) than any other tech. It is expensive because of the cost of electrolyzers/fuel-cells that convert between electricity and H2. These costs are dropping fast at efficiencies of 80%+ along with the cost of solar and wind. If you project the cost declines into the future the economics of producing hydrogen at remote solar wind farms, generating hydrogen, and transporting the H2 by tanker or pipeline are compelling.

Abu Dhabi already sells solar electricity for 1.35 cents/kWh. That price will drop by at 3-5x as solar reaches maturity. Natural gas plants sell power for ~6cents/kWh. Green hydrogen will have at least 5.5cents/kWh ($1.80/kg) of wiggle room to generate returns.

Many people consider batteries to be superior to hydrogen for all business cases. This isn't true for applications that need more than ~10 hours or so of capacity. Sub 10 hours is a huge market and encompasses almost all transportation, but there is a vast market for storage beyond 10 hours.

The Achilles heel of batteries is that the power of the battery and the energy stored by the battery are linked. An Li battery can easily discharge itself in one hour. If you want 10 hours of storage you need to buy a battery that could deliver 10x the power you're asking it to. This dramatically increases the cost and sheer tonnage of materials required to make the required system. Green hydrogen systems only require equipment that can deliver power at 1x the requirement with a storage tank that holds 10 hours of fuel. This means that there is always a crossover point where hydrogen becomes cheaper than batteries. My projection for the future is that this number will be around 10-20 hours.

This makes hydrogen the best choice for many applications and is the reason why lots of governments are into the idea. Transportation is only around ~20% of the energy we use, much of the rest might come from renewable hydrogen in the future.

Japan plans to make hydrogen using high-temperature nuclear reactors (HTGR or HTTR).

See: https://www.jaea.go.jp/04/o-arai/en/research/research_03.htm...

High temperature hydrogen electrolysis is a proven cheap tech. The main problem is the cost of nuclear in my opinion.

While one could easily do arm chair criticism the author of the top article thought it more convenient to just ignore it?

Nifty. The chemical process involved appears to be:

https://en.m.wikipedia.org/wiki/Sulfur–iodine_cycle

50% thermal efficiency from nuclear to hydrogen sounds very good.

Except nuclear steam generators have to run at well under 830 degrees and at low head because of two loop cooling and corrosion issues so odds are pretty good this will be about as reliable as every other gas cooled reactor and be shut down in 10 years.

Unfortunately 'green hydrogen' currently isn't.

"Under baseline conditions, the greenhouse gas (GHG) emissions are around one-quarter that of the currently dominant process for hydrogen production, steam methane reforming (SMR). However, sensitivity analysis shows that GHG emissions may be comparable to SMR under reasonably anticipated conditions. "

https://pubs.rsc.org/en/content/articlelanding/2021/ee/d1ee0...

I think this type of analysis fails to project the future. GHG emissions from solar cell production will decline as the inputs and processes used to make them begin to use renewable energy.

Green hydrogen decouples H2 generation from hydrocarbons, and industrial uses of H2 will be critical in decoupling more processes and industries from fossil fuels. That's the whole point.

The other part of the abstract suggests that grid energy will be required to buffer intermittent renewables. This argument assumes that it is not possible to design H2 electrolyzers that can rapidly adapt to a change in electrical input, which is simply a relatively straightforward engineering challenge.

I find it hard to believe that the authors of this paper didn't already know all of this.

»Turning electricity into hydrogen and then into motive power for a car is dramatically less efficient than using a battery, and car commutes in Japan are on the short side, so huge batteries wouldn’t be as necessary.«

Which is why Japan is favoring high-temperature hydrolysis here using high-temperature nuclear reactors.

See: https://www.jaea.go.jp/04/o-arai/en/research/research_03.htm...

>This doesn’t make sense to me. Hydrogen is not an energy source

Hydrogen is often compared against batteries. Those aren't an energy source either. I haven't seen anyone seriously propose hydrogen based powerplants. I have seen plenty talk about hydrogen fuel cells as a potential alternative to BEVs and a potential way to get around the multiple short comings of lithium batteries. Fuel cells of course have their own problems. But we've yet to come up with an alternative to gas engines that are as long ranged, quick to fuel, reliable, cost effective, safe and performant while also being net zero or negative carbon.

>So the only way this seems like a win for Japan is if electricity were cheap, battery EVs were not economical, and the loss associated with electrically synthesized hydrogen didn’t matter.

I feel like you are handwaving the issues with BEVs while focusing on the issues with hydrogen. I'm not sure which at the end of the day will turn out to be better. But right now BEVs are incapable of becoming the defacto solution for the simple fact that the battery packs wear out and replacing them will total the car. You can't develop a working used market this way. And lower income individuals simply can never afford to use them. The fact that car markers are going out of their way to design platforms with batteries that are difficult to replace exacerbates the problem. But even if they were easily swapped, their high cost and the fact they are tied to the vehicle means a large chunk of the market can't afford them. And nobody is talking about this.

> I haven't seen anyone seriously propose hydrogen based powerplants.

Well, Japan has. You may have read about it recently in the article linked at the top of this comment page. Here's another source from Japan itself: https://www.meti.go.jp/english/policy/energy_environment/glo...

> Accelerating the commercialization of hydrogen power generation turbines in Japan by supporting the early demonstration with actual equipment, with a view to capturing the global market in the future

> Assuming that the price of the 100% hydrogen-derived electricity retail menu and the price of the 100% natural gas-derived electricity retail menu are the same, and assuming that only the latter retail menu has a price hike of about 1.8 yen/kWh (based on the time when the cost of LNG-fired power generation was at its highest), a standard household would be able to save about 8,600 yen/year.