[ForHackernews]

Why is it such a terrible idea? In theory you can generate it via electrolysis in places with plentiful renewable energy, and then you've got a very high-density, lightweight fuel. On the surface, it seems ideal for things like cars or planes where vehicle weight matters. Batteries are huge and heavy and nowhere near as energy dense as gasoline.

[ssl-3]

Ignoring some of the other issues:

Imagine we have this electrolysis plant, splitting up water to produce the hydrogen we need for an area. That's fine.

But it needs fed electricity to keep the process going. Lots of it. It needs more electrical power to split the water than combining it again produces.

So it starts off being energy-negative, and it takes serious electricity to make it happen. Our grid isn't necessarily ready for that.

And then we need to transport the hydrogen. Probably with things like trucks and trains at first (but maybe pipelines eventually). This makes it even more energy-negative, and adds having great volumes of this potentially-explosive gas in our immediate vicinity some of the time whether we're using it individually or not.

Or: We can just plug in our battery-cars at home, and skip all that fuel transportation business altogether.

It's still energy-negative, and the grid might not be ready for everyone to do that either.

But at least we don't need to to implement an entirely new kind of scale for hydrogen production and distribution before it can be used.

So that's kind of the way we've been going: We plug out cars into the existing grid and charge them using the same electricity that could instead have been used to produce hydrogen.

(It'd be nice if battery recycling were more common, but it turns out that they have far longer useful lives than anyone reasonably anticipated and it just isn't a huge problem...yet. And that's not a huge concern, really: We already have a profitable and profoundly vast automotive recycling industry. We'll be sourcing lithium from automotive salvage yards as soon as it is profitable to do so.)

[aunty_helen]

It’s not even the grid, by the time you’ve done the electrolysis you’d be better off just charging a battery.

Also, compressing and cooling a gas takes another huge hit at the efficiency. Electrolysis comes out at atmospheric pressures.

Oh and the platinum electrodes you need…

I’m also just now visualising a hydrogen pipeline fire… terrible terrible idea.

[stephen_g]

It’s horrible to work with - dangerous, embrittlement issues etc., and very energy intensive to compress into very heavy cryogenic storage containers…

[amelius]

Yeah it is so bad that it is common that rockets are launched with a hydrogen leak here or there.

[credit_guy]

> dangerous

It is actually less dangerous than other fuels, for the simple reason that it is extremely light and buoyant. A gasoline fire is bad, because the gasoline stays where it is until it fully burns. A hydrogen fire is less bad, because it will tend to move upwards.

[loeg]

It's hell to store. The energy density is terrible and as a tiny molecule it escapes most seals. When it transitions from a liquid to a gas, it expands manyfold (i.e., explodes).

[nkoren]

Zubrin's "Hydrogen Hoax" from 2007[1] is basically an ironclad critique. The physics are inescapably poor, and always will be. (Zubrin makes other points in that article which should probably be taken with more salt, but his critique of hydrogen stands).

1: https://www.thenewatlantis.com/publications/the-hydrogen-hoa...

[CamperBob2]

Besides being expensive to generate unless you already happen to have an electrolysis plant handy, hydrogen is awkward and hazardous to store. Once generated, it costs yet more energy to liquefy, and then it seeps right through many common metals, weakening them in the process. It's just not a good consumer-level energy source, and nobody could figure out why Toyota couldn't see that.

Interestingly, liquid hydrogen is nowhere near the most energy-dense way to store and transport it. I don't recall the exact numbers but absorption in a rare-earth metal matrix is said to be much better on a volumetric basis. [1] Still not exactly cheap or convenient, but it mitigates at least some of the drawbacks with liquid H2.

1: https://www.fuelcellstore.com/blog-section/what-hydrogen-sto...

[fuzzfactor]

The rare earth metal matrix can be a bit more optimized and I think progress is being made.

Why wait though ;)

With common metals hydrogen fits in between the matrix naturally to an extent.

Not like for efficient storage though, just the embrittlement, which gives researchers even more challenging things to be careful about.

[smcin]

Remember that China briefly embargoed Japan for rare earth metals in 2010, and Toyota launched the Mirai in 2014. My theory was that it was developed as a national fallback for Japan in case that embargo continued or got worse. Think 1930s Volkswagen. Anyone can comment on that?

[fuzzfactor]

>you've got a very high-density, lightweight fuel.

Correction, a very low density, lightweight fuel.

Burns clean though with no carbon in the exhaust.

But the upstream carbon emissions have not come close to zero when you look at total hydrogen use in the real world so far.

[Rygian]

Check out the "Clean Hydrogen Ladder" document.

Hydrogen wastes a large amount of energy.

[cbmuser]

Unless you produce it using the Sulfur-Iodine cycle in a high-temperature nuclear reactor.

See: https://en.wikipedia.org/wiki/Sulfur%E2%80%93iodine_cycle

and: https://www.jaea.go.jp/04/o-arai/nhc/en/research/hydrogen_he...

[L-four]

The cheapest way to make hydrogen is to use fossil fuels.

[SideburnsOfDoom]

Hydrogen is the minimum viable atom: one proton, one electron. H2 is a tiny molecule. "hydrogen embrittlement" is when it's small enough to diffuse into solid metal, because it's that much smaller than iron atoms.

It's hard to work with because of this, and what's the point? For most uses, electricity supply is already everywhere.

[Qwertious]

>Hydrogen is the minimum viable atom: one proton, one electron.

Wait until you hear about H+