[AlexandrB]

And Green is a huge efficiency loss. I suppose if the energy used to do it truly "green" and "surplus"...

> As of 2022, commercial electrolysis requires around 53 kWh of electricity to produce one kg of hydrogen, which holds 39.4 kWh (HHV) of energy.

https://en.m.wikipedia.org/wiki/Electrolysis_of_water

[wisty]

20% loss isn't really "huge", is it?

10% of power is lost to distribution anyway. Batteries can also lose 10%.

The issue with hydrogen isn't producing it, it's that it's an absolute nightmare to transport and store. Hydrogen can soak into metals, causing them to become brittle - https://en.wikipedia.org/wiki/Hydrogen_embrittlement and it leaks if there's absolutely any chance of it possibly leaking (thanks to the small molecules, and its tendancy to cause everything it touches to go brittle), and can cause a very big bang if it does leak.

It might work well for planes (where power to weight is at an absolute premium) but for cars and buses the weight of a bigger but tamer battery just makes more sense. It's absolutely a good rocket fuel.

The issue isn't that it can't be green. The issue is that it's rocket fuel - high performance but dangerous and high maintenance. Putting rocket fuel in a bus is just dumb.

[theshrike79]

But then you have even more losses when you convert the hydrogen back to energy.

The formula is that 55kW of electricity used to generate hydrogen from water and then converted back to electricity in a gas turbine or fuel cell results in 15kW of energy.

That's a lot more than 20%.

Compare that to just storing the 55kW in batteries and using them to spin an electric engine. "Hydrogen economy" only makes sense if you have infinite free electricity or massive overproduction.

[ben_w]

> "Hydrogen economy" only makes sense if you have infinite free electricity or massive overproduction.

Or when batteries are really expensive and global production and/or geopolitics prevents a global power grid.

Both were the case 15 years ago (and geopolitics still prevents a global power grid today, but metal production has increased and is now sufficient).

Hydrogen wasn't entirely stupid back then; even though PV was more expensive than today, the trends were already clear.

Now? I think hydrogen is suboptimal for most users. But I wouldn't bet against the idea of someone, somewhere, likely in the arctic or antarctic circles, deciding that they really do need multiple months of energy storage, and for those specific weird edge cases I think it's at least possible they might decide a cryogenic liquid hydrogen tank the size of the space shuttle external tank, refuelled every summer by a comically large PV array that works 24 hours in some days, is less silly than 3 gigawatt-hours of batteries.

[thfuran]

And don't you lose a significant amount compressing it for reasonable storage as well? Or is that considered part of the generation loss?

[theshrike79]

That's calculated in the total losses. You either need to compress it or freeze it. Usually for vehicles it's compressed, for long term storage or transfer it could be either.

[Loudergood]

Ok now added hydrogen losses due to distribution and storage.

[cjbenedikt]

Frequently the green energy used to split water is "surplus" energy. For example the bulk of offshore wind energy happens between 10pm and 2am when energy demand is at its lowest. That energy goes to waste if not stored in hydrogen. Hence, efficiency is irrelevant.

[SoftTalker]

When the energy is free (solar) efficiency doesn't matter, or at least not nearly as much.

Same reason the mob could sell their hijacked goods under wholesale prices... it was all profit no matter what.

[486sx33]

Then force all electric cars to be charged only by solar!