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Comment by hanniabu | Hacker News Reader

Makes much more sense to keep striving for electric solutions so our whole infrastructure can be uniform.

As long as you don't get your hydrogen from natural gas it's just energy storage like batteries. You can make it from electricity or directly via solar-powered reactions.

That's pretty much irrelevant, though. The infrastructure for energy distribution is decoupled from its production. Even if hydrogen is split from water via gas today, it can be done by solar or wind tomorrow with no changes to the distribution network.

Current hydrogen production is largely from cracking methane, where natural gas is the feedstock (and also energy source) - it is much cheaper than production from electrolysis.

>As long as you don't get your hydrogen from natural gas (...)

And that's the problem: hydrogen production is a huge waste of energy. Well to wheel efficiency of fuel cells is 22% vs 73% for battery EV (source: https://twitter.com/transenv/status/899976235794788352/photo...)

I can't speak to well to wheel, but at the very least current research tech electricity to hydrogen to electricity round trips are 75% efficient.

https://www.nature.com/articles/s41560-019-0333-2

But BEV cannot really use intermittent energy sources. Not without severely inconveniencing drivers and that's impossible. Hydrogen could be made from intermittent energy sources.

How efficient is hydrogen as an energy storage medium compared to e.g. Li-Ion batteries?

Efficiency as in energy/kg?

Tesla batteries: 207 watt-hours per kilogram (per google search)

Hydrogen: 120-142 MJ per kilogram (per google search)

Conversion from MJ to watt-hours: 277.778 watt-hours per MJ

120*277.778/207 ~ 161 more compact. Assuming energy conversion losses are equal.

Efficiency in terms of watts out from the medium divided by watts into the medium over a normal duty cycle.

As I said in another comment with some napkin calculations is about 30%. Another user gave a 22% number compared to 73% for batteries. The difference is hugely in favour of batteries.

trying to split the difference between https://en.wikipedia.org/wiki/Toyota_Mirai https://en.wikipedia.org/wiki/Tesla_Model_S https://en.wikipedia.org/wiki/Tesla_Model_3

I mean different shaped/sized cars and all but probably a bit worse? range vs weight seems about on par with the S but worse HP?

but also https://en.wikipedia.org/wiki/Fuel_cell#Theoretical_maximum_... so ?

Hydrogen is 3x more energy dense than diesel, and diesel is about 5 to 10x more energy dense than lithium ion batteries.

By mass or volume?

Mining and processing Lithium isn't that clean either.

There isn't enough infrastructure to support all electric transportation, yet. Also not enough cobalt for the current battery technology.

If you need to build additional infrastructure, why not use a technology that can "recharge" a car within minutes instead of hours?

At least in Germany, the electric infrastructure is mostly up to the task, switching to all electric cars would take only minor improvements, mostly adding more local transformers as the electricity/household is going to raise most of all. Overall, it would mean a mere 20% of more electricity consumed. Also, as charging is a nicely controllable load, electric cars could stabilitze the grid.

Modern electric cars can be recharged in well under an hour, so "hours" is off - unless you charge over night, where it doesn't matter.

For hydrogen on the other side, you would need a complete new infrastructure. Hydrogen fuel stations have nothing in common with conventional gas stations and are really expensive ($1 million/pump). Also, there are restrictions in setting them up in residential areas and while you might be able to refuel a hydrogen car in not much more than 5 minutes, there is a dead time in which the pump cannot serve the next car until the internal pressure has been restored (like 15 minutes).

This is absolutely false. There are currently discussions about net instability due to the missing North-South connection for renewable energy sources. I think you underestimate the sheer amount of power needed for cars, especially in the densely populated southern areas.

This is NOT "absolutely false". There are no net instabilities. Yes, there are lacking north-south connections and they are being built. But they don't have to do with the net capacity as such. They have to do with the new requirement of distributing wind energy from the north to the south and solar energy northwards. This was previously not needed, as every country roughly generated enough energy for their needs and there was little far-distance transportation.

And I don't understimate the amount of power needed for cars, it can be easily calculated, as the numbers of the cars are known as well as the average distance travelled per car. Do the multiplication and you get about 120 TWh of electricity needed per year. That is for converting any single car to electric. Which will take more than 20 years from now on. Compare that to the 600 TWh of production.

This doesn't even calculate in all the electricity spent on fossile fuels, which would be saved.

If you need to build additional infrastructure why not use a technology that's used already.

The charging issue will be solved. There's lots of theoretical and lab proven work showing it can be done and will be achieved.

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