[0] I’m not a civil engineer and I can’t estimate the costs of upgrading existing methane pipes to cope with hydrogen, but people write about it being a thing, so this may or may not be better than pure hydrogen even if it’s less energy efficient; but the point is there are many options not just two
- batteries: not available large-scale
- thermal storage: potentially terribly inefficient (but as I said, yes it's at least something!)
- pumped hydroelectric: where I'm from, only available to a tiny fraction of the country
- Sabatier process methane: that's a possibility I guess, more inefficient though
My point being, yes you're right, there's many more storage solutions, but hydrogen seems to trump most. Might as well use that as much as possible.
> [0] I’m not a civil engineer and I can’t estimate the costs of upgrading existing methane pipes to cope with hydrogen, but people write about it being a thing
The issue is also that the recipients would need to deal with the pure hydrogen they're getting. Residential boilers for natural gas can't, for example. New models are required.
And all of this is fine until we get to ~95% clean/renewable grids. Maybe at that point it’d be worth using hydrogen fir seasonal storage. But even then, you’ll still have some curtailment because otherwise your electrolyzer is too expensive.
Check out https://model.energy for how this would work.
Nevertheless, transitioning grey hydrogen to blue hydrogen is probably a good thing. There's a lot of demand for hydrogen already in various industrial applications that are currently mostly using grey hydrogen. And transitioning more of our industry to hydrogen is key to de-carbonizing it. So, whether we like it or not, the hydrogen market is going to grow a lot in the next decades and it is probably going to be mostly blue+grey hydrogen for the foreseeable future produced by oil and gas companies and only little bits of green hydrogen.
The problem with green hydrogen is that it is magnitudes more expensive than blue hydrogen, which in turn is more expensive than the grey variety. Green hydrogen requires renewable energy and green hydrogen is just not a particularly efficient application of that energy as you need rather a lot of it.
A kilo of hydrogen is the equivalent of about 33 kwh. The market price of hydrogen varies wildly depending on how it is produced, transported and stored. The green variety is about 7$ per kilo. Or about 21 cents per kwh. Grey hydrogen (the dirty stuff) is about a dollar in the best cases. That's still about 3 cents per kwh. Grid prices for renewables vary widely but in the areas most likely to get involved with green hydrogen (i.e. middle east) they are between 1 and 2 cents per kwh for some recent renewable setups. So that's a factor of 3-21x depending on how you look at it. Blue hydrogen is somewhere in the bottom of that range.
That's not the hydrogen's fundamental fault as a medium. It's the fault of the conversion process. 33 kWh of thermal to 15 kWh of work, according to your calculation. That's in the realm of highly efficient (Diesel) internal combustion engines.
As for 4 miles per kWh for a Tesla, you're already comparing apples to oranges. The Tesla feeds off batteries, where the expensive conversion part is already past. You're comparing high-exergy (battery) to low-exergy (raw hydrogen).
I don't know anything about fuel cells, but imagine they reach 90% efficiency (is that even theoretically possible? Don't know); suddenly you get 30 kWh of work out of 1kg of hydrogen. We're just starting out, and a hundred years ago ICE efficiencies were atrocious, too.
And hydrogen is produced via electricity, so I’m not skewing the discussion at all.
Round trip efficiency of battery is 90-95% (can be higher). Round trip for hydrogen (ie electrolysis & then storage and then fuel cell conversion back to electricity), including cooling (required for fast refueling) and compression, is about 25-40%. Even when that hydrogen is already in your tank, you only get about 60% of the energy out of it in useful energy. Heck, in California, hydrogen stations typically are only 33% renewable with most of it being gray hydrogen (9.3kg of CO2 per kg of gray hydrogen, not counting liquefaction), which makes hydrogen cars even at $10-14/kg, worse for the environment than even just random electric cars (although many EVs use primarily nuclear or renewables).
And while electric cars can have distribution losses, they’re pretty low, ie single-digit percent. But hydrogen stations are almost always refueled by truck, which has its own inefficiencies, and the stations also must constantly maintain the hydrogen at cryogenic temperatures to be ready to fuel. Also, some new stations get fuel delivered as liquid hydrogen, which is denser than compressed and therefore easier to transport, but liquefying 1kg of hydrogen (and converting it to para-hydrogen, which is normal) requires about 10-13kWh of electricity… which could send a Model 3 about 40-50 miles. So you almost can get further on an electric car on just the energy needed to distribute the kilogram of hydrogen as the hydrogen car can get by consuming that kilogram!
It’s pretty bad. Hydrogen for transport just doesn’t make much sense except for niche use cases. Maybe the last 10% of air transport that proves electrification-resistant or certain long distance ships or rockets.
Are we just starting out with fuel cells? They were on the Apollo missions and the Space Shuttle, and Wikipedia says they were invented in 1838 and commercialised in 1932.
The 33kWh per kilo of hydrogen - that's the absolute physical limit of green hydrogen production via electrolysis, assuming 100% efficient production, no leaks, no labor, no maintenance, no electricity losses, frictionless transportation and infrastructure that just magically pops up where needed. It's not the case that technology will push the price down - this is the best anyone can ever hope for
That's just a physical material property of hydrogen itself. It has nothing at all to do with anything else. 1kg of hydrogen has a (lower, not upper) calorific value of about 33 kWh, period. Doesn't matter where it's going, how it was made, what infrastructure was used, what any of the efficiencies involved were, ... You could magically conjure up 1kg of hydrogen from outer space and it would have that property too.