this post was submitted on 29 Sep 2024
72 points (97.4% liked)
Solarpunk technology
2367 readers
1 users here now
Technology for a Solar-Punk future.
Airships and hydroponic farms...
founded 2 years ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
A 240 tonne battery? That's almost 240 tonnes less payload. They should make one that runs on hydrogen or ammonia.
No the truck is 240T I think
Ah you're right. Assuming an energy density of 160 Wh/kg that's still almost 12,000kg. That much hydrogen contains about 400MWh.
The theoretical energy density assumes no cryogenic tanks, no plumbing, and no fuel cells. Also the production, storage, and transfer of Hydrogen as a fuel is INCREDIBLY inefficient.
Okay, but this application only requires 1.9MWh on board. That would be about 57kg of hydrogen. The required capacity would actually be less since the hydrogen refuel time should be significantly less than recharging a battery. Anyway, I just doubt very much that 11,900kg storage vessels and fuel cell would be required. There's simply less dead weight in a hydrogen vehicle as well as better performance and less externalities associated with battery production and disposal/recycling.
As for the efficiency of hydrogen production and delivery, it shouldn't matter. We need to produce it anyway for emissions free steel and fertilizer production. The real problem is that we don't have enough emissions free energy production, which isn't one that battery vehicles or storage facilities solve. The current paradigm is one of deficit in order to create a market and I think battery storage unfortunately facilitates that. Instead, we need to build out capacity so that there's almost always a surplus of electricity with the extra getting diverted to hydrogen production. It should be rare that the process is reversed to turn hydrogen back into electricity for the grid. That hydrogen is currently too expensive is the result of bad policy, which BEVs just reinforce.
Then your looking at almost an order of magnitude increase in fuel costs and a related increase in operating costs rather than savings.
Why would the operating costs be higher?
Because green hydrogen is expensive, and the more realistic projections estimate it will remain so to at least 2050.
If we use the CRU estimations, which notably are a trade group very much betting on green hydrogen adoption, we should be expecting at best a price of $3 dollars a kg in the distant future, with the current best price being more in the range of $6-$7 dollars a kg. With a 65% effective fuel cell that works out to the hauler getting its electricity at 28 cents a kwh with the possibility of going down to as low as 14 cents a kwh in future.
For reference, the average industrial electricity rate in 2023 was 8 cents per kwh, and Lazard puts the cost of utility scale solar at between 3 and 9 cents a kwh if a mine wants to roll their own. Wholesale Diesel fuel has ranged from about $2 to about $2.8 a gallon so at a reasonable 38% efficiency you get about 14 to 20 cents per kwh.
Not as bad as I expected offhand thanks to the current low cost of industrial green hydrogen, but your still looking at spending a massive amount of money for big platinum catalyst fuel cells and electric powertrains all so that you can spend thirty percent more on fuel than you do currently, as compared to using the grid directly for fifty percent less than you currently spend.
And we haven’t even mentioned that these things are going up and down a steep grade all day, so not only do you want massive batteries anyway so you can recharge on the way down, but you need them because unlike a small FCEV where it’s fuel cell is nowhere near large enough to output full power (and as such is only used to charge the battery) you do actually need to be able to sustain full power for the whole trip up.
TLDR: Industrial electricity is far cheaper than Diesel, let alone the more expensive green hydrogen. Hydrogen may be able to compete on a one or one level with Diesel in the far future, but given the upfront cost of the kit you might as well go all the way so you’re saving money over the long term.
I meant apart from the hydrogen fuel costs. It's not obvious to me why the labor and maintenance costs of hydrogen powered mining vehicles wouldn't be greater than that of the battery powered versions and the attendant charging/battery swapping equipment.
Mostly its the fuel costs adding to operating costs, but dealing with a cryogenic and highly flammable liquid/gas and all the related fluid handling, pressure regulators, and piping necessary is always going to be more labor and repair intensive than just expanding and directly charging the battery the vehicle needs to have anyway.