this post was submitted on 11 Feb 2024
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Most if not all freight locomotives are diesel electric as well.
You’re just not going to beat the energy density of diesel. 1 gallon of diesel fuel has roughly 40kwh worth of energy in it. Modern diesel motors are around 35% efficient.
So you’re looking at ~14kwh of useable energy from 1 gallon of diesel, weighing 7 pounds. So 1kwh is around 0.5lbs.
1kwh of EV battery currently weighs ~13-14lbs based on the model 3s battery capacity and weight as well as the Hummer EV.
So on a train or truck with a 5,000gal tank (just using the AC600X locomotive as an example), you’re talking 35,000lbs of carried fuel and 70,000kWh of useable energy.
To carry the same energy, you would need 910,000-980,000lbs of batteries. Twice the weight of the locomotive itself. Even if we increase the density by a factor of 10, you still need almost 3x the weight of batteries as you do diesel.
And the time to charge a 70MWh battery would be insanely prohibitive. Like a few days each time. With a 1MW charger you’re looking at minimum 70 hours if you could run at peak power with no losses. Realistically more like 80 hours with how chargers slow down as the battery gets full and charging losses.
Natural gas could used to be a little bit cleaner, but CNG vehicles use 12-15% more fuel to get the same power than diesels so it would really be a wash on CO2 emissions. And you would have to replace every diesel engine out there along with all the infrastructure just for a less efficient power source. Natural gas is phenomenal for large scale power plants, not as much for ICE vehicles.
It’s the same issue with large ships. You just can’t beat the energy density of petroleum. And ships use the nastiest byproducts of oil refining already because they’re so cheap. Banning using bunker fuel would just cause them to switch to diesel for a little more rather than go full EV. Going back to sail boats is going to happen before EV boats lol.
Same with planes. Batteries are just too heavy for aircraft in any large capacity. Plus it’s not like we really want a bunch of giant flying lithium bombs overhead. Putting out an EV fire is already insanely difficult. Imagine trying to put out the fire from a battery 10x larger that crashed in the woods somewhere.
Diesel isn’t going anywhere any time soon. I would imagine we start producing more biodiesel before the really heavy machinery goes full electric. And as long as there is diesel in use, it’s gonna make its way to consumers in large pickups because diesel can’t just sit around forever and companies are gonna do whatever they can to keep production high to make money.
At least with the locomotive example, you could make it fully electric and hook it up to the grid vs trying to haul around the electricity itself. Would require a good amount of retrofitting to work with existing rail lines, but would be a hell of a lot easier than alternatives to get ICE out of railway power.
For a freight train you absolutely couldn’t. Even high power lines aren’t powerful enough to power the electric motors on a locomotive through the standard way that things like light rails operate.
That locomotive example I used has a 4.5MW electric motor output. It would be next to impossible to get 4.5MW from the line to the motor using a third rail or something. The power draw would be too great for a freight train with say 6 locomotives. I live 50 feet from a rail line and 6 locomotives is about the average I see per train.
And just for scale, there are over 26,000 Class I locomotives like that in service. If each one ran for only 12 hours per day on average, that would eat up half a trillion kWh of power per year. That would be 12% of the total US electricity production per year, assuming no losses in transmission or efficiency.
Most modern electric locos and EMUs are 6 MW and up on European 15 or 25 kV AC systems. 8-9 MW is very typical for higher end locos and the BR412 EMU in its longest configuration (for an example of the maximum I can think of) can pull 11.55 MW temporarily, and all of that is from one pantograph. Doing cargo with electric locos is only impossible in NA because... well, because you can't, because there is no elecrification. Every single corner to has been cut to save every imaginable cost. It's not like you could try and see what's better, you literally only have old-school diesel tech.