GRA said:
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See suggestion above about contacting the companies making battery packs or fuel cell stacks for buses. 225 kW is probably about the right range for them, not that I'm suggesting either for the reasons already given. As to bio-diesel, net-zero carbon bio-diesel should be findable, but emissions-free, no, although most emissions other than NOx will decrease - see http://www.afdc.energy.gov/vehicles/diesels_emissions.html. However, ii should be a drop-in for the tractor, if they're using diesel now.
I'm not doing a hybrid or other compromise for expediency.
There are lots of places to make battery packs... that's really easy.
There aren't many H2 stacks that are both compact and capable of 225kW. Without a doubt, the hydrogen method might be orders of magnitude more expensive with one gain: fast refueling.
Main drawbacks of a H2 -vs- EV farm tractor:
1) no available infrastructure -vs- "ubiquitous" electricity right on the farm
2) hardware cost
3) "rare" H2 equipment -vs- somewhat easy to get EV stuff
4) while an H2 setup is likely significantly lighter, the tractor can easily handle the weight (farmers typically add "ballast" in the tires and on the tractor)... weight helps traction.