Why not just make electric tractors? The energy efficiency of converting wind -> electricity -> fuel -> mechanical power has to be less efficient than wind -> electricity -> mechanical power right?
Tractors are very expensive. Farmers will not replace them just for this. And, they need to operate all day long, which would take a hell of a lot of battery.
Retrofitting with ammonia tankage and plumbing (making them cheaper to run) is an expense they might prefer to avoid until they have a reliable secondary supply of ammonia.
They need to run all day and all night for ~2 weeks straight twice a year and then they can sit idle most of the rest of the time. But during those 4 weeks charging for one out of every three hours (I’m assuming that a big tractor pulling a big implement is going to deplete even a really big battery fast and charging a battery that large is probably going to take a long time) isn’t going to be tolerable.
It is easier and cheaper to store liquid fuel. Making liquid fuel would allow fuel to be made and stored in the off season in a greater quantity than could be reasonable be stored in batteries.
> The energy efficiency of converting wind -> electricity -> fuel -> mechanical power has to be less efficient than wind -> electricity -> mechanical power
It depends on how efficient it is to use existing ICE tractors vs creating new electric tractors. If tractors are like other ICE vehicles then something like half the energy they take over their lifetime is used in their production so if you want to get to Net-0 sooner generating carbon neutral fuel might be the way to go.
Efficiency is secondary. Cost is primary. As the cost of generator capacity continues on down, people worry less about efficiency. The top-line input, sunshine, is free. So it is a question of capital cost amortized over energy produced.
While the question I was responding to was explicitly about efficiency, you might be right about cost. However, ICE tractors that are already owned along with the capital required for their use and maintenance are potentially a lot more attractive to keep vs new electric tractors. Sunshine might be free but it’s not available in sufficient quantities everywhere with current technology, and all technologies will require ongoing maintenance. With China becoming an untrustworthy trade partner the cost of solar panels will likely rise. If they do I hope they can make affordable efuel so that we make progress either way.
Solar panels are produced in many more places, now. (Former-Soviet) Georgia produces a very great number of them, for example, at exemplary prices.
There is plenty of sunshine most places if you can bank fuel during off-season. Finns will probably still need to import from the south or via transmission line if the wind is off -- as they have done for many decades on a more regular schedule.
You seem to be saying you think keeping liquid fuel in tanks does not qualify as storage. If that is what you mean, you will need to explain why you think that, because it makes no sense.
If you mean we have not yet built out as much storage as we will ultimately need, because we anyway haven't enough renewable generating capacity built out yet to charge it from, then yes we know. The solution to that is obviously to continue building out renewable generating capacity, and then storage for the excess.
> You seem to be saying you think keeping liquid fuel in tanks does not qualify as storage.
I just misread what you wrote. I didn't see "fuel" and thought you were referring to other means of renewable storage. Fuel as an efficient and much less geographically limited means of storage makes a lot of sense.
Chart omits liquified anhydrous ammonia. Its volumetric energy density is about half of diesel's, with a somewhat better mass energy density. You need bigger tanks that can hold back a bit of pressure, and new plumbing disinclined to corrosion.
It also omits liquified hydrogen, which is inconvenient to handle, but not much moreso than liquified methane.
With the amounts of extra weight farmers often add to their tractors, and their general hatred of DEF and regen cycles, electric tractors seem like a billion dollar idea just waiting for someone to pick it up and run with it.
I doubt batteries are up to the task. Tractors and implements are big, so the battery is going to have to be huge, which is going to further increase the weight of the tractor and so on. Plus if you’re in the middle of harvest season (you have a narrow window to get crops out of the ground and you work around the clock for a week or so), you can’t afford to wait an hour to charge your tractor after driving it for an hour or two. Anyway, you would have to have electricity in ample supply on site or else you’re taking your tractor offline for even longer while you drive it to and from your field for a charge.
Boutique item, maybe unless the batteries can be replaced while it operates. They would need a hell of a lot of spare batteries, and somebody running around replacing them. Presumably today people are driving out to fill up fuel in existing tractors after some number of rows.
Yes and no. It's not targeted at massive monoculture farms such as corn farms in the Midwest. Rather it is targeted at operations where a smaller tractor with a few hours runtime is useful. That includes not only hobby farmers but also vineyards, etc.
