5 ms·

Temper tantrums are fun. I get it. It's better to use numbers though. Diesel produces roughly 37 kwh/gallon [1] a powerwall can supply about 12kwh "all day" [2]

by jfoutz 10y ago

Temper tantrums are fun. I get it. It's better to use numbers though. Diesel produces roughly 37 kwh/gallon [1] a powerwall can supply about 12kwh "all day" [2]. A powerpack is more like 100kwh. So, let's say 10 gallons an hour. you'd need 30 powerwall 2s to cover power needs. I think you're underestimating how well electric motors do in low speed high torque situations. I'd bet there are some efficiencies to be gained from those characteristics. Simpler mechanical linkages. One motor per application rather than a big hydraulic system and a funny transmission, for example. On the down side, batteries are HEAVY. You probably lose most of the weight savings from simplification to added mass in batteries. Back on the pro side, simpler systems are simpler to repair and maintain. But, i get your point, it's probably not there yet. [1] https://en.wikipedia.org/wiki/Gasoline_gallon_equivalent https://en.wikipedia.org/wiki/Gasoline_gallon_equivalent [2] https://en.wikipedia.org/wiki/Tesla_Powerwall https://en.wikipedia.org/wiki/Tesla_Powerwall

hueving 10y ago
10 gal an hour is too low. I know someone who does soybeans at about 20 gallons per hour. So 60 powerwall 2s. Even if you solve the weight issue (60*270 lbs = 16,000 Lbs), the $330,000 cost for that many packs every 10 years makes it infeasible. That doesnt even account for electricity cost.
- jfoutz 10y ago
  Poking around a little it looks like the real measures are gallons per acre. Which makes sense, a gigantic machine moving fast will clear a ton of acreage, and suck down fuel like it's going out of style. So i picked a bad measure. As i said, i mostly agree, it's just not there today. That said, battery capacity historically improves 5-8% a year. Cars aren't worth it, but they're very close. I'd take the yes side of a $10 bet about John Deere selling an electric tractor in 15 years or less.
  - emp_zealoth 10y ago
    Sure, maybe a tiny utility one. Actual workhorse? Those can have 200L or 400L or even bigger tanks - when you go out in the field you are going to stay there until the work is done (or the day is done). So account for 10 or 12 or more hours of work. So let's take the best case scenario - 200L tank on a machine that takes ~10 gallons (say 50L) 40% efficiency for the diesel engine cuts energy available from the tank giving us 3040kWh for 4 hours of work of not-the-biggest machine That is ~225 powerWALLS (at 5,500$ a pop it gives us 1,237,500$), The weight is 27000 kg That is 16 powerPACKS 2 (wiki doesn't say if those are available really) - at 145,100$ a pop it comes out to 2,321,600 - but it might be wiki numbers, it also says 445$/kWh - it comes out to 1,352,800$ - more reasonable compared to powerwalls, the weight is ~26000kg That is for a small-ish (relatively) machine with 200L tank, for 4h of work... Now take a 20 gallon/h that works for 10 hours. And finally, we come to the issue of lifespan. In work machines you are going to be using close to nominal power for the whole time it's working - batteries don't like that, they get hot, the cells might die and worst of all it really damages even the working ones Then there is an issue of ground pressure - you don't want your machine sinking into the ground and fucking it up
jacquesm 10y ago
You'd still use the hydraulics, they are by far the best solution for that application. Utterly reliable, extremely high power levels available if required, no gears or other fragile bits. The most likely way in which that would work would be an electrically driven hydraulic compressor and the rest of the system stays just the way it is today. A large farm tractor produces 100KW to 200KW of power, and most of that in high torque low RPM situations where an electric motor would definitely be a contender (that's why we have diesel-electric hybrid locomotives as well). A simpler drive train would also be a big gain for maintenance reasons, the weight added by the batteries would not be a huge issue, weight in a tractor isn't nearly as bad as in a regular road vehicle, in fact for many tractor applications weight is added to the machine on purpose.

by jfoutz 10y ago

hueving 10y ago

10 gal an hour is too low. I know someone who does soybeans at about 20 gallons per hour. So 60 powerwall 2s. Even if you solve the weight issue (60*270 lbs = 16,000 Lbs), the $330,000 cost for that many packs every 10 years makes it infeasible. That doesnt even account for electricity cost.

jfoutz 10y ago
Poking around a little it looks like the real measures are gallons per acre. Which makes sense, a gigantic machine moving fast will clear a ton of acreage, and suck down fuel like it's going out of style. So i picked a bad measure. As i said, i mostly agree, it's just not there today. That said, battery capacity historically improves 5-8% a year. Cars aren't worth it, but they're very close. I'd take the yes side of a $10 bet about John Deere selling an electric tractor in 15 years or less.
- emp_zealoth 10y ago
  Sure, maybe a tiny utility one. Actual workhorse? Those can have 200L or 400L or even bigger tanks - when you go out in the field you are going to stay there until the work is done (or the day is done). So account for 10 or 12 or more hours of work. So let's take the best case scenario - 200L tank on a machine that takes ~10 gallons (say 50L) 40% efficiency for the diesel engine cuts energy available from the tank giving us 3040kWh for 4 hours of work of not-the-biggest machine That is ~225 powerWALLS (at 5,500$ a pop it gives us 1,237,500$), The weight is 27000 kg That is 16 powerPACKS 2 (wiki doesn't say if those are available really) - at 145,100$ a pop it comes out to 2,321,600 - but it might be wiki numbers, it also says 445$/kWh - it comes out to 1,352,800$ - more reasonable compared to powerwalls, the weight is ~26000kg That is for a small-ish (relatively) machine with 200L tank, for 4h of work... Now take a 20 gallon/h that works for 10 hours. And finally, we come to the issue of lifespan. In work machines you are going to be using close to nominal power for the whole time it's working - batteries don't like that, they get hot, the cells might die and worst of all it really damages even the working ones Then there is an issue of ground pressure - you don't want your machine sinking into the ground and fucking it up

jacquesm 10y ago

You'd still use the hydraulics, they are by far the best solution for that application. Utterly reliable, extremely high power levels available if required, no gears or other fragile bits. The most likely way in which that would work would be an electrically driven hydraulic compressor and the rest of the system stays just the way it is today. A large farm tractor produces 100KW to 200KW of power, and most of that in high torque low RPM situations where an electric motor would definitely be a contender (that's why we have diesel-electric hybrid locomotives as well). A simpler drive train would also be a big gain for maintenance reasons, the weight added by the batteries would not be a huge issue, weight in a tractor isn't nearly as bad as in a regular road vehicle, in fact for many tractor applications weight is added to the machine on purpose.