>> re cables to power electric tractors...
>> see �"center pivot irrigation"
>> If they can do this, they can figure out how to get a cable to a
>> tractor.
> � � � There's a world of difference in the power requirements. �
The real concern is how to manage the cable. The appeal of straight
grid is undeniable: Grid is only _one fourth_ the cost of diesel and
"dropping."
Grid-battery is now about 3/4ths the cost of diesel but it's dropping
just as fast.
On the other hand, while farmers are pretty good at dealing with Rube
Goldberg contraptions -- some of the impliments need to be in horror
movies -- I look at a field and think, "no way I'm gonna pry a farmer
from his water wars to adopt Etch O Sketch kinematics."
> Center
> pivot motors are three phase 480 in the U.S. �The older ones used either
> a single one horsepower motor or a horse and a half motor. �The newer
> ones use motors half that size. �The older ones had 10 AWG Cu in the
> span cable to power the pivots that were 1/4 mile long. �The newer ones
> can get by with 12 AWG Cu to power the motors.
A heavier gauge cable isn't going to crush the pivot.
> � � �Tractors in my area are probably in the range of 150 to 200
> horsepower or so. �Front wheel assist with duals rather than the four
> wheelers Brett talks about.
> � � �Take a 100 horsepower irrigation well motor with a pivot. �A
> quarter mile run from the power supply to the center point where the
> well might be. �That would take 250 or 350 MCM aluminum wire depending
> on the voltage drop one wants.
They still use diesel irrigation pumps here. A crop insurance
adjuster assures me that they use diesel pumps in Florida as well.
Saturday I was out cycling and passed a field irrigated with miles of
aluminum pipe and a gazillion sprinklers being pumped by a diesel 30
feet from a power line.
Now _that_ would be easy.
> � � You'd have to double the distance and double the amperage to make a
> 200 horsepower tractor run at the far end of the pivot.
OK.
> � � �Then there would be the problem of getting the power to the fields
> in the first place. �Power companies probably wouldn't be all that eager
> to put up lines that would be needed only part of the time.
I can't even get UP to save $2.5 billion a year in diesel by
electrifying their main line in the desert.
Railroads are a much more obvious candidate than farms.
> � � Most of the irrigation wells in my area are on interruptible power.
> � �The suppliers can shut them off by remote control if the load gets
> too heavy from other uses. �Thats fine for irrigation but probably not
> for field operations that need to get done in a timely manner.
Place Sandia dishes or PV in the "corners" clipped off by the circular
field.
Bret Cahill
