Re: Grid-Battery "Hybrid" Tractors



batteries (Zebra's, sodium/sulfur etc) are excellent :

Energy density ? 150 Wh/kg has been reported. Similar to Li-poly. Even higher for NaS.
Cost ? That's a bit tricky. Currently only one factory in the world produces these batteries.
But I'm looking into this. Remember that this whole large battery business is in it's infancy.
Rob
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Rob Dekker wrote:

The site give the specs for a Zebra battery at 90 Wh/kg. The 300 kWh tractor used as an example in the thread would require well over 7000 pounds of those batteries, which would occupy over 78 cubic feet. That volume computation is based on the example given of a 195 kg Zebra at .13 cubic meter. See http://www.rolls-royce.com/marine/downloads/submarine/zebra_fact.pdf
The battery operating temperature is 250 C and must be kept under charge when not in use to keep the temperature there. If you allow it to cool, it can take up to 2 days to get it up to temperature again before you can use it.
The farmer who has a tractor powered by this type of battery is going to have one helluva job removing 7333 pounds of batteries and hauling that to the recycler, and another helluva job of installing the 7000 plus pounds of replacement batteries.
I did not find recharge time, but it will certainly cut into the farmer's productivity, as compared to diesel.
Based on what is posted on the Wiki site and the thread here, the idea that this technology, as it is today, can be a practical alternative to diesel in tractors is totally ludicrous. And that is without considering the purchase price of the batteries and charging equipment, or the cost of installing the charging equipment.
Ed
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ehsjr wrote:

See what happens following Bret's threads......?
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READ THIS:

_What_ example?
_My_ example was for the tractor crossing the field in the typical 6 - 10 minutes. (See above.) The 6 - 10 mph typical tractor speed figure has been confirmed by other posters citing government and industry web sites.
A 400 hp tractor running wide open moving at 0.5 mph would require several months to work one square mile and, in 6 years, at the present rate of spiraling fuel costs, run up a debt of a half a million dollars just for the diesel.
The 0.5 mph strawman was generated by a useful idiot who unwittingly helped me build the case for grid-battery.

Almost all field operations allow the tractor to recharge every 6 - 10 minutes requiring only 10 - 30 kW hrs/charge.
30 kW-hr/(0.09 kW-hr/kg) = 733 lbs. The overall drive train will be lighter than the diesel + fuel tank.
I've mentioned this several times and everyone dodges this issue:
Grid battery farm electrification is possible with low density energy storge devices, an advantage not shared by road hybrids or EVs.
Any argument for EVs or hybrid electric is, a fortiori, an argument for grid-battery tractors.
And, _no_ pausing at the end of the field to recharge is _not_ a big issue.
Right now farmers are paying truck drivers $100/trip to run 8 peso/ litre diesel from Mexico at a savings of only 40% over U. S. prices. This ties up truck and driver time.
Instead of paying a truck driver to sit in line at the border why not pay a tractor driver to sit at the end of the field?
At least you don't getting pestered by customs agents and junk food peddlers sitting out at the edge of a field.
The hay guys seem to move fast -- they get across the field in 2 minutes -- but the rest spend 15 minutes each lap screwing around at the end of the field lining up their lasers or whatever anyway.
Bret Cahill

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snipped-for-privacy@peoplepc.com wrote:

You have to be kidding. Do you think farmers work almost every waking moment during planting season because they like the hours? Patience is in short supply during the spring. Any delay due to breakdowns and such drives them nuts. The goal is to keep the planters moving until the job is done. Planting season starts around April 10 or so in my area of Nebraska. Things generally get wrapped up by the second or third week in May.
Dean
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Electric motors are more reliable than diesel.

The field needs to be automated so that the machinery runs 24/7 with lasers and GPS. Just put in the crop's CD and the coordinates of the field.

For places with only one or 2 seasons, time is less critical.
When the price of diesel gets high enough it'll be cheaper to run 2 electric tractors and pay two drivers than one diesel.
Bret Cahill
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Instead of one 700 lb battery that stays in the tractor, two 350 lb batteries would be cantilevered off both sides of the tractor with a wire on both ends of the field. The batteries have a verticle rod mounted on top to contact the wire.
When the tractor reaches the right hand U turn end of the field the left outrigger scoops up a recharged battery. After the U turn the discharged battery is dropped off for charging and can be picked up on the next lap.
The right side battery is swapped out at the other end of the field when the left hand U turn is made.
The batteries only last a few weeks and are changed - recycled like motor oil.
Battery cost is about twice grid cost -- the combination is just now about equal to the cost of diesel -- so in the long run it might be cheaper to trolly wire the entire field or go with the super pivot.
There are all kinds of farm situations and there will be all kinds of solutions.
The original single battery single wire idea where the driver waits at the end of the field for a recharge was the absolute cheapest easiest electric tractor to prototype and demonstrate. It was just a way to get a foot into the extension center door.
Bret Cahill
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Sorry for the mis-quote. I DID find a manufacturers folder that reports 119 kWh/kg (better than NiMH) :
http://donau.kicms.de/cebi/easyCMS/FileManager/Files/MES-DEA/batteries/Zebra_Z5.pdf
MES DEA is constantly improving their batteries, and they are still quite far from the theoretical limit, so we should see higher numbers in the future. Thanks for the correction
..

I agree. Although ludicrous is a big word, 'currently unrealistic' is certainly applicable.
Batteries are nice for small tractors for lawnmowers etc (replacing noisy, inefficient 2-tact motors), but not for 400 hp diesel workhorses in the big fields.
Electric drive (like the Caterpillar tractor mentioned earlier) make much more sense currently for efficiency and torque improvements on big-ass farm equipment.
Rob
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Energy density just isn't a factor when you can recharge or swap out batteries several times/hr.
. . .

We really need a tractor pull to show a 350 lb battery just isn't a big deal.
Barring some breakthroughs in algae, diesel will soon be prohibitively expensive, with _any_ kind of drive. Why risk the food supply when there is such an effort to go EV or plug in anyway?
The EV and plug in industry will require much more metal and other materials for their batteries than agriculture will ever use.
And if battery costs don't drop very much, then there's always straight grid, either a lot of trolly wires or something based on a pivot irrigation system.
Bret Cahill
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snipped-for-privacy@peoplepc.com wrote:

It is not 350 pounds. Using the numbers posted in the thread (300kWh equivalent tractor, 90Wh/kg battery) it is over *7333* pounds of batteries. Energy density most certainly is a huge factor, if those numbers you & Rob have been posting are accurate.
A 350 pound Zebra battery would yield 14318 Wh. That is the equivalent of 19 horsepower - way too small for a tractor on a farm.
Ed

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It's more like 300 lbs max.

What part of "frequent recharge" do you NOT unnerstand?
A 400 hp tractor only needs a couple of gallons to get across a field.

Not that it matters but now he's saying 120 w- hr / kg.

For _what _ operation?

What part of "frequent recharge" do you NOT unnerstand?

Now everyone knows yer an idiot. Energy ain't power.
Bret Cahill
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It's more like 300 lbs max.

What part of "frequent recharge" do you NOT unnerstand?
A 400 hp tractor only needs a couple of gallons to get across a field.

Not that it matters but now he's saying 120 w- hr / kg.

For _what _ operation?

What part of "frequent recharge" do you NOT unnerstand?

Now everyone knows yer an idiot. Energy ain't power.
Bret Cahill
--
Hi Bret, Rob here.

I do not want to throw a monkey-wrench in the idea of plug-in tractors (I still
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SINCE ENERGY DENSITY ISN'T SUCH A BIG DEAL, WHAT ABOUT CAPS?
Sorry, no pun intended. My keyboard made an honest mistake.
Anyway, this would need to be spread sheeted to optimize and to determine competitiveness but several wires over the field could recharge multi farad capacitors in seconds.
Sure the caps would weigh more than batteries but they'ld last forever . . .
Bret Cahill
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Pity about the cost of all that wiring and the caps.
Biodiesel makes a hell of a lot more sense.

Nope, they dont.
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On Thu, 7 Aug 2008 21:32:14 -0700 (PDT), Bret Cahill

--
"Spread sheeted?"

LOL, you wouldn't even know what to enter into the various cells and
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Rob Dekker wrote:

What part of "equivalent tractor" do you NOT understand? While the battery powered tractor is re-charging, the diesel is still plowing. Equivalency is lost.
Ed
<snip>
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The part where it makes sense to pay $12/gallon for diesel.
Next question?
Bret Cahill
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On Sun, 10 Aug 2008 20:45:21 -0700 (PDT), snipped-for-privacy@peoplepc.com wrote:

--
What makes you take criticism so badly when you know you're wrong?

JF

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Here, I'll try again:
How does this change the cost/number of cycles?

How does this change the cost/number of cycles?

And?
Again, why wouldn't this also apply to series hybrids like the Volt?
Bret Cahill
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Bret Cahill wrote:

Because the tremendous cost of the batteries must be factored into the cost. I have two dead batteries for my ThinkPad laptop, because I bought a spare for nearly $100. This laptop has not used anywhere near $100 worth of electricity, and the batteries didn't last long at all.

Because unlike a car, you are beating on the batteries at a far higher rate -- about two orders of magnitude higher. What is barely feasible for a car is obviously unfeasible for a tractor.

So instead of burning through a set of batteries in two weeks, it could be one week or less than one week. The cost of batteries would greatly exceed the cost of the vehicle or the cost of electricity. If the other killer arguments against your proposal were not sufficient, this one by itself is sufficient.

It does, but on a time-scale that is two orders of magnitude longer. Farmers aren't going to be spending tens of thousands of dollars every one or two weeks to replace batteries. Your proposal is an obvious non-starter. Calling people morons who point this out to you does not increase your credibility.
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