Center Pivot powered by renewables

[adobejoe]

We have a six span center pivot currently driven by a diesel engine. It uses a mechanicial take off to a hydraulic pump and 14 hydraulic motors on wheels to rotate the sprinkler. Figure we need about 10-15 HP 48 V, DC motor to drive hydraulic pump. System will operate at night: 12 hours on 12 hours off (day). Figure we need about 3,100 Amp Hours to drive the system.

So, we are looking at three strings of 2 V cells, or 72 batteries. 2 KW solar PV, and a 7.5 KW wind turbine. The system is going to need PLC control, and we would like the option to drive system if the batteries are charged and to use the "dump."  Comments welcome...is this doable?

Adobe Joe in the WINDY state of WYOMING

[scottsAI]

Adobejoe,

Your numbers look good for the battery.

The RE part of 2kw and 7.5kw is questionable.

Battery Power needs 12hp (mid range number) * 749 * 12hr = 107kwhr.

Motors are rarely 100% so adjust by its efficiency.

Battery efficiency must be added on.

If 7.5kw all day is real, your good to go for charging the battery.

I question if any location will produce full power winds all day long?

Not sure the purpose of the solar, depending on location 2kw * 9 hr = 18kwhr produces 1/6 of your power needs, little enough is it worth adding?

Every energy exchange looses power.

Wind/solar to battery to motor to hydraulic to motor is going to require more power than

14 small electric motors driven off the battery.

Not sure how the motors are controlled each will be driven at a different speed.

Not sure what you mean by:

we would like the option to drive system if the batteries are charged and to use the "dump."

Have fun,

Scottt.

[Airstream]

The poster needs hydraulics with no copper to steal & no line losses of 600' or more multiple wire runs.

I want to comment w/ suggestions but this is so interconnected no one 'module' stands alone.

Would looking into a 240VAC or even 3-phase battery fed inverter system to provide digital controllers industry standard power be justified?

[scottsAI]

Thanks Airstream, for verifying the system.

Took some digging to find a claim by Valley Technology: electric motors use 75% less power than Hydraulic. Of course they sell conversion kits!

Did not find yearly energy cost broken down by movement motors or well pump.

The center pivot irrigation design has many different solutions.

Suggestion: place a battery on the various wheel platforms, get rid of the high power wiring.

Largest battery goes on the outer section reducing size going towards center.

Since not studied this in much detail, did realize the battery is equal to 110 golf cart batteries, $7,700 battery! The weight of the water pipe will dwarf the weight of the battery.

Flooded batteries are cheaper, since remote, want auto battery watering system.

Wireless communications to the sections.

GPS to keep it aligned. Differential GPS keeps things within couple feet placement.

Solar and wind generators on the towers!!

Telescoping water pipe sizes.

Comment on wind turbines, One large unit is cheaper/watt than bunch of smaller units.

The better system is emotional as is the type of system.

So with that said. Later!

Thanks, was interesting looking at this system. Wondered about it before, now I know a little.

Have fun,

Scott.

[plainsman]

That is certainly a laudible goal. As a retired farmer who had many Valley sprinklers including a 20 tower and a 23 tower(driven by a 25 kw 3 phase   gen. belt driven by the center well motor. ) , and as  someone who now lives off grid, I thought I would throw in my two-cents worth....  I live in the very windy Oklahoma panhandle.  My wind turbine experience  has taught me to be assured of long term averages, but  to never expect  wind on the day you need it most! Do not depend on manufacturers ratings of wind turbines... they are over-inflated as an industry rule.  Do not expect to use your entire battery bank amp hour  ratings and expect them to last.... Read their info... life expectancy ratings are based  on only half dischsrge.... Check out cheapsolar.com for large quantities of the best value in pv. they don't sell panels, they do a daily price report of the lowest prices.  I haven't run the numbers, but I would give an off-hand estimate of 20k$+ for your   project  to work reasonably well (renewable energy has a way of always costing you far more than you plan)  One other option would be to start building some otherpower 10' machines then work up to the 17' one.  I just built a 10', saved a lot and it works well!  Good luck! and keep us posted on  your progress!

[ghurd]

That link you gave is yet another sort of deceitful cover site for "Parts On Sale".

Which I hope is not the link you meant.

G-

[adobejoe]

Thanks for your comments. We are located in NW Wyoming and have very good wind, although of course July and August (when we need the water most) is less windy. The hydraulic system uses poppit type valves to keep the whole system aligned. We will probably up the PV to 4 KW capacity. System needs to be outside the circle, and will also power a house in the winter months.

Adobe Joe

[Airstream]

After sleeping on proposal of 'irrigation on renewables' overnight, to stay with renewables AND to get the 100% on-time service required I believe having an oil seed crop such as sunflower or rapeseed(or... other?) a silo & rotary oil press to power a diesel system capable of long term maintenance of the system with using Solar and wind to reduce the diesel run times, power the drying and extraction, etc.

Lightning, wind and hail, theft etc. could shut down a PV system beyond quick repair and a whole crop rotation would be jeopardized...

[plainsman]

I didnt know that, thought it was just a solar panel price review. sorry bout that

[ghurd]

There is a honest review with a name something close to that,

but I'll be darned if I can find it again.

G-

[DanG]

http://www.ecobusinesslinks.com/solar_panels.htm

[anteror]

Use cheap windpower;

http://www.thebackshed.com/windmill/forum1/forum_posts.asp?TID=2034&PN=1

Antero

Finland

[ZamPepper]

Agriculture Solar says that they have completely offset the energy usage with their center pivot system:

http://agriculturesolar.com/3b_center_pivot_irrigation_solar_powered.html