Fixed vs. Tracking for Pumping (was:PV Trackers) [RE-wrenches]

[Windy Dankoff, Dankoff Solar]

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Matt,

With almost any solar pump system, you can go to 2X the required PV 
watts, or more, without problem. The pump system draws according to the 
load, and has overcurrent protection in case of overload.  What blows 
the controller is more likely to be excessive Voc, and that's not an 
issue if the array is wired for the right voltage.

Is array oversize an economical approach?
     In a cloudy climate for domestic water (needed every day) -- yes, 
potentially. Tracking won't help so much.
     In a dry sunny climate for agriculture (not needed much in cloudy 
weather) -- no. Tracker is more economical.
     With a very small PV array -- yes. Extra watts may cost less than a 
tracker
     Larger array -- no. Tracking is much cheaper than PV watts.

This is a theoretical discussion of course, not considering potential 
problems and preferences around the matter of trackers in the real 
world. I CAN say that there are lots of ranchers who use passive 
trackers with enthusiasm -- most often, the small and medium sizes.

Windy





On Sep 16, 2004, at 3:45 PM, Matt Tritt wrote:

>
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>
>   Well, I bet the problem I'm having convincing you how I'm right (LOL)
> about this is the kind of pumps you're working with. Or maybe not!
>
>   Here's the way I see it: A particular pump is designed to operate 
> withiin
> a particular, narrow window of efficiency to deliver a maximum 
> head/flow
> ratio. If this pump has a 1200 Watt motor let's say, you aren't going 
> to be
> able to give it MORE than it is capable of using without damaging the 
> pump,
> damaging the controller, voiding the warranty or blowing off the extra 
> Watts
> as waste heat, even though a certain amount of extra run time can be
> achieved. Maybe.
>
>   If you use a tracker you can fit the array output to the pump motor
> exactly AND have maximum output during the entire day - month - year; 
> plus
> you keep the warranty and the machinery in tact. Using a good tracker 
> (and
> why shouldn't one last 30 years?) shouldn't worry you at all; yes 
> there may
> be moving parts to watch, but so what?
>
>   I think that it's perfectly logical and acceptable to charge for 
> repairs
> and maintenance of any machinery/equipment after the warranty is over. 
> All
> equipment made is subject to wear and tear and maintenance, right? So 
> why
> should a tracker be any different? O.K. the older Wattsuns can run you
> ragged chaning motors, photo eyes and controllers. True, true, true. 
> And
> yes, they all began failing within an unacceptably short period of
> time.........That's why it's so terribly important to periodically 
> purge
> your memory cells and start over!
>
>   Matt T
>
>
>   ----- Original Message -----
>   From: "Travis Creswell, Ozark Solar" <ozsolar at ipa.net>
>   To: <RE-wrenches at topica.com>missionData
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>   Hi Matt,
>
>
>
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