PV Trackers [RE-wrenches]

[Ray Walters]

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I must agree with Matt. I have had the same experiences with wrong 
hardware, DOA trackers, flaking off paint, holes in the wrong places, etc. 
Then the factory gives you the "what's your problem, you whiner" customer 
service.  And I helped install the Trackers on the cover of their brochure. 
I work with everyone until they burn me enough times. I'd still work with 
them, but why?  Array' Technologies have the best service in the solar 
business. (which is tough to do considering how nice all you other folks 
out there are too)
We were so frustrated with Zomeworks, I got a MIG welder, machine tools, 
etc to make our own  fixed racks. Can't complain then.

Ray

>   Hi Windy,
>
>   We had a DOA tracker (we didn't know it before installation!) from ZW that
>took a crew of 8 guys to carry up the side of a brush covered, poison oak
>infested hill side punctuated with cholla cactus and rattlers. After the
>feat of getting it to the pole ,one of four, and assembling the bloody
>thing, we discovered that it just sat there.
>
>   This was the original pre-welded variety with the tube protected, so it
>wasn't a problem with handling damage. Since we had to go through the entire
>procedure again to get the thing down off the hill, cart it off to the
>trucking company and repeat the process with the replacement (that worked) I
>developed a permanent attitude I guess. Nothing like losing a bunch of time
>and money to educate you.
>
>   We also had numerous cases of Zomeworks equipment being un-crated in the
>field absent pieces and/or missing fasteners, or more fun, mixed SAE and
>metric fasteners. This sucks when it's a two hour (or more) drive to the
>nearest hardware store!
>
>   Jeff O. also brought up the issue of life expectancy of trackers as a
>deterrent for their use and the current tendency of many wrenches to
>substitute more panels to make up the difference.
>
>   Where I can see this as somewhat correct in larger grid-tied systems
>considering the rebate mechanism in California, the use of a tracker for
>pumping water is far better because of the very nature of solar powered
>pumps. You can't simply jam more water through a pump than it's designed to
>pump; the power must be supplied at a particular rate to match the pumps
>perfomance curve. In my experience, the only way to adequately pump with
>solar is to provide the right power over the longest period of daylight
>possible. That means a tracker.
>
>   So there.
>
>   Matt T
>   ----- Original Message -----
>   From: "Windy Dankoff, Dankoff Solar" <windy at dankoffsolar.com>
>   To: <RE-wrenches at topica.com>
>   Sent: Thursday, September 16, 2004 10:30 AM
>   Subject: Re: PV Trackers [RE-wrenches]
>
>
>
>
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>
>   Wrenches,
>
>   Nobody has mentioned seasonal-load pattern as a criteria for the choice
>   to use tracking. Passive trackers have always been popular for solar
>   pumps for agricultural applications where the most energy is needed in
>   clear summer weather. That's precisely when tracking gives the most
>   gain and has (with passive) the least problem with performance. It also
>   helps prevent pump stall at the early and late times of the day.
>
>   I would immediately advise against it for high-winter load and
>   predominantly cloudy / hazy climates, or sites that have the solar arc
>   restricted by shadows early or late in day.
>
>   Some swear by and some swear at passive trackers, but durability
>   doesn't seem to be such an issue. We've soldZomeworks trackers since
>   1981 and I've rarely seen failures (leaks) -- never any that are
>   structural and endanger the array as far as I know. They can always use
>   more refinement to work more consistently however. I have one at home.
>   It wakes up and tracks very consistently, even in turbulent wind and
>   cold, but never swings the full arc.
>
>   Windy
>
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Ray Walters
ray at solarray.com
President, SolarRay, Inc.
NABCEP Certified Solar PV Installer
BS Mechanical Engineering, UT Austin 88
Returned US Peace Corps Volunteer 

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