PV Trackers [RE-wrenches]

[Matt Tritt]

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  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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Archive of previous messages: http://lists.topica.com/lists/RE-wrenches/read

List rules & etiquette: www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/

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Moderator: michael.welch at homepower.com
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