[RE-wrenches] Evergreen

Sun Jan 3 12:17:57 PST 2010

David is correct. The economics use to be in favor of trackers but not anymore. I use to sell a lot of 8-module Zomeworks trackers to people who liked gadgets, bought 4 or 6 modules, planned to add more modules later, and had a place for a pole mounted array. A tracker can still make economic sense if more energy is needed in summer (water pumping, fan, a/c, etc.), but there is no wisdom in adding moving parts to a PV system. Still, some people like the sci-fi retro-modern look of trackers.
Joel Davidson
  ----- Original Message ----- 
  From: David Katz 
  To: RE-wrenches 
  Sent: Sunday, January 03, 2010 11:35 AM
  Subject: Re: [RE-wrenches] Evergreen

  Since modules are getting so inexpensive, the big questions is what is the best way to get 33% more power? Is it better to use 33% more modules on a fixed array, or use a tracker?  Which one costs less?  It costs $1.50 to $2.00 per watt for a tracker.   If modules cost $3 per watt and a fixed mount costs $.040 per watt , 33% of $3.40 per watt is $1.12 per watt.   And trackers don't come with a 25 year power output warranty.  I see tackers making sense when the array is powering a centrifugal pump in the summer or possible a time-of-use grid tie that pays more in the summer.  You are definitely better off with more modules on a fixed array in an off grid situation because you always need more power in the winter when the tracker is least effective.
  David

  David Katz

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  AEE Solar

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  Dana wrote: 
    You got it!

    It boggles my mind to watch the two OB FM60s and see the difference each day and then to go back and see the data over time. It is a very good argument for tracking. We have a Durango client that we installed 12 KW GIT tracked and it is outperforming the expectations of our client too.

    Dana Orzel

    Great Solar Works, Inc

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    I will be the shift in how the world uses power! - Dana Orzel

    From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Allan Sindelar
    Sent: Thursday, December 31, 2009 8:13 PM
    To: RE-wrenches
    Subject: Re: [RE-wrenches] Evergreen

    Dana,
    Thank you for this information. I would like to clarify what you wrote. We have long accepted that trackers may be expected to increase daily output by about 35-40% in the summer and 10-15% in the winter, due to the differences in the sun's seasonal elevation and the resultant length of the solar day. It sounds as if you measured the effective increase from approximately summer solstice - winter solstice and got a 32% gain. You previously got the same gain (33%) measuring from last winter solstice to summer solstice. This makes sense, as it averages winter and summer gains over two roughly equal periods, with variations (summer monsoons, etc.) being within acceptable error. 
    And whether grid-tied, grid-tied with backup, or off-grid is irrelevant as long as you can compare and record the outputs of the two otherwise identical arrays, one tracked and one fixed.
    Do I understand this right? If so, it's good real-world data for design purposes.
    Allan

    Allan Sindelar
    Allan at positiveenergysolar.com
    NABCEP Certified Photovoltaic Installer
    EE98J Journeyman Electrician
    Positive Energy, Inc.
    3201 Calle Marie
    Santa Fe, New Mexico 87507
    505 424-1112
    www.positiveenergysolar.com

    Dana Orzel wrote: 

    This is for a grid tied with battery backup Outback system.

    The 32% increased gain for the tracker VS. fixed mount production is an average of the last 180 days and I checked it in the spring for the last 180 days [over the winter] and it was 33%. The 12 - Evergreen 180 watt modules produce about 65 -70% of our home and office's electrical requirements.

    Thanks,

    Dana Orzel

      Dana,

      That 32% is a very useful number, and it matches with our experience as well. But I need to verify a couple of assumptions, please:

      Does this represent average annual production, rather than peak seasonal? And is it a grid-tied system?

      Thanks,

      Allan

      Allan Sindelar

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