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What's wrong with tracking on large solar arrays?

  • 1.  What's wrong with tracking on large solar arrays?

    Posted 03-16-2022 08:58 AM
    I am no expert, just trying to understand.  When I see pictures of large solar arrays, the panels are stacked together in a way that would make efficient solar tracking impossible.  Tracking should allow efficient collection over a wider period of the day, thereby reducing the need for expensive storage.  Are power companies stupid?  What am I missing?

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    Ernie Rogers
    Partner
    ernie.e.rogers@gmail.com
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  • 2.  RE: What's wrong with tracking on large solar arrays?

    ASES Life Member
    Posted 03-17-2022 09:19 AM
    GCR -  ground cover ratio - can be deceptive when a photographer is trying to show off the panels at an angle that hides the space between.

    Next time you play with https://pvwatts.nrel.gov, on "System Info" page, "Advanced Parameters", "Ground Cover Ratio:", you'll see a current default of ".4" - 40% of the ground is covered with panels. In utility scale solar, single-axis backtracking arrays are very common, and in Albuquerque, utility scale fields have used 33% coverage to maximize early morning and late afternoon energy production to better match the two daily peaks.  Land cost might push for more coverage at the expense of maximal energy production.

    PVWatts includes handy "i" information buttons as a built in tutorial, thank you NREL!


    Andrew Stone
    Commercial Solar Lending











  • 3.  RE: What's wrong with tracking on large solar arrays?

    Chapter Leader
    Posted 03-17-2022 09:20 AM
    Ernie - As you know the 'tracking' mechanism is 'mechanical' and will tend to break down regularly ! If you have a tracking PV array, on a small scale the problem may be accessible for repairs ! On a large scale the mechanical apparatus involved may not break down, but when it does, it's beyond the scale that would make it easy to repair ! Therefore, the size of many community solar projects allow for the advantage of simple south facing PV array, in addition to the slant angle of 'latitude (+/-) 15 degrees' will be optimum for these PV projects ! I work with small scale, 'off-grid' solar and do appreciate your question !

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    John Burke
    Director, MESEA, Maine
    Maine Solar Energy Association; Downeast Alternative Design Solar, Inc
    Jonesport ME
    dadsolar@yahoo.com
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  • 4.  RE: What's wrong with tracking on large solar arrays?

    Posted 03-17-2022 09:49 AM
    Hey, John, thanks for the reply.
          If you are right on the reason, that just means to me that this is a problem that needs attention--to develop a reliable, low-cost tracking system.  Only one-axis tracking is enough to gain 90% of the benefit.  But, I would imagine that someone has already published a paper digging into this question.
          Hey, you live way up north.  Long summer days should be very good for tracking.

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    Ernie Rogers
    Partner
    ernie.e.rogers@gmail.com
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  • 5.  RE: What's wrong with tracking on large solar arrays?

    Chapter Leader
    Posted 03-21-2022 10:54 AM
    Ernie - We do live 'up north' in the most northern state in the US, (other that Alaska !) ... although we're in the 'furthest East', and 'Downeast' as they say ! (We're as far south as you can go, when you're at the 'far eastern' ... Washington County, Maine) ... "The Sunrise County, USA" ! Of course we do get the earliest 'sunset' as well ! We have a small, 'off-grid' PV array on the passive solar 'owner built' home ... here on the coast of Maine, Jonesport. The four 240W PV modules give the 'required' electric power we desire here ! Tracking has it's advantage in some circumstances, but I stand by the 'old adage' ... You are better off with additional PV modules, (as others have agreed with me here), than the possible 'headache' of a tracking system ('mechanical breakdown'), ... and if you happen to be 'away' ... then you may almost cut you PV power completely 'OFF' ! ... since how often would a tracker 'quit' when the modules are facing directly South' ??? Keep up the effort for an 'inexpensive, fool-proof' tracking system ! Thank you

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    John Burke
    Director, MESEA, Maine
    Maine Solar Energy Association; Downeast Alternative Design Solar, Inc
    Jonesport ME
    dadsolar@yahoo.com
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  • 6.  RE: What's wrong with tracking on large solar arrays?

    Posted 03-17-2022 10:35 AM
    solar tracking, if used in a LARGE, array, is generally setup as E/W tracking only. By using only a single axis, more panels can be moved, with less energy, less cost, and better wind resistance.  2 axis tracking is a VERY expensive installation cost, and on a UTILITY SCALE would be cost prohibitive. With the significant reduction in cost of panels, simply installing an extra 15% of panels on a fixed array gathers the equivalent of a much smaller array that is tracking. The MONEY NUMBERS just don't work out in favor of any tracking other than single axis - and even with single axis tracking, the MAINTENANCE COST is a very significant part of the lifetime operation expense. it all boils down to math, money, profit and payback time.

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    Joe Utasi
    PV Solar Consultant
    Cinci Home Solar, Keowee Home Solar, DIY Solar Helper
    joe@cincihomesolar.com
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  • 7.  RE: What's wrong with tracking on large solar arrays?

    Posted 03-17-2022 11:18 AM
    Dual axis tracking is possible.  Due to the additional installation and maintenance cost, it is usually more cost effective to use a fixed ground mount to obtain the same amount of electrical energy.

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    Stu Besnoff
    owner
    Alpine Solar Heat and Hot Water, LLC
    stu@AlpineSolarHeat.com
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  • 8.  RE: What's wrong with tracking on large solar arrays?

    Posted 03-17-2022 05:12 PM
    There is nothing wrong with tracking per-say.  It is just that extra movmement adds GREATLY to the cost of a system and then adds maintenance to what is normally maintenance free.  It is just much more cost effective to add a few more panels to a fixed array.

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    David Hrivnak
    Sales/Engineering
    EcoLogical (part time)
    dhrivnak@chartertn.net
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  • 9.  RE: What's wrong with tracking on large solar arrays?

    Posted 03-18-2022 03:55 PM
    In a nutshell,...
    Bankability and LCOE are gods in utility scale solar.

    Complexity robs profits if not cost justified. It is cheaper to simply orient more fixed panels toward the most profitable azimuth. For us in the western US,..that means WEST.

    Tracking typically only makes sense when you are space constrained.

    Vic Aguilar
    Sustainable Energy Consultant
    NABCEP COK#081309
    (626)633-6682
    Please consider your environmental responsibility. Before printing this e-mail message, ask yourself whether you really need a hard copy.






  • 10.  RE: What's wrong with tracking on large solar arrays?

    Posted 03-21-2022 09:44 AM
    Mar 18, 2022 3:55 PM
    https://community.ases.org/network/members/profile?UserKey=d77f39fd-47d3-4768-9490-7761bdeece0e. Click or tap to follow the link." data-linkindex="30" style="margin: 0px; color: rgb(87, 177, 181); text-decoration: underline">Victor Aguilar
    Question - How is WEST the most profitable? >  Would not 50% of each day and a large amount of gain in the winter months be lost? 


    Mar 18, 2022 3:55 PM
    https://community.ases.org/network/members/profile?UserKey=d77f39fd-47d3-4768-9490-7761bdeece0e. Click or tap to follow the link." data-linkindex="30" style="margin: 0px; color: rgb(87, 177, 181); text-decoration: underline">Victor Aguilar
    In a nutshell,...
    Bankability and LCOE are gods in utility scale solar.

    Complexity robs profits if not cost justified. It is cheaper to simply orient more fixed panels toward the most profitable azimuth. For us in the western US,..that means WEST.

    Tracking typically only makes sense when you are space constrained.

    Vic Aguilar
    Sustainable Energy Consultant






  • 11.  RE: What's wrong with tracking on large solar arrays?

    Posted 03-22-2022 06:18 PM
    South orientation will produce the most energy but West can be more profitable depending on the Time-of-Day rates of the utility. A West orientation delays the peak production time by several hours compared to a South orientation. If the electric usage is higher in the late afternoon/early evening when it is hotter and more air conditioners are on, and the utility rates are higher to compensate for this, then it could make economic sense to orient your panels to the West.

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    Thomas Grant
    Director
    XanaduEnergy
    Fairway KS
    tjg4@aol.com
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  • 12.  RE: What's wrong with tracking on large solar arrays?

    Silver
    Contributor
    Posted 03-22-2022 10:39 AM
    Edited by william fitch 03-22-2022 07:35 PM
    A quick note. Be careful when having all these "what's the best" conversations. What is most profitable may not mean maximum production, especially in commercial arrays. I would stay away from all financial aspects, especially for res and focus on site maximum production (Engineering). Other wise things like 'West is best' can seem off the rails... The RE goal is to produce as much energy as possible which will yield the maximum displacement of FF. Focusing on the money is the wrong primary reason. Design for max efficiency and max power but meeting the engineering requirements for the particular system design and function. A justifiable reason for choosing a flatter production profile might be when an array is being designed to charge batteries. A longer flat curve might be better than a peak'ie curve despite yielding more energy. There are other engineering situations which also could arise, etc.. Tracking over the course of a day yields a much flatter profile and yields the most energy per KW installed. The challenge with tracking is wind loadings. Over design for that along with the movement engineering and maint. will be minimized. 

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    william fitch
    Owner
    www.WeAreSolar.com
    fcfcfc@ptd.net
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  • 13.  RE: What's wrong with tracking on large solar arrays?

    ASES Life Member
    Posted 03-23-2022 12:20 PM
      |   view attached
    Bill Fitch makes a good point. There is no single metric of 'best'. A paper from the now defunct Solar Pro magazine (issue 11.1 2018) authored by Paul Grana called 'Design Optimization in Constrained Applications' makes the case that the same commercial rooftop could have three different installations depending on the goal. I attached it here. See table below. You can optimized for different constraints:  by area, budget, or power injections.  Can result in different tilt, kW installed, energy produced. And in net revenue or NPV. Similar with tracking.

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    Steven Hegedus
    Professor and Senior Scientist
    University of Delaware
    Newark Delaware
    ssh@udel.edu
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  • 14.  RE: What's wrong with tracking on large solar arrays?

    Chapter Leader
    Posted 03-23-2022 12:41 PM