<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><a href="http://PVwatts.org">PVwatts.org</a> is a wonderful website calculator for PV output that I use all the time. I and colleagues have compared its predictions with measured output in lots of situations and found it to be quite good (seems to miss some of the temperature impacts but one can normally get to within the accuracy of the inverter).<div>In Ottawa, it predicts a full 2-axis tracker will produce 36% more electricity than ideally sloped fixed system. I beleive it.</div><div><br></div><div>Oh, and I have seen literally over a hundred 6 to 10 kW two-axis tracker in southern ontario, including a dozen with a 10 km radius of my home.</div><div><br></div><div>They have the observed benefit of tilting very steeply every winter morning and evening, thereby tipping snow off very effectively. My neighbours 5 kW fixed array on the 7/12 pitch roof of his house seems to spend an awful lot of time in winter with snow cover.</div><div><br></div><div>John</div><div><br></div><div><br></div><div><div><div>On 2011-08-04, at 7:05 AM, Haudy Kazemi wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">
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I think this may be playing a role. When most people use the power
output calculators/estimators, they look at the annual production
figures not the daily figures. A tracker in a high latitude may
make larger difference in the summer than in the winter because the
arc of the sun is longer, starting in the northeast and ending in
the northwest. A fixed array in those conditions will self-shade in
the early and late parts of the day. This may the root of the daily
difference between the reported performance difference between the
tracked and non-tracked array.<br>
<br>
Roughly speaking, with guesstimate example numbers (actual values
could probably be obtained by digging into an appropriate
calculator):<br>
During summer, tracked array may outproduce the non-tracked array by
the ~40% reported in this discussion thread.<br>
During spring/fall, tracked array may outproduce non-tracked array
by 20%.<br>
During winter, with a short arc, tracked array may outproduce
non-tracked array by 5%. <br>
On an annual basis the tracked array may only exceed the non-tracked
array by ~20%, even it does better than that in the summer.<br>
<br>
Perhaps someone can check this in a calculator?<br>
<br>
<br>
<br>
On 8/3/2011 8:00 PM, Nick Pyner wrote:
<blockquote cite="mid:FHEBJOMKELIMNOKHLJJKMEDGCGAA.npyner@tig.com.au" type="cite">
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<div><span class="125304423-03082011"><font size="4">I just think
nobody is taking the geography in to account.</font></span></div>
<div><span class="125304423-03082011"></span> </div>
<div><span class="125304423-03082011"><font size="4">There are
plenty of PV installations around here, but I have never
seen or heard of a tracking one. This is probably because
there is no point in them. The situation could be quite
different in the more frigid parts of the world for two
reasons.</font></span></div>
<div><span class="125304423-03082011"></span> </div>
<div><span class="125304423-03082011"><font size="4">1. Even in
what is laughably called the banana belt of Canada, the
insolation is not that great, and the skies are not so
clear, so you would need to chase every watt you can find.</font></span></div>
<div><span class="125304423-03082011"></span> </div>
<div><span class="125304423-03082011"><font size="4">2. In the
summer, the days are longer. Hence the practical window of
opportunity may be as much as an hour wider, but the hourly
march of the sun is the same. </font></span></div>
<div><span class="125304423-03082011"></span><span class="125304423-03082011"></span> </div>
<div><span class="125304423-03082011"><font size="4">A tracking
system helps in both cases, and this heathen would imagine
the more polar you get the more sense a tracker will make. </font></span></div>
<br><p><font size="2">Nick Pyner<br>
<br>
Dee Why NSW </font></p>
<blockquote dir="ltr" style="margin-right: 0px;">
<div class="OutlookMessageHeader" dir="ltr" align="left"><font size="2" face="Tahoma">-----Original Message-----<br>
<b>From:</b> <a class="moz-txt-link-abbreviated" href="mailto:greenbuilding-bounces@lists.bioenergylists.org">greenbuilding-bounces@lists.bioenergylists.org</a>
[<a class="moz-txt-link-freetext" href="mailto:greenbuilding-bounces@lists.bioenergylists.org">mailto:greenbuilding-bounces@lists.bioenergylists.org</a>]<b>On
Behalf Of </b>RT<br>
<b>Sent:</b> Wednesday, 3 August 2011 2:59 PM<br>
</font></div><div> <br class="webkit-block-placeholder"></div><p>I told him that I had been telling people (this List) that
his single-axis tracking array had produced 40 and sometimes
44% more than the Enphase fixed array and that you (the
Listmembers) were telling me that I was full of $#!+.</p><p>We both just shrugged our shoulders (as if to say "Nyeh! What
can you do about unbelieving heathens ?") </p>
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