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Posted by Robert on May 14, 2008, 5:53 pm

You mean summer.  The tracker wouldn't have to move very far in winter
at 66N latitude.  I'm sure we could come up with a workaround in
summer -- swivel 360 degrees, then make a quick adjustment
counterclockwise and restart.  Anyway, I was trying to be humorous, as
I assume you are also.

Posted by Bob on May 14, 2008, 5:45 pm
Robert wrote:

The roof is "5 and 12" so the panels point 24 degrees from vertical,
which means 66 degrees from horizontal. Sorry if I have the elevation
convention backwards.
I'm in San Jose, CA.
** Posted from http://www.teranews.com  **

Posted by Robert on May 14, 2008, 6:41 pm
I would call 66 degrees from the horizontal, 66 degrees tilt or
elevation.  (Actually arctan 12/5 = 67.4 degrees.  You have a 5, 12,
13 Pythagorean triple.)  It can be a bit confusing, e.g., the solar
zenith angle, Z, is measured from the vertical.
San Jose, approx. 37 degrees N, 37 degrees "tilt from horizontal" (the
phrase used in this link) would be optimal
Your roof is steep even for winter, but if you ever move to the arctic
circle, take your roof with you.
Just to be sure, your roof has a 12' vertical rise in a horizontal
distance of 5' ?  And I did look at your profile, it is public, and
there were posts about ski conditions in Norway, so I thought that fit
with the 66 degree tilt.  Sometimes it is hard to put 2 and 2


Posted by Bob on May 14, 2008, 10:28 pm
 Robert wrote:


Sorry, I'll try again ;-) the normal vector to the panels (an imaginary
line that is perpendicular to the panel face) points 22.6 degrees away
from vertical. Though I would like to xc ski in Norway sometime, I live
in California in a typical 1920s "bungalow" style house - in
roofing-speak the "rise" is 5 and the "run" is 12 ;-) This angle stuff
gets confusing fast!

** Posted from http://www.teranews.com  **

Posted by dold on May 21, 2008, 2:46 pm
I used to manually track my Fronius readings every day.  By comparing the
minutes of run time "today' and "total" verses yesterday's readings, I
calculated the start and stop times.  I recall that those were before/after
sunrise/set.  I have also observed readings of 30-90 watts before and after
official sunrise/sunset, although that was not true last night.  At about
"sunset", it had already shut down, and was attempting to restart, which it
does a few times.

That may be because the sunrise azimuth is way "behind" my solar panel at
this time of year.  It looks like 61 degrees at 5:55am PDT today, and my
panels are at 217.  On January 6th, it looks like sunrise is 7:28am PST at
118 azimuth.  Maybe it would be generating energy in the pre-sunrise time
with that initial exposure, although that start time would be later in the
day than the post-sunrise time at a different time of year.

Clarence A Dold - Hidden Valley Lake, CA, USA  GPS: 38.8,-122.5
http://cdold.home.mchsi.com/Solar-generation.htm  $705 avoided in 2007.

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