<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>I did play around with numbers on there and came to that conclusion. Considering I'm only 50 miles from international falls, it's even a clearer choice then running the numbers in the cites. </div><div><br></div><div>Verification is always nice!</div><div><br></div><div>Jesse<br><br>Sent from my iPhone</div><div><br>On May 15, 2013, at 5:59 PM, Kent Osterberg <<a href="mailto:kent@coveoregon.com">kent@coveoregon.com</a>> wrote:<br><br></div><blockquote type="cite"><div>
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<div class="moz-cite-prefix">Jesse,<br>
<br>
Running PVWatts for various tilt angles with an azimuth angle of
135° (or 225°) for locations in <font size="3">Minneapolis</font>,
shows that the optimum tilt angle for annual energy production is
about 35°, that's almost the same as the optimum tilt with an
azimuth of 180°. To maximize December energy production with the
135° azimuth, the optimum tilt angle is about 60° and that gives
12% more energy in December than the 35° tilt would (without
considering how much better the steep tilt does at shedding snow).
The SE roof with the steeper pitch is certainly the better choice.<br>
<br>
<pre class="moz-signature" cols="72">Kent Osterberg
Blue Mountain Solar, Inc.
<a class="moz-txt-link-abbreviated" href="http://www.bluemountainsolar.com">www.bluemountainsolar.com</a>
</pre>
On 5/14/2013 8:23 PM, Jesse Dahl wrote:<br>
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<div>Allan,</div>
<div><br>
</div>
<div>That is pretty much my thinking. They have 0 interest in
stepping foot roof and the SE give more tilt and easy ground
access to clear the array during winter. </div>
<div><br>
</div>
<div>I appreciate the advice. </div>
<div><br>
</div>
<div><br>
</div>
<div>Jesse<br>
<br>
Sent from my iPhone</div>
<div><br>
On May 14, 2013, at 10:15 PM, Allan Sindelar <<a moz-do-not-send="true" href="mailto:allan@positiveenergysolar.com">allan@positiveenergysolar.com</a>>
wrote:<br>
<br>
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<div class="moz-cite-prefix">Jesse,<br>
Based only on the info you provided, I'd recommend the SE
face. A low slope is best for maximizing annual gain, which
is what a conventional grid-tie customer would want. But you
are in essence giving them a system that will function as GT
now, but as an off grid system if the grid goes down. Under
that scenario, I would sacrifice annual
spin-the-meter-backward production in favor of maximizing
winter output, when days are shortest and loads are
greatest. A steeper array pitch will maximize available
charge during winter, while the shallow pitch will be great
in summer but close to nothing in winter. Given their stated
objective, explain the tradeoff as offering the best
preparation for lack of grid.<br>
<br>
I'd advise otherwise if they clearly want to seasonally
adjust their array if there is an outage, and you install
adjustable-tilt racks, and the owners are afraid of neither
ladders, heights, or snow.<br>
<br>
We just completed a 4 kW GTBB system for a customer with
similar objectives. We used 16 240W modules on two 8-module
pole-top racks, with the instruction to leave the tilt angle
shallow as long as the utility is present, but tilt to 45-55
degrees in winter during an extended outage. (And a pair of
Classic 200s to handle the 4-module series strings.)<br>
Allan<br>
<br>
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<font face="Times New Roman, Times, serif"><b>Allan
Sindelar</b></font><br>
<small><a moz-do-not-send="true" href="mailto:Allan@positiveenergysolar.com"><font color="#000099" face="Times New Roman, Times, serif"><u>Allan@positiveenergysolar.com</u></font></a></small><font face="Times New Roman, Times, serif"><br>
<span style="font-size: 10pt;">NABCEP Certified
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On 5/14/2013 4:34 PM, Jesse Dahl wrote:<br>
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<blockquote cite="mid:E43E2313-9908-482A-BE64-F1512811F504@gmail.com" type="cite">
<pre wrap="">Hello,
I was asked to look at a site today for a homeowner looking for a grid-tie with battery-back up. They are Doomsday Preppers for lack of a better term and want certain loads if and when the grid goes down for good. Aside from parts selection, they have two roof lines, one facing SE one facing SW. the SW is very low slope and is only accessible with a ladder and climbing on the roof, the other is SE, much steeper slope and accessible from the ground or deck. I mention the access because of snow removal. We had lots of snow last year and I spent lots of time on my roof removing 8" snow falls. Both have good solar access.
I'm inclined to chose the SE roof line, but I am interested in arguments for the SW.
Thanks!
Jesse
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