<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">Hi Jim,<br><br>I like using one of the design emulators for just this reason. PVSYST and PVSOL. You can model each scenario and see how the numbers crunch. You import historical weather data for the region to get as accurate as possible. <br><br>You mention the silver painted roof, these emulators allow you to input albedo affects, too.<br><br>Both packages offer free trial periods, so you could run just this case for free. If you like them then you spend the money for the license. <br><br><br><br>-Wes Kennedy<br>NABCEP certified PV Installer<br>
303-653-3073<br><br>--- On <b>Mon, 4/19/10, Jim MacDonald <i><jmac@solaresystems.com></i></b> wrote:<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>From: Jim MacDonald <jmac@solaresystems.com><br>Subject: Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string?<br>To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org><br>Date: Monday, April 19, 2010, 5:40 PM<br><br><div id="yiv586268752">
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<p class="MsoNormal"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">SB8000US only good for 480 Vac, we’re tying in at 208.</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">11 strings has been calc’d to be OK (<600vdc) for record low -4
fahrenheit (-20 celsius).</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">I think the big concern as mentioned is getting the Voc high
early in the AM to wake the inverter up, also maintaining the Vmp later in the
day to keep it running for as long as possible into the late afternoon/
evening.</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">Will those extra kWh gleaned in the early AM/ late PM over the
course of 365 days be more than the kWh clipped during peak production times
with the 9.075 kWdc?</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">NYC average summer highs between 79 and 84 fahrenheit early
june-late august. Sunlink rack @ 10</span>° <span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">on a silver-painted built-up
roof.</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">Time-of-use utility $ peak-shaving is not an issue here.</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);">Thank you</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="font-size: 11pt; font-family: "sans-serif"; color: rgb(31, 73, 125);"> </span></p>
<div style="border-right: medium none; border-width: 1pt medium medium; border-style: solid none none; border-color: rgb(181, 196, 223) -moz-use-text-color -moz-use-text-color; padding: 3pt 0in 0in;">
<p class="MsoNormal"><b><span style="font-size: 10pt; font-family: "sans-serif";">From:</span></b><span style="font-size: 10pt; font-family: "sans-serif";">
re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>Darryl
Thayer<br>
<b>Sent:</b> Monday, April 19, 2010 5:58 PM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod
per string?</span></p>
</div>
<p class="MsoNormal"> </p>
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<p class="MsoNormal">The temperature correction is the concern. I have
heard lots of stories of inverters dieing when it gets to cold. Look in
the code book 690.7 at the temperature correction table. Go to
weather.com and find your record low temperature. Find you Tc factor
and will your senerios work? I have heard from a sunny boy rep that it
is OK to over power by 1.25% </p>
</div>
<div>
<p class="MsoNormal">darryl<br>
<br>
--- On <b>Mon, 4/19/10, Dana <i><dana@solarwork.com></i></b> wrote:</p>
</div>
<blockquote style="border-width: medium medium medium 1.5pt; border-style: none none none solid; border-color: -moz-use-text-color -moz-use-text-color -moz-use-text-color rgb(16, 16, 255); padding: 0in 0in 0in 4pt; margin-left: 3.75pt; margin-top: 5pt; margin-bottom: 5pt;">
<p class="MsoNormal" style="margin-bottom: 12pt;"><br>
From: Dana <dana@solarwork.com><br>
Subject: Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per
string?<br>
To: "'RE-wrenches'" <re-wrenches@lists.re-wrenches.org><br>
Date: Monday, April 19, 2010, 4:31 PM</p>
<div id="yiv1929680234">
<div>
<p class="MsoNormal" style=""><span style="font-size: 14pt; font-family: "sans-serif";">Many times we
switch to another module manufacturer as one will not fit or another inverter
manufacturer. </span></p>
</div>
<p class="MsoNormal" style=""><span style="font-size: 14pt; font-family: "sans-serif";">PVPowered has a
more relaxed window and we have had fine success with them when SMA does not
fit. </span></p>
</div>
<p class="MsoNormal" style=""><span style="font-size: 14pt; font-family: "sans-serif";">Cold is the
dictator and the 600 VDC threshold.</span></p>
</blockquote>
<p class="MsoNormal" style=""><span style="font-size: 14pt; font-family: "sans-serif";"> </span></p>
<p class="MsoNormal" style=""><span style="font-size: 14pt; font-family: "sans-serif";"> </span></p>
<div>
<p class="MsoNormal" style=""><span style="font-family: "sans-serif";">Thanks, Dana Orzel</span></p>
</div>
<p class="MsoNormal" style=""><span style="font-family: "sans-serif";"> </span></p>
<p class="MsoNormal" style=""><span style="font-family: "sans-serif";">Great Solar Works, Inc</span></p>
<p class="MsoNormal" style=""><span style="font-family: "sans-serif";">web - www.solarwork.com</span></p>
<p class="MsoNormal" style=""><span style="font-family: "sans-serif";">E - dana@solarwork.com</span></p>
<p class="MsoNormal" style=""><span style="font-family: "sans-serif";">V - 970.626.5253</span></p>
<p class="MsoNormal" style=""><span style="font-family: "sans-serif";">F - 970.626.4140</span></p>
<p class="MsoNormal" style=""><span style="font-family: "sans-serif";">C - 970.209.4076</span></p>
<p class="MsoNormal" style=""><span style="font-family: "sans-serif";"> </span></p>
<p class="MsoNormal" style=""><span style="font-family: "sans-serif";">"We have been slow to give up
on the myth of the Earth's generosity.</span></p>
<p class="MsoNormal" style=""><span style="font-family: "sans-serif";">Rather grandly, we have overdrawn
our accounts."</span></p>
<p class="MsoNormal" style=""><span style="font-family: "sans-serif";">Barbara Kingsolver - Water is life.</span></p>
<p class="MsoNormal" style=""><span style="font-size: 14pt; font-family: "sans-serif";"> </span></p>
<div>
<div style="border-right: medium none; border-width: 1pt medium medium; border-style: solid none none; border-color: rgb(181, 196, 223) -moz-use-text-color -moz-use-text-color; padding: 3pt 0in 0in;">
<p class="MsoNormal" style="margin-left: 0.5in;"><b><span style="font-size: 10pt; font-family: "sans-serif";">From:</span></b><span style="font-size: 10pt; font-family: "sans-serif";">
re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>Jim
MacDonald<br>
<b>Sent:</b> Monday, April 19, 2010 2:37 PM<br>
<b>To:</b> RE-wrenches@lists.re-wrenches.org<br>
<b>Subject:</b> [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per
string?</span></p>
</div>
</div>
<p class="MsoNormal" style="margin-left: 0.5in;"> </p>
<p class="MsoNormal" style="margin-left: 0.5in;">For a straight grid-tie system@ 10 degree tilt, 180
azimuth, zero/little shade, NYC avg 4.29 kWh/m²/day.</p>
<p class="MsoNormal" style="margin-left: 0.5in;"> </p>
<p class="MsoNormal" style="margin-left: 0.5in;">Feed an SMA7000 with (3) strings of 11 Suntech STP275’s
[9.075 kWdc]</p>
<p class="MsoNormal" style="margin-left: 0.5in;">Or</p>
<p class="MsoNormal" style="margin-left: 0.5in;">Do strings of 10, so itd be 8.250 kWdc into the 7 kWac
inverter.</p>
<p class="MsoNormal" style="margin-left: 0.5in;"> </p>
<p class="MsoNormal" style="margin-left: 0.5in;">Strings of 11= 491.7 Voc; 386 Vmp</p>
<p class="MsoNormal" style="margin-left: 0.5in;">Strings of 10= 447 Voc; 351 Vmp </p>
<p class="MsoNormal" style="margin-left: 0.5in;"> </p>
<p class="MsoNormal" style="margin-left: 0.5in;">The tradeoff would be power clipping at/around noon in the
sunny months in the 9.075 kW scenario;</p>
<p class="MsoNormal" style="margin-left: 0.5in;">Inverter sleeping late every morning and retiring early in
the evenings in the lowered voltage scenario.</p>
<p class="MsoNormal" style="margin-left: 0.5in;"> </p>
<p class="MsoNormal" style="margin-left: 0.5in;">Trying to figure out which would yield more kWh at the end
of the year.</p>
<p class="MsoNormal" style="margin-left: 0.5in;"> </p>
<p class="MsoNormal" style="margin-left: 0.5in;">Any ideas appreciated,</p>
<p class="MsoNormal" style="margin-left: 0.5in;">thanks</p>
<p class="MsoNormal" style="margin-left: 0.5in;"> </p>
<p class="MsoNormal" style="margin-left: 0.5in;"> </p>
<p class="MsoNormal" style="margin-left: 0.5in;"> </p>
<p class="MsoNormal" style="margin-left: 0.5in;"> </p>
<p class="MsoNormal" style="margin-left: 0.5in;"><b><span style="font-size: 10pt; font-family: "sans-serif"; color: rgb(0, 32, 96);">Jim MacDonald</span></b></p>
<p class="MsoNormal" style="margin-left: 0.5in;"><span style="font-size: 10pt; font-family: "sans-serif"; color: rgb(0, 32, 96);">Solar Energy Systems, LLC</span></p>
<p class="MsoNormal" style="margin-left: 0.5in;"><span style="font-size: 10pt; font-family: "sans-serif"; color: rgb(0, 32, 96);">Brooklyn, NY 11222</span></p>
<p class="MsoNormal" style="margin-left: 0.5in;"><span style="font-size: 10pt; font-family: "sans-serif"; color: rgb(31, 73, 125);"><a rel="nofollow" target="_blank" href="http://www.solaresystems.com/"><u><span style="color: blue;">www.solarEsystems.com</span></u></a></span></p>
<p class="MsoNormal" style="margin-left: 0.5in;"> </p>
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