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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Do the Enphase inverters clip the output power to their rating
like other manufacturer’s? So a M190 can only put out 190 watts max? I
have had this question for a bit now on system performances using Enphase in
designs during our cold spring and fall days.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:navy'>Sincerely,<br>
<br>
Chris Worcester<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:navy'>Solar Wind Works<br>
NABCEP Certified PV Installer<br>
Phone: 530-582-4503<br>
Fax: 530-582-4603<br>
<a href="http://www.solarwindworks.com/">www.solarwindworks.com</a><br>
<a href="mailto:chris@solarwindworks.com">chris@solarwindworks.com</a><br>
"Proven Energy Solutions"</span><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p>
</div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";
color:windowtext'>From:</span></b><span style='font-size:10.0pt;font-family:
"Tahoma","sans-serif";color:windowtext'>
re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>Mark
Westbrock<br>
<b>Sent:</b> Friday, May 07, 2010 10:33 AM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] Enphase performance<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The over-reporting of energy that Randy refers to below was
much higher than any discrepancy based on monitoring resolution. We have
a pyranometer at the site, and Enphase reported energy production as high as
38% higher that predicted from irradiance data, as well as 38% higher than the
string inverter portion of the same system. Individual microinverters
showed instantaneous power output as high as 285 W from a nominal 190 W unit.<br>
<br>
Enphase explained that there was a software glitch that was resulting in
"double counting". It took them over two months to correct this
issue, time which is lost from our experimental comparison of string vs.
microinverter. They indicated that this seemed to be an isolated situation,
but I wonder how many Enphase customers are reporting miraculous performance
from their system without verifying via another meter.<br>
<br>
Screen shot of a day's power production of 22 M190 microinverters (nominal 4180
watts AC):<br>
<img border=0 width=469 height=286 id="_x0000_i1025"
src="cid:image001.jpg@01CAEE05.2D8DDF00"><br>
<br>
Mark<br>
<br>
<o:p></o:p></p>
<pre>Mark Westbrock<o:p></o:p></pre><pre>NABCEP Certified Solar PV Installer<o:p></o:p></pre><pre>NM ER-1J Journeyman Electrician<o:p></o:p></pre><pre>Positive Energy, Inc.<o:p></o:p></pre><pre>office: 575-524-2030<o:p></o:p></pre><pre>cell: 575-640-2432<o:p></o:p></pre><pre><a
href="mailto:westbrock@positiveenergysolar.com">westbrock@positiveenergysolar.com</a><o:p></o:p></pre><pre><a
href="http://www.positiveenergysolar.com">www.positiveenergysolar.com</a><o:p></o:p></pre>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='color:#1F497D'>We definitely experienced an overstatement. </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='color:#1F497D'> </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='color:#1F497D'>We have a client who installed 5kW on a string inverter
and 5kW on enphase and it is that side-by-side comparison that enabled us to
positively identify a problem. There was a significant overstatement of output.
We finally got a Enphase person who told us it was a software glitch. The
problem appears to be fixed. They explained to us that our problem was
isolated without giving us a detailed explanation of what happened. Since
that problem was fixed, we have seen no difference in output between a string
inverter and enphase.</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='color:#1F497D'> </span><o:p></o:p></p>
<p class=MsoNormal><span style='color:#1F497D'>Randy<br>
<br>
</span>Kirpal Khalsa wrote: <o:p></o:p></p>
<p class=MsoNormal>This same issue has come up over the years for us......first
with PV Powered inverters and then noticed in Fronius as well......We have
noticed in most of our grid tied systems that are connected thru a
"revenue grade meter" for Oregon Energy Trust production reporting,
that the inverter always has a higher performance than indicated on the
"utility grade meter". We have seen the discrepency as
high as 10%. Over time this adds up to significant kWh
differences. In our experience the inverter always has the higher kWh
reporting, we have attributed this to the inverter wanting to report a good
production number, to boost their efficiency claims......maybe even more than
is accurate.....I have asked PV Powered and Fronius about this and their line
is that to put a "revenue grade meter" into the inverter would be
cost prohibitive......interesting as the readily available revenue grade meters
are only $30-$60. I would gladly pay that much extra if I didn't
have to wire in an additional meter. <br>
I don't think this problem is unique to the Enphase units (i haven't installed
any of these), I think all inverters should be required to install the revenue
grade meters to give accurate reporting of actual production.
Similar to how states have a "weights and scales" accuracy
certification, energy consumption and production meters should be similarly
calibratable. <br>
<br>
-- <br>
Sunny Regards,<br>
Kirpal Khalsa<br>
NABCEP Certified Solar PV Installer<br>
Renewable Energy Systems<br>
<a href="http://www.oregonsolarworks.com">www.oregonsolarworks.com</a><br>
541-218-0201 m<br>
541-592-3958 o<br>
<br>
<o:p></o:p></p>
<pre><o:p> </o:p></pre><pre style='text-align:center'>
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