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<font face="Verdana">Dana, Marco, Wrenches,<br>
<br>
In most locations, if the interest is in maximum lifetime energy
production, it does make sense to use modules with STC power ratings
significantly higher than the inverter max power rating.<br>
<br>
This is explained in the whitepaper located at:<br>
<br>
<a class="moz-txt-link-freetext" href="http://www.enphaseenergy.com/downloads/Enphase_White_Paper_Module_Rightsizing.pdf">http://www.enphaseenergy.com/downloads/Enphase_White_Paper_Module_Rightsizing.pdf</a><br>
<br>
Remember, under most real world conditions the module will not produce
STC rated power. The inverter WILL produce maximum rated power plus
some small percent to allow for the CEC max power test methods. Also,
the module will produce less power every year (under the same
conditions) and the inverter will produce its' max rated power for its'
entire lifetime.<br>
<br>
By the way, this all applies to string, central, or microinverters. Of
course, micros still retain the advantages of dealing with mismatch,
partial shading/soiling, etc.<br>
<br>
Bottom line is, the "perfect" match will depend on your particular
installation.<br>
<br>
</font>
<pre class="moz-signature" cols="72">See ya!
Marv
707 763-4784 x7016
</pre>
<br>
<br>
Dana Brandt wrote:
<blockquote
cite="mid:AANLkTimpSHbIovWYSuGW58UGziJyoLcoUo1H4QAdpjFK@mail.gmail.com"
type="cite">Something to remember is that my simulation was for a
specific location in Washington. The answer might be different for your
location and weather patterns.<br>
<br>
I agree that it seems wrong to have the inverter rating 20% less than
the array nameplate. Typically, I would consider that sort of pairing a
poor design. You're right that there will certainly be some clipping -
especially with cloud-edge effects. The real question in my mind is not
whether the inverter will ever clip the output of the array, but what's
the real impact of that on energy generation on an annual basis. This
is what lead me to do the modeling simulations which indicated the
effect is negligible when taken in the context of the total annual
production. Compared to the whole year's sun, there just isn't that
much energy in high production spikes like cloud edge effects that the
inverters will clip - at least not around here. <br>
<br>
One thing to consider is that if you go with smaller modules you need
more inverters. You might compare the cost of the additional inverters
to the value of the 0.2% energy loss from clipping over the lifetime of
the system. <br>
<br>
Dana<br clear="all">
<br>
<br>
Dana Brandt<br>
Ecotech Energy Systems, LLC<br>
<a moz-do-not-send="true" href="http://www.ecotechenergy.com">www.ecotechenergy.com</a><br>
<a moz-do-not-send="true" href="mailto:dana@ecotechenergy.com">dana@ecotechenergy.com</a><br>
360.510.0433<br>
<br>
<br>
<div class="gmail_quote">On Mon, May 10, 2010 at 11:36 AM, Marco
Mangelsdorf <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:marco@pvthawaii.com">marco@pvthawaii.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div link="blue" vlink="purple" lang="EN-US">
<div>
<div
style="border-style: solid none none; border-color: rgb(181, 196, 223) -moz-use-text-color -moz-use-text-color; border-width: 1pt medium medium; padding: 3pt 0in 0in;">
<p class="MsoNormal"><span
style="font-size: 11pt; color: rgb(31, 73, 125);">I just don’t
understand why going over 20 percent of
module nameplate to nameplate inverter rating makes any sense.</span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; color: rgb(31, 73, 125);">I regularly see
120-130 percent of nameplate amperage coming off
of the array on our office due to edge of cloud.</span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; color: rgb(31, 73, 125);">So I have to
disagree with Dana in this instance. I see
this a bad design especially since lower output mods are so readily
available
these days.</span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; color: rgb(31, 73, 125);">And what’s up with
the Enphase 210? Doesn’t it
say on their latest compatibility list (March 2010) that it’s only good
for the Sanyo line? What’s up with that especially since I know
that one other manufacturer is signing off on using the Enphase 210
with their
210-watt module, apparently with Enphase’s approval?</span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; color: rgb(31, 73, 125);">Marv—why is your
Enphase 210 only listed for use with the
Sanyo line when there’s a growing number of 210+ watt mods out there
these days?</span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; color: rgb(31, 73, 125);">Thanks,</span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; color: rgb(31, 73, 125);">marco</span><span
style="font-size: 10pt;"></span></p>
</div>
<div>
<div class="h5">
<p class="MsoNormal"> </p>
<p class="MsoNormal" style="margin-bottom: 12pt;">I've been
concerned about
pairing higher wattage modules (~230W) with the 190W Enphase fearing a
lot of
clipping and power loss when the modules are at full power. <br>
<br>
I did some modeling of this setup in PVSYST and found that the expected
loss
from the inverter being underpowered is 0 - 0.2% annually depending on
the
assumptions. The modeling was for northwestern Washington State. A
fifth of a percent
seems pretty negligible to me and is easily offset by removing module
mismatch
from the equation. So, I'm convinced that matching modules in the 230W
range
with the 190W Enphase inverters is a good design.<br>
<br>
I recently installed 4kW of 230s with the Enphase 190s and have seen
their
output as high as 199W. <br clear="all">
<br>
Dana<br>
<br>
<br>
Dana Brandt<br>
Ecotech Energy Systems, LLC<br>
<a moz-do-not-send="true" href="http://www.ecotechenergy.com"
target="_blank">www.ecotechenergy.com</a><br>
<a moz-do-not-send="true" href="mailto:dana@ecotechenergy.com"
target="_blank">dana@ecotechenergy.com</a><br>
360.510.0433<br>
<br>
</p>
</div>
</div>
<div>
<div>
<div class="h5">
<p class="MsoNormal">On Fri, May 7, 2010 at 4:48 PM, Chris
Worcester <<a moz-do-not-send="true"
href="mailto:chris@solarwindworks.com" target="_blank">chris@solarwindworks.com</a>>
wrote:</p>
</div>
</div>
<div>
<div>
<div>
<div class="h5">
<p class="MsoNormal"><span
style="font-size: 11pt; color: rgb(31, 73, 125);">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.</span></p>
<div>
<p class="MsoNormal"><span
style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<div>
<p class="MsoNormal"><span style="font-size: 10pt; color: navy;">Sincerely,<br>
<br>
Chris Worcester</span></p>
<p class="MsoNormal"><span style="font-size: 10pt; color: navy;">Solar
Wind Works<br>
NABCEP Certified PV Installer<br>
Phone: 530-582-4503<br>
Fax: 530-582-4603<br>
<a moz-do-not-send="true" href="http://www.solarwindworks.com/"
target="_blank">www.solarwindworks.com</a><br>
<a moz-do-not-send="true" href="mailto:chris@solarwindworks.com"
target="_blank">chris@solarwindworks.com</a><br>
"Proven Energy Solutions"</span></p>
</div>
<p class="MsoNormal"><span
style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
</div>
<div>
<div
style="border-style: solid none none; border-color: -moz-use-text-color; border-width: 1pt medium medium; padding: 3pt 0in 0in;">
<p class="MsoNormal"><b><span style="font-size: 10pt;">From:</span></b><span
style="font-size: 10pt;"> <a moz-do-not-send="true"
href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>
[mailto:<a moz-do-not-send="true"
href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>]
<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</span></p>
</div>
</div>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> </p>
<div>
<div class="h5">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>
</div>
</div>
<b>Error! Filename not specified.</b><br>
<br>
Mark
<div>
<div class="h5">
<pre>Mark Westbrock</pre>
<pre>NABCEP Certified Solar PV Installer</pre>
<pre>NM ER-1J Journeyman Electrician</pre>
<pre>Positive Energy, Inc.</pre>
<pre>office: 575-524-2030</pre>
<pre>cell: 575-640-2432</pre>
<pre><a moz-do-not-send="true"
href="mailto:westbrock@positiveenergysolar.com" target="_blank">westbrock@positiveenergysolar.com</a></pre>
<pre><a moz-do-not-send="true"
href="http://www.positiveenergysolar.com" target="_blank">www.positiveenergysolar.com</a></pre>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);">We
definitely experienced an overstatement. </span></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);">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></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);">Randy<br>
<br>
</span>Kirpal Khalsa wrote: </p>
<p class="MsoNormal" style="margin-bottom: 12pt;">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 moz-do-not-send="true" href="http://www.oregonsolarworks.com"
target="_blank">www.oregonsolarworks.com</a><br>
541-218-0201 m<br>
541-592-3958 o</p>
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