So why is the Enphase 210 just limited "officially" to the Sanyo
line?
Thanks,
marco
Dana, Marco, Wrenches,
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.
This is explained in the whitepaper located at:
http://www.enphaseenergy.com/downloads/Enphase_White_Paper_Module_Rightsizing.pdf
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.
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.
Bottom line is, the "perfect" match will depend on your
particular installation.
See ya!
Marv
707 763-4784 x7016
Dana Brandt wrote:
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.
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.
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.
Dana
Dana Brandt
Ecotech Energy Systems, LLC
www.ecotechenergy.com <http://www.ecotechenergy.com>
d...@ecotechenergy.com <mailto:d...@ecotechenergy.com>
360.510.0433
On Mon, May 10, 2010 at 11:36 AM, Marco Mangelsdorf
<ma...@pvthawaii.com <mailto:ma...@pvthawaii.com>> wrote:
I just don't understand why going over 20 percent of module
nameplate to nameplate inverter rating makes any sense.
I regularly see 120-130 percent of nameplate amperage coming off
of the array on our office due to edge of cloud.
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.
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?
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?
Thanks,
marco
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.
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.
I recently installed 4kW of 230s with the Enphase 190s and have
seen their output as high as 199W.
Dana
Dana Brandt
Ecotech Energy Systems, LLC
www.ecotechenergy.com <http://www.ecotechenergy.com>
d...@ecotechenergy.com <mailto:d...@ecotechenergy.com>
360.510.0433
On Fri, May 7, 2010 at 4:48 PM, Chris Worcester
<ch...@solarwindworks.com <mailto:ch...@solarwindworks.com>> wrote:
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.
Sincerely,
Chris Worcester
Solar Wind Works
NABCEP Certified PV Installer
Phone: 530-582-4503
Fax: 530-582-4603
www.solarwindworks.com <http://www.solarwindworks.com/>
ch...@solarwindworks.com <mailto:ch...@solarwindworks.com>
"Proven Energy Solutions"
*From:* re-wrenches-boun...@lists.re-wrenches.org
<mailto:re-wrenches-boun...@lists.re-wrenches.org>
[mailto:re-wrenches-boun...@lists.re-wrenches.org
<mailto:re-wrenches-boun...@lists.re-wrenches.org>] *On Behalf Of
*Mark Westbrock
*Sent:* Friday, May 07, 2010 10:33 AM
*To:* RE-wrenches
*Subject:* Re: [RE-wrenches] Enphase performance
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.
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.
Screen shot of a day's power production of 22 M190 microinverters
(nominal 4180 watts AC):
*Error! Filename not specified.*
Mark
Mark Westbrock
NABCEP Certified Solar PV Installer
NM ER-1J Journeyman Electrician
Positive Energy, Inc.
office: 575-524-2030
cell: 575-640-2432
westbr...@positiveenergysolar.com <mailto:westbr...@positiveenergysolar.com>
www.positiveenergysolar.com <http://www.positiveenergysolar.com>
We definitely experienced an overstatement.
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.
Randy
Kirpal Khalsa wrote:
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.
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.
--
Sunny Regards,
Kirpal Khalsa
NABCEP Certified Solar PV Installer
Renewable Energy Systems
www.oregonsolarworks.com <http://www.oregonsolarworks.com>
541-218-0201 m
541-592-3958 o
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