[RE-wrenches] Enphase performance
Bill Loesch
solar1online at charter.net
Mon May 10 17:31:05 PDT 2010
Marv,
What would be a (or more) reason(s) that the module manufacturer wouldn't want to be on your approved list (and sell more modules)?
Thank you,
Bill Loesch
Solar 1 - Saint Louis Solar
----- Original Message -----
From: Marv Dargatz
To: RE-wrenches
Sent: Monday, May 10, 2010 4:59 PM
Subject: Re: [RE-wrenches] Enphase performance
Marco,
Sorry, I missed that question in the previous e-mail.
A couple of points about the compatibility list:
1. We include only modules that have passed our internal math check for compatibility over the temperature range of the inverter.
2. If the module manufacturer objects to being on the compatibility list, we will not include them.
Sunpower has objected, so they are not on the list.
Zhejiang Wanxiang Solar Co. Ltd is also shown as compatible with the M210.
The list is only a guideline. Any module that falls within the voltage spec over the expected operating temperature range of the installation, and does not exceed the inverter DC input short circuit current rating is certainly a valid combination, and the inverter is fully warranted. Notice that module power rating is not a factor here.
I hope this helps.
See ya!
Marv
707 763-4784 x7016
Marco Mangelsdorf wrote:
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! Marv707 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
dana at ecotechenergy.com
360.510.0433
On Mon, May 10, 2010 at 11:36 AM, Marco Mangelsdorf <marco at 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
dana at ecotechenergy.com
360.510.0433
On Fri, May 7, 2010 at 4:48 PM, Chris Worcester <chris at 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
chris at solarwindworks.com
"Proven Energy Solutions"
From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at 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 WestbrockNABCEP Certified Solar PV InstallerNM ER-1J Journeyman ElectricianPositive Energy, Inc.office: 575-524-2030cell: 575-640-2432westbrock at positiveenergysolar.comwww.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
541-218-0201 m
541-592-3958 o
----------------------------------------------------------------------------
_______________________________________________List sponsored by Home Power magazine List Address: RE-wrenches at lists.re-wrenches.org Options & settings:http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette:www.re-wrenches.org/etiquette.htm Check out participant bios:www.members.re-wrenches.org
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 9.0.819 / Virus Database: 271.1.1/2864 - Release Date: 05/09/10 08:26:00
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
----------------------------------------------------------------------------
_______________________________________________List sponsored by Home Power magazine List Address: RE-wrenches at lists.re-wrenches.org Options & settings:http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette:www.re-wrenches.org/etiquette.htm Check out participant bios:www.members.re-wrenches.org ----------------------------------------------------------------------------
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
------------------------------------------------------------------------------
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20100510/13395231/attachment-0003.html>
More information about the RE-wrenches
mailing list