When looking at the various systems we have installed with different module/inverter combinations its hard to make a perfect performance comparison as tilt, orientation, module, and degree of transient shade vary considerably. Additionally many string inverters we have out there do not have web monitoring, and a number of M190 based systems have had numerous failures so they are not good for comparison either. That said, I did do a quick comparison of 4 systems that are about the same age, have the same tilt, orientation and are all shade free. The kWh/kW for 2012 are listed below:
M190/Sharp240 1,336 kWh/kW M215/Sharp240 1,488 M215/SW245 1,411 SB5000/Sharp235 1,468 It seems the upper limit of Enphases recommended module wattage may be a little high for the Midwest, but its hard to say what will happen over the lifetime of the system as the module degrades. Previous to installation I suspected the 240 was a little oversized for the M190, but price decreases at the time allowed us to keep our installed price and give the customer a larger system. Pricing aside, I would likely not do it again unless there was an AC limitation, or non-ideal module orientation. Garrison Riegel Solar Service Inc [p] 847-677-0950 <http://www.solarserviceinc.com/> www.solarserviceinc.com NABCEP Certified Solar PV and Thermal Installer From: [email protected] [mailto:[email protected]] On Behalf Of Jason Szumlanski Sent: Monday, January 28, 2013 7:30 AM To: RE-wrenches Subject: Re: [RE-wrenches] high insolation value and inverter undersizing I found the latest module "rightsizing" paper by Enphase pretty interesting. It does stand to reason that there are a lot of hours in the day where the inverter is producing less than rated power, so increasing the module size makes sense. Obviously there is an optimum point in every system where clipping exceeds gains, but that's virtually impossible to nail down due to so many factors being involved. I think the point would be that PV mods are coming down in price so much that "rightsizing" is basically equivalent to "upsizing," within reason, of course. Spending an extra 25% on PV might increase the installed system cost by 5-10%. Jason Szumlanski Fafco Solar On Sun, Jan 27, 2013 at 6:00 PM, Marco Mangelsdorf <[email protected]> wrote: I have had a concern for a long time that as PV modules have gone up in output that there is inevitably going to be more and more clipping taking place as theyre paired with comparatively lower output inverters. In effect, matching, say. a 260-watt module with a micro inverter with a max output of 225 watts reduces that 260-watt mod to 225 watts. Its not a matter of if clipping will take place, but how much and how much actual harvestable energy will be lost. Out here in the tropics, even in January with the lower sun angle, we see irradiance levels well above 1,000 watts/square meter range. Take a look at what I copied today from a weather station that we installed at nearby installation. Given the clipping issue inherent in using undersized inverters, it seems to me that moving to larger output micros makes a whole lotta sense. Ive got one of the first installs using the Power-One 250-watt and 300-watt micros and am so far quite impressed. Why use a 225-watt rated micro with a 225-watt or higher output mod when larger micros are now readily available? What are the views out there regarding this clipping issue? Is it as minimal as our Enphase friends suggest in their latest white paper or more of an issue as I conclude? marco Environmentals from Weather Station at a Hilo, Hawaii installation Sunday, January 27th 2013, 12:40:00 pm Ambient Temp. 25.30 °C Cell Temp. 41.70 °C Insolation 127.81 kWh/m² Irradiance 1,175.00 W/m²
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