inverter shoot-out at high noon [RE-wrenches]

Sun Mar 28 10:54:07 PST 2004

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Henry asked me to post the below on his behalf.

Bill Brooks wrote at 06:27 PM 03/26/2004:

>Chris and Joel,
>
>I can't remember what modules Mr. Cutler had on his house, but a 5% increase
>is a little hard to believe even with the worst mismatch in modules. I'm
>sure some manufacturers are worse than others, but I would be careful about
>throwing around those kinds of numbers without a little better
>substantiation.

Gentleman, 

It was nice to see my new work being mentioned By Chris F about my panel matching in my newest system. 

In my latest system , I purchased (36) , new photowatt 155 Si modules for 2.47 watt. These were "seconds" but who cares , a watt is a watt. The -155s ranged for a low of 146 watt to a high of 179 watts. I current matched the strings , in most cases within 1 watt , since I'm using a nominal 48 volt array. The 5% number is if the exact same panels were to be used with a long series HV string ,like for a sunnyboy , I'd lose the gain panel matching has.

The Photowatts came with individual curve trace from the solar-simulator at the factory. Btw my  almost 2X the cost Kyocera didn't. The panels have tolerances of -3/+5% for the TIGHT tolerance ones , what you put on your customers arrays , who knows , how does one tell ?

The entire issue of focusing on Peak or Rebate efficiency numbers as the metric for good performing solar systems is very misleading. I realize I am NOT the first person to come across current matching of panels , and in dollars , the solar panels are the ones getting the free ride so to speak. The Bottom line IMHO is what a system cost to how much power it generates.

So if I'm not the first , can someone please point me to where and installer finds this out ? does the new solar installer certification even talk about panel matching ?. What about the DIY crowd ? . I feel the need to get the word out , in a similar way to the drive I had for the HP91 article , that high voltage strings have a  cost , and that is your totally at the mercy of the panel manufactures in how your shinny red box will perform (John B , by the way where is my royalty check for the sunny breeze name :).. At least with 48 volt strings (Suntie/Outback/M5) you have options to over come the panel variances.

FYI , the Suntie GP/UPG on my Kyocera arrays were with 1-2% when I finished my work over a year ago even though the inverters have a 3-4% efficiency difference. On this photowatt array , the Suntie would be ahead by 3%, and if John wants to send another box , I'll run the test to prove it

I think using solar panels to verify inverters is the wrong approach , there are to many variables.  I agree that a solar simulator (pc controlled power supply) is the most likely short term solution , but who is going to pay for this 50K piece of specialized hardware and who will verify the tester ?

I think the use of low voltage strings will make a come back , why ? because bottom line is the owner/installer can control the factors to maximize the system's performance. Once you own the panel , they are what they are ... With 48 volts , you can use bigger wire and match the panels to offset any raw efficiency differences (were talking 4% from worse to best on all the CA listed inverters) 

There should be more focus on system performance , and before you blow this off and think , well My panels are premium , they will be closely matched , think about this , Every wonder why there are 15 different CPU speeds for sale ..... all the same chip ?? , its all about Si Manufacturing process  , if Intel can't make it 100% the same , what chances do the panels guy have

As Chris mentioned , Under Contract , I redesign the Suntie and yes I believe it is an outstanding product now ... I have invested a year of my life in making it perform flawlessly , reliably and in temperature extremes. Xantrex , Due to the HP article as seen the sales basically die of and it really is a shame since the product I reviewed has little in common with the GP/UPG

<http://www.solar-guppy.com/forum>www.solar-guppy.com/forum if you want to continue this discussion as I don't have posting ability to this list.

Henry Cutler 

Michael Welch

------------------------
"All power rests on hierarchy: an army is nothing but a well-organized lynch mob."
			Edward Abbey

Michael Welch, michael.welch at homepower.com
     Home Power magazine
     www.homepower.com
     To reach me: 707-822-7884
     To reach Home Power: 800-707-6585

===========================================================
**** Bounces like rubber! Shatters like ceramic! ****
Discover Crazy Aaron's Thinking Putty in grown up 
handfuls. It's the creativity unleashing, mood enhancing 
desk toy!
http://click.topica.com/caab4CEbz8Qcsbz9JC9f/ Crazy Aaron Enterprises
===========================================================

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