Evergreen Solar Panels

72 Posts
Sep 21, 2008 09:36 am
Evergreen Solar Panels

I currently have two Evergreen 170w panels connected directly together in series.

Is it safe or appropriate to connect either:

- 1 or 2 Evergreen 180w panels in series with the current 170w

- 1 or 2 Evergreen 190w panels in series with the current 170w

- 1 or 2 Evergreen 195w panels in series with the current 170w

I think that they are all fully compatible, but wanted to make sure before investing.

thanks in advance for any advice.
220 Posts
Sep 21, 2008 03:32 pm
Re: Evergreen Solar Panels

 hi keith,

  from your recent posts i see you have some really great projects in the works. there is a real satisfaction that comes from planing out a system, putting it together and having it run as expected. even the debugging is fun if it does not run quite as expected.

  as far as those evergreen modules go- i just love them. i swear by the b module specs. i have some of the a's and some of the b's and i can't see any difference in them..one of the b modules i got a great deal on has a small scratch on the aluminum frame. but puts out exactly like the a spec modules.

  now, about adding on to your system.
 first off i see from your posts that you are running a xantrex xw controller in the roanoak area. your controller has an absolute max voc (volts open circuit) rating of 150vdc. the record low temp in Roanoke is -11*f. we will need these numbers latter.

 the mixing of modules is a hotly debated subject and there are both pros and cons to it. one advantage would be that you can just pop another module in while building up to your final system size, and it can be done. a disadvantage to this is that you limit your string current output to the lowest module specs in that string. ie running a 180 in a series string of two 170's would limit the imp (current max power) to that of the 170 module. moreover we increase our total voc to the combined total volts of all the modules in that series string. normally we think of this as a good thing while using an mppt controller. until we start getting close to the controllers max voc that is. this is where our low temp for our area comes into play. there in Roanoke it's -11*f and we have to go to nec 690.7 for our needed correction factor. i can't find a free link right now so i'll list the correction factors for the forums use.
                nec 2008, table 690.7
ambient temp *f    factor
76 to 68           1.02
67 to 59...........1.04
58 to 50           1.06
49 to 41...........1.08
40 to 32           1.10
31 to 23...........1.12
22 to 14           1.14
13 to 5............1.16
4 to -4            1.18
-5 to -13...........1.20
-14 to -22         1.21
-23 to -31.........1.23
-32 to -40         1.25

 here are the specs for those evergreen modules
 vmp (volts max power)
 imp (current max power)
 voc (volts open circuit)
 isc (current short circuit)
 current (amps)
es 170 watt is vmp 25.3 imp 6.70 voc 32.4 isc 7.55
es 180 watt is vmp 25.9 imp 6.95 voc 32.6 isc 7.78
es 190 watt is vmp 26.7 imp 7.12 voc 32.8 isc 8.05
es 195 very rare module, never seen one but listed as
es 195 watt is vmp 27.1 imp 7.20 voc 32.9 isc 8.15

 if we take for example a series string of two 170's and one 180 we get a string that acts like three 170's with a voc of 32.4 & 32.4 & 32.6 = 97.4 x 1.2 temp correction =117 voc. still in good shape with that xw's max rating of 140voc (operating max). now if we try to squeeze another 180 in we get 130 x 1.2 = 156voc corrected and bye bye controller. as an aside this has always bugged me.. we pay good money for a controller and then we have to derate it for an event that may or may not happen every couple of years. i suppose in a case like this you can dial in an extra 10% voltage drop for winter operations (an extra legnth of wire or something) but that should be built into the controller imho.

 so keith when you get up to four modules you have to start going with separate series strings. ie two 170's in series. and two 180's in series with the outputs paralleled at a fused pv combiner. then you could add on in twos. (another series string of two at a time). up to the max current output of the controller. your max input will be limited by the nominal voltage of your system. about 720 watts of pv @ 12vdc and about 1440 Watts of pv at 24vdc nominal. one good thing is these controllers are rated for continuous operations and don't need the duty cycle derating.

i do hope this helps more than it confuses you.

good luck.
« Last Edit: Sep 22, 2008 02:56 am by david ames »
72 Posts
Sep 21, 2008 04:16 pm
Re: Evergreen Solar Panels

Thanks for the excellent info.

I think I get it, mostly. :-)

So, to see if I'm understanding ...

In simple laymen's terms ... the string is limited by its weakest link.

If I were to get two 180w instead, then I could run them in parallel .. right from the get-go, and should still be safe on my mppt controller? Since I'm only going up to 16ish amps ...with little change in voltage?


But for now, I'm buying more than I can use, by getting a single 180w.

A shame, but ok. I really like buying american made, and the 170w panels I have ... have performed fairly well.

But, getting a 170w would be better. They are currently listed here as 'Call for Availability' ... and I think they are no longer manufactured, in favor of other 'sizes'.

Anyone know how to get one?

And a 'B' module has some minor defect ... right? Where can I find them?

« Last Edit: Sep 21, 2008 04:17 pm by Keith Birchfield »
220 Posts
Sep 22, 2008 12:50 am
Re: Evergreen Solar Panels

 sounds like we are good. i vote for adding another series string of the 180's.

  you are right about evergreen ending production on those modules. the entire sl line (made in usa) and the rl line(made in germany) are being replaced by the sl-ku line (made in usa) and rl-tu line (made in germany) these new modules are for (suitable)for the ungrounded pv systems that are becoming the world standard. don't anybody panic. we can still ground these new modules because we just love  driving copper rods into the ground here in the usa.

"In simple laymen's terms ... the string is limited by its weakest link."

  this is the case here with this example. but we should not get carried away mixing and matching. here we have the same family of module and fairly close imp's. with the same shape i/v curve. i have only gone up and down one module size (to keep imp close) while mixing this line of pv and always have predictable results. i would not consider mixing.. say a cigs module in with a polly. then again it might be interesting for fun? i guess what i mean is mixing of modules in series strings is possible however it might not be the best option but a very useful one when building a system over time with limited funds. that said- mix and match at your own risk.

 you can still find some of those "b" modules around. altE has had them from time to time. i don't see any here now but maybe give them a call and see.

the best of luck.
« Last Edit: Sep 22, 2008 03:14 am by david ames »
578 Posts
Sep 22, 2008 10:48 am
Re: Evergreen Solar Panels

hi guys, generally in colder climates, the most 18v modules you can put on an open format mppt controller will be 3 in series, and anywhere from up to 5 or 6 stings depending on the controller.

as far as mixing modules, normally you would not do it.  since these are all essentially the same model or "brothers" you would try to get as close as possible to what you have, so as not to throw off the IV curve for the mppt function.  so 170s and 180s together not a big deal, 170s and 195, will certainly be functional but not the most optimal.

 availability may drive this decision as well.  with the tax credits not being renewed, the market is the craziest i have ever seen it, in terms of supply available to meet the demand.  all installs must be done before jan 1, so installers big and small are buying up everything they can to be eligible for rebates on systems. 

info literally changes daily, so if you or anyone else needs modules, call our staff and we would be glad to help .


altE staff

"Making Renewable Do-able"

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
72 Posts
Sep 22, 2008 09:00 pm
Re: Evergreen Solar Panels

Thank James and David.

I've got a single 180w ordered to top off my 170s. :-)

That should complete my solar electric project for now ... time to focus on solar thermal for a bit.


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