solar panel placement

49 Posts
Jan 13, 2009 06:39 pm
solar panel placement

I have 9 208watt sharp panels. 6 face east on the garage roof and 3 face south because I have a steep roof there so it keeps the snow off in the winter, and they do get sun in the afternoon to evening. My question is because they are all in the same combiner box running to the outback controller will the 3 effect the 6 for efficiency in the summer.  Thanks,  Jim A.
 
28 Posts
Jan 14, 2009 07:44 am
Re: solar panel placement

I believe they will impact your production. The MPPT (maximum Power Point tracking) in the inverter will not work well with two different exposures. There are a couple of grid tie inverters out there that have dual MPPT inputs that would optimize each set of panels for their maximum output. In order to do that you would need to run two pairs of wires back to the inverter and land each bank of panels on different inputs.
 
578 Posts
Jan 14, 2009 02:41 pm
Re: solar panel placement

to james,

that will impact performance.  ideally it would be on two controllers as each set of modules has a different sun conditions simultaneously.

that being said, outback controllers are expensive, so barring the first solution, i think you did the best you could.

regarding the second post, you are on the right track if we are talking grid tie.  there are two practical issues though.  the only multi-mppt inverters i was aware of were the sharp sunvista (3) and the magnetek auruora (2).  both are extinct to the best of my knowledge.  the other issue is that while six might turn on an inverter, 3 in series (18v nominal) will not.

good discussion, these are fun.  i toyed with putting two arrays on a magnetek on my garage, but finances, laziness, and the thought of explaining what i had done to everyone got the best of me.

james
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49 Posts
Jan 14, 2009 06:43 pm
Re: solar panel placement

 thanks guys , I am off grid with a 48v system would this work with the 3 panels in series and a separate outback. I might add more later on the steep roof then.   thanks again
 
578 Posts
Jan 14, 2009 07:03 pm
Re: solar panel placement

yes, you can have 1 mx60 (or fm60 or fm80) on one array and another on the array facing a different direction.  you dont have to do it, but you should see some efficiency gains. 

you can have up to 5 strings on 3 in series on those outback controllers, so you have lots of room to grow.  if you cant find 208s anymore, the 216 and the 224 are the nearest brothers for adding on to your array.

cheers,

james
altE staff

AltE
"Making Renewable Do-able"
http://www.altEstore.com/

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
 
49 Posts
Jan 17, 2009 12:10 pm
Re: solar panel placement

  My father-in-law an electrical engineer and I were wondering
since the electricity generated can't back up into the other series of panels, how can you loose some efficiency on the ones in the sun?    thank you jim
 
578 Posts
Jan 17, 2009 12:44 pm
Re: solar panel placement

howdy,

i'll try to explain this to the best of my ability/knowledge.

what is happening is that the controller is tracking (the T in mppt) the incoming voltage.  ideally this works best when there is one I-V curve in place.  because in this example these multiple strings are hooked up to the same controller, this forces the controller to aggregate or take the mean voltage because it no longer has 1 I-V curve for the array but two.  the resulting new mpp is differnet than it would be with one array in the ideal setting.   

to the best of my understanding, this may not have a huge impact at say noon in summer, but at other times when the sun angle does matter the difference may add up to appreciable power and energy differences vs. the ideal (whole array of like and kind facing same way on one controller).

cheers,

james
altE staff

AltE
"Making Renewable Do-able"
http://www.altEstore.com/

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
 
49 Posts
Jan 17, 2009 06:12 pm
Re: solar panel placement

you are awesome in answering so quickly and your knowledge, thanks again Jim A.
 

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