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
altE staff

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

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