Solar Panel String Setup Question

[senoird]

I have 9 Hyundai 305 panels on a ground mount. Currently I them in 2 strings - 1 is 4 panels the other is 5 panels. Reason for this is in the morning the 4 panel string gets partial shading from the neighbors tree while in the 5 panels miss it and in the evening just the opposite from the other neighbors tree. I was thinking that by separating them like that it would suffer less than bringing down the whole setup in one string in the morning and evening shading event. Any of you guys with more experience have a thought on that? Am I looking it wrong and would be better off just doing one 9 panel string? The inverters are 6500s so the mppt is plenty good to handle the voltage of all 9.

 

[FilterGuy]

There are a lot of different opinions on this. Assuming the panels have bypass diodes, the old problem of a little shade taking out the whole string is greatly reduced. However, Since you have the two MPPTs on the 6500, I would keep the strings separate.

 

[BryceFreeman]

I agree with keep the strings seperate but shading will greatly reduce panel's performance. Have you thought about mounting the panels higher to avoid the trees? Like mounting them on the roof or tilt brackets.

 

[senoird]

The trees are in line east and west of the panels. Unfortunately it was the only place I could put them. They do get full sun from 9-3 so it's not that bad. Just wanted to verify my thinking was correct.

 

[Hedges]

So long as no panel gets a hard shadow while others in the string get full sun. Full current can overstress bypass diodes. Should be OK if only when sun hits at 45 degree or more oblique angle. 9-3 does sound like 45 degrees, so should be OK. You don't gain/lose much power beyond that anyway.

Series vs. parallel, check MPPT efficiency curves (if available) vs. wiring losses. The loss in yield is probably insignificant. The lost power causing heating in MPPT would impact electronics life, more significant. e.g. 96% vs 98% efficiency is 2x the power loss, 2x the temperature rise (unless fan kicking on make the response non-linear).