Hi all,

I'm trying to find out what the impact would be on the MPPT and/or Inverter if you have partial shade sometime during the day on some of the solar array? Is the entire string's generation forfeited? 
The reason I am asking is that although I don't see big palm tree shade currently on my intended north facing roof, I'm sure there will be some at some time during the year. 

It it better to have multiple MPPT's to negate this if it is an issue? And perhaps add some east and west panels as well?

Thanks

 

Edited May 8, 20197 yr by d3nominat0r

@d3nominat0r,

An MPPT / panel would be great but it is often impractical. This can be achieved by micro inverters  or dc optimisers or other bypassing hardware.

Even better, I see there has been recent mention of panels that have an MPPT equivalent instead of a bypass diode, but I have no experience with them.

It maybe that the costs outweigh the benefits or limit your future options, with high tech solutions.

So in general:

Shorter strings and more parallel strings can also be used to mitigate fixed shaded.

If during the productive part of a day it is known that fixed shade will travel and will be somewhere on a potential roof space. It might be worth considering an extra string over and above your MPPT power capability, say knowing that only 3/4 strings will ever produce simultaneously.

Because of the cell layout of a PV panel ( 3 long circuits down the long length of a panel), the panel orientation may also be used as a mitigating factor for  known shading.

In the sense that it is better to shade along the long length of a panel and affect 1 cell string than along the short length and affect all 3 cell strings.

There are half cell panel options now but I don't know if these are available locally.