One MPPT 2 strings with slightly different tilt.

[bendesa]

Hi All,

Most Grid Tied Commercial Inverters has multiple MPPT trackers. Each MPPT Tracker can be connected with 2 Strings.

What would be the disadvantage if we connect two strings (same PV Modules same number 18 x series) with slightly
difference in tilt?

The difference in tilt will not be more then 3 Degrees

What is your opinion about this?

Many thx in advance

Kind regards

Ben

 

[jaggedben]

It would be a disadvantage, but at the same azimuth and 3 degrees different tilt it would not be a be a very big disadvantage. My gut says the loss in production will not be more than 1%.

 

[bendesa]

It would be a disadvantage, but at the same azimuth and 3 degrees different tilt it would not be a be a very big disadvantage. My gut says the loss in production will not be more than 1%.

Thx for your reply,

That's what I'm also thinking. I can make some yield simulations in PVSyst to check the difference

Once again thx for your contribution

Regards

Ben

 

[GoldDigger]

The governing factor is that with the same number of modules in each string, and no partial shading, the output current will vary with tilt and the timing of that current will vary with azimuth, but to first approximation Vmp will be unchanged. That means that the MPPT algorithm would chose the same Vmp for both strings even if they went to separate inputs.
Partial shading, different between strings is the thing to avoid when combining to one MPPT input.
The second rule of thumb is that when, for whatever reason, two strings have different Vmp but within 5%, the power loss from paralleling them will still be less than 1%.

 

[Zee]

3 degrees difference? There will be no appreciable impact. Like 0.1%
3 degrees is so small I have that much in measuring error on the same roof!

Put another way I have ended up with 3 degrees difference on tilt racks on the same roof!

PS never go below 5 degrees or 1:12

( Off topic: Even split orientations have much less of an impact than previously thought. Even if 90 degrees apart, or 180 even.
(since matching V is key, V rises to near equivalent and constant values on both strings once any ambient light is present....and amps can differ wildly but not a big deal when in parallel)