Global incident in Coll. plane decreases as Latitude gets closer to 0°

[Tharcisio Souza]

Hello, everyone. 

After running a few simulations on several sites of the Brazilian soil, I realized that the Global incident in Coll. plane from the Loss diagram was very different on each simulation. 

Since all of my simulations have fixed sheds, not trackers, I started wondering why in some cases I got over 6% Gain on Global incident in Coll. plane and others I got only 0.3%. Even if I used the optimization tool for tilt and azimuth enhancement, the Global incident in Coll. plane would not change significantly.

The only correlation I could find for this behavior was with the Latitude:  The closer I get to a 0° Longitude, the smaller the Global incident in Coll. plane is. This trend is clearly shown in the following table and scatter plot:

The column 'Gain' represents the Global incident in Coll. plane value taken from the simulation's Loss Diagram

 

For a visual reference of where those simulated plants are located: 

 

Given all that explanation, I have some questions:

1.  Is my interpretation correct and the closer I get to a 0° Latitude the smaller the gain for Global incident is? 
2.  Can you recommend me articles that explain this behavior, either on PVSyst or a more general sense?
3.  Why couldn't I get a significant enhancement of the Global incident in Coll. plane when I used the optimization tool (for tilt and azimuth)?

I hope you can help me with those questions, and I'm available for further discussions. 

Best regards.

 

[dtarin]

As you approach the equator, the sun is more directly over the modules. This is to be expected. Not only will the optimal tilt reduce as you move closer, but as you have identified, so will the transposition gain.