Version 8: Tracker Diffuse Shading Definition: All Trackers VS Central Tracker

[Lance McGrew]

Hello,

We are curious as to how the All-Trackers Option in the Diffuse Shading Definition is calculated. Is it taking each individual tracker and calculating the shade as an average amongst the totality of the site? or is there another method. 

We are working on a site that has some segregated areas that may not experience as much shade compared to the center of our larger rectangular area.  in this instance what choice would be the most appropriate? 

The site is 440 MW. 

We have done multiple runs:

•  version 7 we obtained = 1647 specific yield
• Version 8 All Trackers = 1587 specific yield 
• Version 8 Center Tracker = 1633 specific yield 

Using the center tracker, brings us closer to the Version 7 yield however does that that equate to a more accurate and viable choice, or does the significant drop to 1587 provide a more accurate representation of our site. 

[Michele Oliosi]

Hi,

Yes, indeed, the “All trackers” option will average the shading factor tables on all the trackers in your scene. This is evaluated at 7 different tracker angles, integrated over sky directions, and then interpolation profiles are then generated. In the end, you have a profile that takes in a tracker angle and gets out a shading factor for the diffuse and albedo components.

In general, the best is to use the “All trackers” option. Since it takes the whole scene into account, it is the most representative. Besides, the “central tracker” may or may not choose the neighbors properly, i.e., it is good to check the selection automatically made by PVsyst when using this latter option. The only downside to the “All trackers” option, is the long calculation time at the “simulation initialization” stage.