Different global incident in coll. plane with the same meteo data

[Mkitay123]

Hi everyone,

I am currently updating an old project using single axis trackers previously simulated with the version 7.4.4. 

The only change in the simulation was the PV modules which led to a 0.004% reduction in the plant capacity. 

The meteo file remained the same as the initial simulation with the version 7.4.4. So has the tracking parameters (tracking range, pitch etc)

I noticed however, that the global incident in coll. plane has reduced by 2.3% (from 2,263.4 kWh/m2 to 2,211.9 kWh/m2).

 

Has there been any updates to the transposition algorithm in PVSYST since the 7.4.4 version that could justify the changes? 

What could be the reasons for the drop?

 

I appreciate any input to understand the root cause of the shortfall.

 

 

 

[Agnes Bridel]

Few corrections or improvement have been implemented since version 7.4.4 and it is difficult to give an explanation on the discrepancy without more details. In general, there were no changes made in the transposition algorithm, but this could be related to some improvements made in terms of azimuth and tilt definition for tracker axes. please feel free to share your project at support@pvsyst.com so that we can take a closer look. 

 

Best, 

[Mkitay123]

Hi Agnes,

 

Thank you for your quick response. 

I noticed that the pitch in the orientation tab has changed. I understand the the pitch stated in the orientation tab is captured from the shading scene. The shading scene has 5 different pitches from (9.5m, 10.5m, 11m, 11.5m, 12m), could you please clarify how PVSYST calculates the pitch assumed in the orientation part? 

IS the pitch in the orientation used for the calculation of the global incident on coll plane? or is it calculated from the shading scene?

Figure below for the initial simulation with PVSYST 7.4.4

Figure below on latest simulation PVSYST 7.4.8

 

 

Also, is the global incident on coll. plane calculated based on the parameters in the orientation (tracking range, backtracking, pitch etc)? How is the impact of backtracking and shading losses accounted for in the overall POA?

 

 

Edited August 20 by Mkitay123

[dtarin]

Your GCR has increased in the new simulation, which will result in a lower transposition factor. In the shading scene under backtracking management, the pitch used for POA calculation and backtracking is selected, either automatically or specifically by user. POA (GlobInc) doesnt not consider shading losses, GlobEff does.