Backtracking Low Angle Limit - For Glare

[Jackson White]

Hi, I need to model the yield considerations for limiting our backtracking angle to >20 degrees is there a way to do this in PVSyst?

For context, we need to do this to limit glare at times when the sun angle is very low. 
 

So instead of setting an upper limit to backtracking angle I am wanting to set a lower limit so that the panels do not get lower than 20degrees during low sun angle times. Is there a way of doing this that you are aware of?

[Michele Oliosi]

This is not simple, but let's see what we can do.

First, mutual shadings tend to happen starting with 20°- 30° angles of sun height. These are the times when backtracking is interesting, but also where it seems you are expecting glare. So you have a double constraint on these low sun angles.

Note that at times when backtracking is limited, you will have mutual shading. In these cases, it will be best to use just regular tracking. This is because backtracking is only convenient whenever you are removing most of the mutual shading (and electrical mismatch effects). So once you are in a mutual shading regime, I think it is probable that regular tracking will be best.

Based on that, you can run two simulations: one with backtracking and one without. For each of them, you can generate an hourly output file. Then you can process the data, and use the regular tracking one whenever the backtracking rotation angle would be < 20°. The resulting dataset can then be summarized to obtain yearly yields, etc.

[Jackson White]

Thank you Michele, I followed your suggestion and ran some processing in excel and it worked well. 

It would be interesting to see if limiting the rest angle for Backtracking makes it's way into pvsyst as it seems like this is becoming a common method for mitigating glare for roadways etc.