Backtracking in v1.15.2013

Thank you Paul,

The new improvements look great. I have downloaded the beta version and I will give you my feedback.

Tamir

Hi Paul,

I went through my test cases with the beta version of SAM as well as the new version of PVSYST (v6.10). In general there is very good agreement now between the two programs without having to do any massaging of the SAM data. There are slight differences arising from using different data sets for the weather data and the accounting of losses is slightly different (albedo, mismatch, etc). I did notice that PVSYST completely overhauled their tracking algorithm with respect to diffuse shading and I was very surprised to see that the benefit of higher tracking angles is much reduced. This is true for SAM as well so I'm not sure if you are accounting for this diffuse shading as well or not but the end result is the same. This result is a little discouraging to me personally but you can't argue with the math. It appears that even though at 50% GCR you can go up to 60 degrees ROM without direct shading you cannot avoid diffuse shading at the higher angles and thus your benefit in energy harvest drops from a 2-3% increase to about 1% in sunny areas and

Hi Tamir,

Thank you for taking the time to do that comparative analysis.

For now SAM is not accounting for diffuse shading in the backtracking algorithm, but we are working on that question now, and plan to make some enhancements based on the results to next year's version of SAM.

Thanks again for all of your helpful and detailed feedback.

Best regards,
Paul.