kjs55 Posted October 14, 2019 Share Posted October 14, 2019 (edited) PVsyst v6.84: I am importing measured irradiance data from a tilted global POA pyranometer (GlobInc aka GPI). I would expect Mod GlobInc to exactly align with the Mes GlobInc that I am importing; however, this is not the case.The first measured GlobInc value is 446.7 W/m^2. Upon importing, I look at the modeled GlobInc value at the same timestamp. GlobInc (Hay model) for the same tilt and azimuth is 416.0 W/m^2. So, there is a 7% deviation b/w Mes and Mod GlobInc at this timestamp (at times the deviations are larger than 7%).The deviations are notably larger at the edges of the day (morning/afternoon) compared to around solar noon.I have set PVsyst to use the Hay transposition model per the following post:https://forum.pvsyst.com/viewtopic.php?t=40/Another note: For both Hay and Perez, it reports albedo = 0.2 for GlobInc; however, there is no option to define albedo when importing custom measured irradiance. Should albedo be a user input to the custom data import tool? Edited December 16, 2019 by kjs55 Link to comment Share on other sites More sharing options...
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