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Hello, Does someone know where the difference between PVsyst and NREL's Solar Position Algorithm (SPA) comes from? I get an important difference in the incident angle between those models. SPA calculator : http://www.nrel.gov/midc/solpos/spa.html The parameters used : - Site location : latitude = 20.5°S ; longitude = 55.3°E ; elevation = 14 m ; time zone = UTC+4 ; No skyline nor shading - Pannel position : tilt = 0° ; azimuth = 0° (from north, negative toward east) - Simulation : start date = 01/01/1990 ,end date = 31/12/1990 - The meteorological data for PVsyst simulation comes from Meteonorm. Thus the label "12:00" should represent 12:30. Difference observed between the models : from +1° to +3° at sunrise (NREL - PVsyst) Changing the pannel position to : tilt = 2° ; azimuth = -135° (from north, negative toward east), I get : +3° to + 6° at sunride / +2° to + 3° before 12:00 / -2° to - 3° after 12:00 Based on the Beaminc (incident beam irradiation in the collector plane) calculation (BeamInc = BeamHor * sin Hsoli / sin Hsol), I assume the two models give very different results for the sun heigth on horizontal plane. Cheers, Sébastien

Thank you Bruno. Indeed, I thought the red dot was on the top of the collector (as it appears on the drawing on the left)!

Hello, PVsyst guide states : "In southern hemisphere, the plane azimuth is defined as the angle between north and collector plane.This angle is taken as negative toward east". However, if I put -135° in the "Orientation" pane (projet in the south hemisphere), I get a north-west orientation (instead of south-east). Should I believe the PVsyst guide or the drawing? Thanks in advance, Sébastien

Hi there, In the PVsyst 6 Help, I can find : - GlobIAM : Global on collectors, corrected for horizon, near shadings and IAM - GlobEff : "Effective" global, corrected for IAM and shadings simultaneously I don't get the difference between those two variables? Thanks in advance for your help Sebastien