bertin Posted August 21, 2014 Share Posted August 21, 2014 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.htmlThe 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 12:00Based 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 Link to comment Share on other sites More sharing options...
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