In the ShadowCalculations object, you can control the frequency of the solar angle calculations. For something like this you will want to set it to 1 day. The default is 20 days, so the solar angles are an average for a 20 day period of time.
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of saleh saadi
Sent: Tuesday, October 23, 2012 7:18 PM
Subject: [EnergyPlus_Support] Solar Angles
I'm trying to understand how E+ calculates the solar angles such as incident angles on tilted surfaces (or simply for vertical surface). I have used correlations in Duffie and Beckman Book " Solar engineering of thermal process" to calculate the solar angles. I extracted data of cos of incident angles from E+ (output: Surface Ext Solar Beam Cosine Of Incidence Angle) and compare the two results. For some
days, the values are matching but for others they are off . For this exercise, I have used a vertical south wall with no shading, and no windows.
Does E+ calculates the solar angles at the end of the time step or at mid point of time step? or averaged over some points in a time step?