[EnergyPlus_Support] Re: Solar Angles Calculations

[EnergyPlus_Support-owner@xxxxxxxxxxxxxxx]

As Brent said before, the program uses the "average" of the solar position for the number of days shown in the ShadowCalculations object (default - 20 days).

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, saleh saadi <salehsnjsaadi404@...> wrote:
>
> Thanks Brent. 
> It matches perfectly. 
> 
> If the user doesn't change the default values from 20 to say 1, then E+ will use the average values Or E+ internally calculates the solar angles based on time steps. 
> 
> regards,
> Saleh 
> 
> 
> 
> ________________________________
>  From: "Griffith, Brent" <brent.griffith@...>
> To: "EnergyPlus_Support@xxxxxxxxxxxxxxx" <EnergyPlus_Support@xxxxxxxxxxxxxxx> 
> Sent: Wednesday, October 24, 2012 9:51 AM
> Subject: RE: [EnergyPlus_Support] Solar Angles Calculations
>  
> 
> Â  
> 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. 
> Â 
> From:EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of saleh saadi
> Sent: Tuesday, October 23, 2012 7:18 PM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Solar Angles Calculations
> Â 
> Â  
> Hello Everyone, 
> Â 
> 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.  
> Â 
> For 1hr time step: 
> 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? 
> Â 
> thanks, 
> Saleh
>




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