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RE: [EnergyPlus_Support] Energy Plus vs TRNSYS





The window “properties” may be the same on input but these are characterized for normal incidence.  However in energy modeling, windows rarely experience the sun shining at right angles to the window.  I suspect the two programs differ in how they model transmission at higher incidence angles.

 


From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Brouchery Herve
Sent: Wednesday, July 21, 2010 8:07 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Energy Plus vs TRNSYS

 

Hello,

New to Energy Plus, I learn how to use the software by simulating a basic building (parallelepiped with windows and internal gains). I use HVAC template HVACTemplate:Zone:IdealLoadsAirSystem to determine heating and cooling needs.

To confirm my simulation, I have a reference building simulation done under TRNSYS.

For the weather file, I have used the weather converter tool (provided by E+) to convert a .tm2 file into a .epw one.

My results show a big difference in the cooling need between the 2 simulators. After investigation, it appears that the zone solar transmitted energy results could be the reason for this difference. E+ computes around 15% more solar transmitted energy than TRNSYS.

As the windows characteristics are identical between both simulators, I am wondering if the weather files are really identical? How can we be sure that they are identical?

What should I check if the problem is not related to the weather files?

Many thanks for your help.
Herve



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