Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question

Mismatch between Transmitted Solar rate and sum of solar radiation gains in EnergyPlus

asked 2018-08-22 11:56:58 -0500

Vasco Zeferina's avatar

I'm new to EnergyPlus modelling and I'm trying to analyse the hourly energy/load balances of my single room model.

In my energy balance, there is a mismatch between Zone Windows Total Transmitted Solar Radiation Rate W and the sum of all (Opaque surfaces) Surface Inside Face Solar Radiation Heat Gain Rate W (Transmission rate being higher)

Can you explain me the mismatch of this Heat balance? What heat load is missing to close the balance? Is it the sum of all Surface Window Shortwave from Zone Back Out Window Heat Transfer Rate of my windows?

Thanks in advance.

edit retag flag offensive close merge delete

1 Answer

Sort by ยป oldest newest most voted

answered 2018-08-23 14:48:33 -0500

If you set the inside material layers of the zone surfaces to have Absorption Solar = 1.0, then your balance should match. With typical values of 0.9, then some of the solar is reflected diffusely around the room, and some of that will go back out the window(s). So, yes, I would expect the sum of Surface Window Shortwave from Zone Back Out Window Heat Transfer Rate to make up the difference (assuming there are no Lights in the zone, because this value includes visible energy from Lights which is transmitted out the window). If you haven't found this yet, the Input Output Reference contains definitions of all of the output variables. Just search for the variable name.

edit flag offensive delete link more


Meant to say "Solar Absorptance = 1.0".and typical values of 0.5-0.8.

MJWitte's avatar MJWitte  ( 2018-08-23 14:49:22 -0500 )edit

The definition of Surface Window Shortwave from Zone Back Out Window Heat Transfer Rate is clear about you were saying, "short-wave radiation heat transfer from the zone back out the window in watts. This is a measure of the diffuse short-wave light (from reflected solar and electric lighting) that leave the zone through the window". However, The sum of these surface flows didn't make up the existing difference (to clarify my model has no SW electric lighting gain). Therefore, there should be other heat flows components that i am not considering.

Vasco Zeferina's avatar Vasco Zeferina  ( 2018-08-29 09:38:36 -0500 )edit

If you dig enough and add output variables, and be sure to report at the timestep frequency, you should be able to sort this out. If not, you'll need to post the idf file.

MJWitte's avatar MJWitte  ( 2018-08-30 16:50:37 -0500 )edit

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Question Tools



Asked: 2018-08-22 11:56:58 -0500

Seen: 352 times

Last updated: Aug 23 '18