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

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

Vasco Zeferina gravatar image

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.

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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.

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

MJWitte gravatar image 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 gravatar image 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 gravatar image MJWitte  ( 2018-08-30 16:50:37 -0500 )edit

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

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Last updated: Aug 23 '18