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

Incident solar diffuse radiation on the floor

asked 2018-09-06 07:26:43 -0600

taher.ahel gravatar image

Is there any way to find out the amount transmitted solar diffuse radiation on the floor? or total radiation incident on the floor? energyplus has this output for beam radiation:

Surface Inside Face Exterior Windows Incident Beam Solar Radiation Rate per Area

but I cant find same thing for incident solar diffuse radiation on the floor or total incident solar radiation on the floor.

the Surface Inside Face Initial Transmitted Diffuse Absorbed Solar Radiation Rate calculate solar diffuse radiation absorbed by floor and that isn't my point.

Sincerely Taher

edit retag flag offensive close merge delete

1 Answer

Sort by ยป oldest newest most voted

answered 2018-09-06 14:10:49 -0600

Surface Inside Face Solar Radiation Heat Gain Rate
Surface Inside Face Solar Radiation Heat Gain Rate per Area
Surface Inside Face Solar Radiation Heat Gain Energy,hourly
edit flag offensive delete link more


Oh, but you said "incident", these are what's absorbed. So, you could just divide these by the floor surface solar absorptance. The problem with the diffuse is that there's the initial diffuse from the windows, but then there's diffuse reflections from all surfaces in the zone. The algorithm tracks what's absorbed but never really adds up the incident diffuse.

MJWitte gravatar imageMJWitte ( 2018-09-06 14:15:58 -0600 )edit

Yes E+ never adds up the incident diffuse... also I cant divide above output by floor surface solar absorptance because of the fact that E+ calculate it in different and a bit complex way. May I suppose all transmitted diffuse solar radiation will fall on the floor? Is consequent error big? My zone is a greenhouse with 4080 m2 floor area and 6m height. all surface are glass.

taher.ahel gravatar imagetaher.ahel ( 2018-09-11 10:29:50 -0600 )edit

No, you cannot assume that all transmitted diffuse solar will fall on the floor. The entering diffuse from any given window is distributed by area to all other surfaces in the zone (including other windows) except for surfaces facing in the same direction. For example,the diffuse entering through a south-facing window will not cast any diffuse on other south-facing surfaces.

However, it is true that Surface Inside Face Initial Transmitted Diffuse Absorbed Solar Radiation Rate divided by the surface solar absorptance is equal to the initial incident diffuse before allowing for reflections.

MJWitte gravatar imageMJWitte ( 2018-09-11 13:15:00 -0600 )edit

That's completely true. I set solar absorptance to 0.9999 then I sum beam and absorbed diffuse and compare it with above way, the answer was same. Thank you

taher.ahel gravatar imagetaher.ahel ( 2018-09-11 15:03:02 -0600 )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

1 follower


Asked: 2018-09-06 07:26:43 -0600

Seen: 108 times

Last updated: Sep 06 '18