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

Incidence angle in EnergyPlus

asked 2016-10-06 04:00:46 -0500

it's avatar

updated 2016-10-06 19:35:35 -0500

I am wondering how EnergyPlus takes incidence angle into account when it calculate solar radiation transmittance from outdoor to indoor. I would believe that there is a different solar heat gain coefficient when solar radiation strikes a glazing pane at noon and afternoon. SHGC in noon could be higher than one in afternoon. Because WINDOW developed by LNBL can show this phenomenon, EnergyPlus could consider SHGC varied in time. Is there information about a calculation method for incidence angle ? In addition, is a calculation method able to consider incidence angle for both a transparent glazing and a translucent glazing?

Your comments are appreciated.

Regards, IT

edit retag flag offensive close merge delete

1 Answer

Sort by ยป oldest newest most voted

answered 2016-10-06 11:59:21 -0500

Archmage's avatar

SHGC is a specific metric for window performance, but it is not something that EnergyPlus ever uses directly during a simulation. EnergyPlus will report out a value for center-of-glass SHGC based on the window description, but that is for a special case used for standard reporting with direct normal incidence and fixed thermal boundary conditions. As you say, a real time SHGC, were such a report available, would vary over time with incidence angle as well as the thermal conditions surrounding the window. EnergyPlus already does take this into account.

There is a section in the Engineering Reference called Calculation of Angular Properties that describes how angle of incidence is handled for window performance.

The WindowMaterial:SimpleGlazingSystem has an SHGC input, but it is used by a model that then constructs a more detailed representation of the window, with a different angular model (see table Normalized Transmittance Correlations for Angular Performance), and it would also have a time-varying "SHGC."

edit flag offensive delete link more

Your Answer

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

Add Answer

Training Workshops


Question Tools



Asked: 2016-10-06 04:00:46 -0500

Seen: 902 times

Last updated: Sep 29 '21