Revision history [back]

Correct, there are different models to apply to design day solar calculations. However, these are separate from the Solar Gains equation you shared for the annual simulation. The annual simulation uses solar radiation parameters set as weather data from the EPW (EnergyPlus weather) file, and you can read the EPW data dictionary to understand what weather variables are defined. It appears that the variables you asked about are:

• I_b, beam (direct) radiation - Direct Normal Radiation
• I_h, horizontal radiation - Global Horizontal Radiation
• I_g, ground-reflected diffuse radiation - there's not a direct EPW variable for this, but you could multiply the Diffuse Horizontal Radiation by the Albedo

For more information, there is a (very) thorough Unmet Hours post with diagrams on this topic as well.

Correct, there are different models to apply to design day solar calculations. However, these are separate from the Solar Gains equation you shared for the annual simulation. The annual simulation uses solar radiation parameters set as weather data from the EPW (EnergyPlus weather) file, and you can read the EPW data dictionary to understand what weather variables are defined. It appears that the variables you asked about are:

• I_b, beam (direct) radiation - Direct Normal Radiation
• I_h, horizontal radiation - Global Horizontal Radiation
• I_g, ground-reflected diffuse radiation - there's not a direct EPW variable for this, but you could multiply the Diffuse Horizontal Radiation by the Albedo

For more information, there is a (very) thorough Unmet Hours post with diagrams on this topic and another Unmet Hours post describing the design day solar calculations as well.