RE: [EnergyPlus_Support] Re: Daylighting in Energy Plus

Daylighting dimming controls for the Lights object are activated by setting the - Fraction Replaceable field to
1. Setting the field to 0 turns off the dimming controls.
!- =========
Lights,
Office Lights 1, !- Name
Main Office, !- Zone Name
Office Lights Schedule, !- Schedule Name
LightingLevel, !- Design Level calculation method
1039.706, ,, !- Lighting Level {W}
0.0, !- Return Air Fraction
0.35, !- Fraction Radiant
0.25, !- Fraction Visible
1.0, !- Fraction Replaceable -- activates dimming control by DAYLIGHTING objects
Ambient Lighting; !- End-Use Subcategory

Daylighting:Controls
In this method daylighting illuminance levels are calculated and then used to determine how much the electric lighting can be reduced. The daylight illuminance level in a zone depends on many factors, including sky condition; sun position; calculation point; location, size, and glass transmittance of windows; window shading devices; and reflectance of interior surfaces. Reduction of electric lighting depends on daylight illuminance level, illuminance set point, fraction of zone controlled and type of lighting control.
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After the simulation, you can display the following variables to show you the lighting levels at various time of the day.

You sould read the manual to find out more.
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Zone,Average,Exterior Beam Normal Illuminance [lux]
Zone,Average,Exterior Horizontal Beam Illuminance [lux]
Zone,Average,Exterior Horizontal Illuminance From Sky [lux]
Zone,Average,Luminous Efficacy of Beam Solar Radiation [lum/W]
Zone,Average,Luminous Efficacy of Sky Diffuse Solar Radiation [lum/W]
Zone,Average,Sky Clearness for Daylighting Calculation []
Zone,Average,Sky Brightness for Daylighting Calculation []
Surface,Average,Daylight Luminance of Window As Viewed From Ref Point 1 [cd/m2]
Surface,Average,Daylight Illum at Ref Point 1 from Window [lux]
Zone,Average,Daylight Illum at Ref Point 1 [lux]
Zone,Average,Glare Index at Ref Point 1 []
Zone,Sum,Time Exceeding Glare Index Setpoint at Ref Point 1 [hr]
Zone,Sum,Time Exceeding Daylight Illuminance Setpoint at Ref Point 1 [hr]
Surface,Average,Daylight Luminance of Window As Viewed From Ref Point 2 [cd/m2]
Surface,Average,Daylight Illum at Ref Point 2 from Window [lux]
Zone,Average,Daylight Illum at Ref Point 2 [lux], if applicable
Zone,Average,Glare Index at Ref Point 2 [], if applicable
Zone,Sum,Time Exceeding Glare Index Setpoint at Ref Point 2 [hr]
Zone,Sum,Time Exceeding Daylight Illuminance Setpoint at Ref Point 2 [hr]
Zone,Average,Ltg Power Multiplier from Daylighting []

The manual also show you how to define the reference points, effect of external and internal windows, and sky lights, etc.

The report on power consumption by the lights will show you the energy saved.

Dear Dr. Li,

For the second question, For the building lighting energy consumption requirement, can it be directly linked to daylighting calculation? for example if the zone aquires a little amount of natural lighting from the window. Can Energy plus tell me how much do I need of artificial lighting or energy to compensate that loss in natural daylighting?

How can Daylighting simulation show how much energy can be saved using the light from the window?

Thank you very much

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