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# Natural and artificial lighting [lux]

Hi!

I'm working on an outdoor lighting project. Previously, I've worked on other projects calibrating energy models using EnergyPlus and jEPlus, and I'm currently trying to find a way to obtain a dynamic and relatively calibrated model to predict how much artificial lighting I need to use, in addition to natural lighting, to meet the conditions of my outdoor area.

Through my experimentation, I've found that by using the Daylighting: Controls and Daylighting: ReferencePoint objects in EnergyPlus, I can determine how much to reduce the power of the artificial lighting based on the natural lighting that reaches the sensor in order to meet the conditions I've specified. However, I cannot obtain the lux produced by the artificial lighting as a result.

I've also tried other simulation programs such as Dialux, but in this case, I only get the information I need during the day since it does not combine natural and artificial lighting for outdoor areas at night.

Do you have any ideas on how to calculate the lux produced by artificial lighting at night in EnergyPlus?

Thank you for your attention. Regards.

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One option I can think of is

1. Prepare two models: The model A has artificial lighting with daylighting control (Daylighting:Controls and Daylighting:ReferencePoint). The model B does not have articial lighting (i.e. change the lighting level in the model A to 0W).
2. You can obtain the Lux at the Daylighting Reference Points for both the model A and the model B by Output:Variable Daylighting Reference Point 1 Illuminance, Daylighting Reference Point 2 Illuminance, Daylighting Reference Point 3 Illuminance...
3. The Output:Variable of the model A is the Lux for artificial lighting + the natural lighting at the Daylighting Rontrol Points. The Output:Variable of the model B is the Lux for the natural lighting only at the Daylighting Reference Points. So, you can calculate the Lux of artifical lighting only at the Daylighting Control Points.

Lux of artifical lighting only = (Lux of artifical lighting + natural lighting) - (Lux of natural lighting)

i.e.

Lux of artifical lighting only at Daylighting Reference Point 1 = (Daylighting Reference Point 1 Illuminance of the model A) - (Daylighting Reference Point 1 Illuminance of the model B)

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