Why are there only two daylight controls in OpenStudio? What is the role of daylight controls?

I have a building having only ground floor 18 m x 12 m, I can place only two daylight controls which is not sufficient. I want to understand:

Role of daylight controls in open studio?
If i have to calculate lighting energy consumption, how will daylight controls help me If i place only 2 controls in large space?

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hema

asked 2014-11-10 07:10:44 -0500

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__AmirRoth__

updated 2017-05-04 08:54:06 -0500

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Was there a typo in the size of your space? Because I would think that two daylighting controls would be more than sufficient for a 12 m2 space.

Benjamin (2014-11-10 07:54:34 -0500) edit

Sorry for the typo..its 18 m x 12 m

hema (2014-11-10 08:30:23 -0500) edit

@hema if you retag as openstudio (one word) others will be able to find this post easier. You may also want to use existing daylighting tag.

David Goldwasser (2014-11-10 08:38:41 -0500) edit

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The daylighting controls are used to simulate, uh, daylighting controls, in an actual building. Therefore they need to be used judiciously, in spaces (and areas of those spaces) where it's anticipated there will be sufficient daylight to allow for electric lighting to be dimmed or switched off.

As David said there are two controls available per space as this emulates the "capability" of EnergyPlus. The typical use case for these things is the modeler will place one control near the perimeter and one deeper in the core, and set each control to "control" a percentage of the total electric lighting load in the space. In reality, there is one daylighting control (photosensor, what have you) in a given daylit area and the lighting is zoned and dimmed proportionally. The point is that daylighting controls as they are implemented in EnergyPlus and even OpenStudio at this point are fairly well divorced from reality. The OpenStudio team is planning to improve the daylighting control simulation modality, as are the folks at the CBEI. In the meantime you should be aware of these limitations:

In EnergyPlus, daylight transfer from one thermal zone to another is not possible with concave spaces, and even for convex ones the method is pretty weak
The split flux algorithm used in EnergyPlus can be pretty inaccurate
In Radiance, only one space per thermal zone can be calculated
In Radiance, only the primary daylighting control is used for calculating the lighting load control
Despite the limitations of the current Radiance implementation, this is the best way in OpenStudio to derive the daylight metrics.

rpg777

answered 2014-11-10 08:52:43 -0500, updated 2014-11-11 23:09:03 -0500

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If you are looking to get more information about the distribution of daylight within the space you are probably more interested in illuminance maps than daylighting controls, OpenStudio supports the EnergyPlus and Radiance simulation methodology for both of these. This video might be helpful.

macumber (2014-11-10 10:00:27 -0500) edit

This video has more detail about how to place the daylighting controls in a manner that actually relate to daylighting and glare analysis, and show how to use Radiance for the simulation in OpenStudio.

rpg777 (2014-11-10 10:34:09 -0500) edit

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OpenStudio daylighting control points are translated to Energy plus Daylighting:Controls objects. We matched EnergyPlus's limit of two per zone with two per space in OpenStudio. If you have multiple spaces in a zone with more than two controls, only two can be associated with the zone.

You still have to calculate the design load and typical usage schedule for your lights. Think of the daylighting controls as an override that turns them off or partially off when there is enough natural light.

If you have multiple thermal zones then you can have more than two daylighting controls.