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

asked 2014-11-10 07:10:44 -0600

hema gravatar image

updated 2017-05-04 08:54:06 -0600

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:

  1. Role of daylight controls in open studio?
  2. 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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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 gravatar image Benjamin  ( 2014-11-10 07:54:34 -0600 )edit

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

hema gravatar image hema  ( 2014-11-10 08:30:23 -0600 )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 gravatar image David Goldwasser  ( 2014-11-10 08:38:41 -0600 )edit

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answered 2014-11-10 08:52:43 -0600

updated 2014-11-11 23:09:03 -0600

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:

  1. 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
  2. The split flux algorithm used in EnergyPlus can be pretty inaccurate
  3. In Radiance, only one space per thermal zone can be calculated
  4. In Radiance, only the primary daylighting control is used for calculating the lighting load control
  5. Despite the limitations of the current Radiance implementation, this is the best way in OpenStudio to derive the daylight metrics.
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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 gravatar image macumber  ( 2014-11-10 10:00:27 -0600 )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 gravatar image rpg777  ( 2014-11-10 10:34:09 -0600 )edit

answered 2014-11-10 08:28:57 -0600

updated 2014-11-10 08:34:03 -0600

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.

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So, for 18 m x 12 m, i ll have only 2 daylight control?

hema gravatar image hema  ( 2014-11-10 08:47:03 -0600 )edit

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Asked: 2014-11-10 07:10:44 -0600

Seen: 1,527 times

Last updated: Nov 12 '14