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Number of Daylighting ReferencePoint

asked 2018-09-17 10:41:23 -0600

taher.ahel gravatar image

updated 2018-09-18 07:21:52 -0600

I have Large glass zone that is modeled in EnergyPlus, which contains dynamic shading so I must use SplitFlux method in order to calculate incident lux in specific reference point. SplitFlux method is just allowing using two Daylighting:ReferencePoint according to Engineering Reference: Daylighting Calculations

I have a large zone and I want to calculate lux in more points... Is there any way to add more ReferencePoint in SplitFlux method in order to calculate lux in all parts of my zone?


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It is possible to add more than 2 ReferencePoints but Energyplus only report reasonable Lux for ReferencePoint 1 & 2, the other ReferencePoints will be equal to zero Lux in the output then it's not acceptable.

taher.ahel gravatar image taher.ahel  ( 2018-09-18 07:30:42 -0600 )edit

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answered 2018-09-18 06:05:05 -0600

Since EnergyPlus 8.6.0, the Daylighting:Controls object is allowed to have as many Daylighting:ReferencePoint objects as you would like (see #5725) although recently we have uncovered some dangling limitations in the code that might limit some functionality (see #6889). I would recommend trying to use additional ReferencePoints and see if the results seem reasonable.

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I must use SplitFlux method. I've tried 10 ReferencePoint but I just see reasonable results in ReferencePoint 1 and ReferencePoint 2 but the other ReferencePoints have been reported equal to zero and I didn't face any severe error.

taher.ahel gravatar image taher.ahel  ( 2018-09-18 07:20:44 -0600 )edit

@JasonGlazer I'm seeing something similar - any more than 2 reference points, and it's illuminance output variable is always 0. My suspicion is that the WDAYIL and WBACLU arrays are sized to be 2x2, so they can't store any more info past 2 reference points. This is also mentioned in @MJWitte 's comment for your referenced "dangling limitations" pull request.

Aaron Boranian gravatar image Aaron Boranian  ( 2018-09-18 13:15:53 -0600 )edit

@Aaron Boranian So what must I do? really I'm not a developer.

taher.ahel gravatar image taher.ahel  ( 2018-09-20 08:06:46 -0600 )edit

I'm hoping to have this fixed for the 9.0 release coming out in a few weeks.

JasonGlazer gravatar image JasonGlazer  ( 2018-09-20 08:23:44 -0600 )edit
taher.ahel gravatar image taher.ahel  ( 2018-09-20 08:52:15 -0600 )edit

answered 2018-09-17 11:20:00 -0600

You can add an illuminance map, which is a uniform grid of points you can place across your zone; this will report illuminance in lux and save to the eplusout.sql file.

Unfortunately, you're constrained to rectilinear grids so you cannot reliably use this data for calculation of the typical daylight metrics (since it's not always possible to cover the entire floor plate with calculation points per LM-83 for example). Also, you cannot actually view that data in DView; you'll need to view the data in another tool. The old Results Viewer could view this data no problem, but, alas.

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Thank you But I want to control shading with the amount of Lux on the floor. Does illuminance map provide me the amount of Lux at Begin Timestep Before Predictor calling point? Because of the fact that I intend to use the amount of Lux in EMS. Daylighting ReferencePoint is appropriate but illuminance map is an output.

taher.ahel gravatar image taher.ahel  ( 2018-09-17 13:28:52 -0600 )edit

The illuminance map will provide daylight illuminance at the timesteps you request. I don't do EMS but I ASSume you can take the illuminance map values and use them as input to whatever you want to do in EMS -- that's kinda the nature of EMS, isn't it? Maybe an EMS expert can weigh in here.

rpg777 gravatar image rpg777  ( 2018-09-17 21:34:08 -0600 )edit

I can't reach illuminance map data in EMS... there is no sensor about there?

taher.ahel gravatar image taher.ahel  ( 2018-09-18 02:17:14 -0600 )edit

What I don't know about EMS could fill several volumes. Sounds like the added daylight reference points don't work (yet?), which is a bummer. Maybe someone here knows of a way to access the illuminance map data via EMS. If you use OpenStudio and the Radiance measure, you have more options, but that's a whole other rabbit hole you may not want to venture down (yet).

rpg777 gravatar image rpg777  ( 2018-09-18 10:34:37 -0600 )edit

Yes, the added daylight reference points don't work. Maybe I'd better split my zone to several thermal zone and set two reference points in each zone then connect splitted zones by AirFlowNetwork and interior opening windows then make opening windows always open.

taher.ahel gravatar image taher.ahel  ( 2018-09-18 12:55:38 -0600 )edit

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Asked: 2018-09-17 10:41:23 -0600

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Last updated: Sep 18 '18