I am modeling a building with many clerestory windows of various orientations in a complex roof geometry. I would like to accurately model the daylighting savings in eQUEST. Has anyone had luck creating an input function that uses daylight illuminance factors, as described by Steve Baker
Thanks,
Bill
William Bishop, PE, BEMP, BEAP, LEED AP
Bill,
Sorry, but I can't help you out on your daylighting question. I'm also sorry, but the song was AFTER my time. I'm more into 60's & 70's music and boogie woogie and piano blues artists who died 50 or more years ago. :)
Mike Busman
Bill,
Since eQUEST utilizes a split flux calculation which averages lighting levels, it is not super accurate when it comes to daylighting. You can, however, use daylighting to approximate energy savings in eQUEST using appropriately zoned perimeters spaces and sunspaces.
If you truly want accurate daylighting in eQUEST, you're going to have to use a third party software and create an 8760 schedule within eQuest to reflect the results (I suggest using a GUI for Radiance such as AGi32).
If I knew exactly what you were trying to do and had a better sense of the geometry you are working with, I could assist you further.
Unlike Mike, the song is BEFORE my time, but I'll spare you the old guy jokes ;)
Thanks,
David Griffin
David,
You can get a sense of the clerestory windows, curtain walls etc. in these views. Obviously, this will be fun geometry in eQUEST. The design team is also modeling it in IES-VE - I will see if they can get me their daylighting output for comparison.
[cid:image002.png at 01CE951E.DDF56ED0]
[cid:image003.png at 01CE951E.DDF56ED0]
~Bill
David,
Similar to John Aulbach, a frequent poster here, I started doing hourly simulations about 1982. That was when your input file had to be chiseled on a stone tablet. :)
Mike Busman
Michael R. Busman, CEM
Thanks Mike Andelman, John Aulbach, David Griffin, Umesh Atre and Liam Buckley for your helpful replies. For the benefit of the List, here's what I found out:
- DOE-2 input functions are not (currently) supported in eQUEST.
- DOE-2 and eQUEST use the split-flux algorithm to model internally-reflected daylight. The eQUEST daylight calculation works best when the illuminance at a reference point is due to light directly from the windows (not reflected from the interior).
- Available daylight tends to be overestimated when the reference point is near the back of the room (depth more than three times floor-to-ceiling height).
- The impact of split-flux method inaccuracies tends to be minor relative to total simulated building energy use.
- Contact Mike Busman if you have Fiat X1/9 questions or want your photo taken with a life-sized Big Bird.
Some reference material:" Fourth National Conference of IBPSA-USA, 2010.." Proceedings of the Ninth International Conference for Enhanced Building Operations, Austin, Texas, November 17 - 19, 2009.." Proceedings of the Solar 2007 Conference in Cleveland, 2007.
An, J. and Mason, S., "Integrating Advanced Daylight Analysis Into Building Energy Analysis
Kota, S. and Haberl, J., "Historical Survey of Daylighting Calculations Methods and Their Use in Energy Performance Simulations
Koti, R. and Addison, M., "An Assessment of Aiding DOE-2's Simplified Daylighting Method with DAYSIM's Daylight Illuminances
~Bill
Couple of suggestions:
1. Run the model in IES - I think they have a better daylight algorithm.
2. Use Daysim - you can get hourly light level readings from Daysim that you can postprocess to create a lighting schedule in eQUEST. This is probably fairly labor intensive.
Vikram Sami
The following article is a good read since it is related:
http://www.nrel.gov/sustainable_nrel/pdfs/47522.pdf. Some background info
is given with regard to the shortfalls of DOE2 daylighting vs backward
raytracing aka Radiance-based tools also, so I thought I'd post it for
reference. It also gives a good play-by-play in context of the NREL RSF
case study, which incorporated the use of SPOT, an Excel-based tool which
runs Radiance in the background.
That said, IESVE currently would fit better in your process obviously since
it's already being used in the project as you say. Similarly, as is
described for SPOT in the article, exporting a dimming schedule from IES is
simple from its Vista module once the simulation is done, and then imported
into eQuest. Apparently lots of other schedules were created during the RSF
design with software tools better suited for various analyses but the
central energy model was crunched by eQuest I believe using those imported
schedules. SPOT may still be of use as it is supposed to find the optimal
sensor placement, but any sensor placement will need to be consistent with
actual lighting layout/circuits anyways. Anyone familiar with SPOT might be
able to contribute.
Kent Beason
Felt like a response was warranted to clarify how this works.
There is no need to copy/paste from Vista or generate a separate schedule in IES VE. IES have a GUI for Radiance which allows the user to place a sensor in a zone, create a control algorithm for that sensor (more accurately, create a means for how the sensor should either dim or "step" lights on/off), run an annual daylight simulation using Radiance (for which we have an algorithm that looks at various sky conditions throughout the year and relates them to the sky conditions in the climate file), then, by means of simply ticking a box, feed the results of that annual daylight simulation directly into the thermal simulation.
It is true that you can export the actual hourly illuminance levels from Vista - but (again) there is no need to do that in order to use the results in the thermal simulation within the VE. In other words - it's not very labor intensive to actually incorporate an annual Radiance simulation into the thermal simulation.
That's the short version. If anyone is interested in learning more (as I don't wish to turn this into an IES thread), I'm sure you'll let me know. :)
[IES]
Nathan Kegel
Bill,?
The method that Nathan describes is likely known by the IES users on your team, but I focused on the possibility that you would want to feed a schedule into eQuest as was the case in the article that I referenced.?
Would be interested in how your ?issue progresses and what course is chosen of the many.?
Kent
Sent via my mobile
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