Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question

Modeling artificial light

asked 2015-09-17 10:27:49 -0600

Maryam's avatar

updated 2015-09-17 10:49:58 -0600

How can I change the properties of a luminaire such as lumen output and type(LED, fluorescent, etc.) in Openstudio?

edit retag flag offensive close merge delete

3 Answers

Sort by ยป oldest newest most voted

answered 2015-09-18 11:58:53 -0600

updated 2015-09-18 12:19:00 -0600

@Maryam, the answer to your question is no, OpenStudio cannot currently use Radiance to (spatially) simulate electric lighting. Sorry! It is a bit confusing since there is that luminaire object there, but as David intimated these luminaires are not exported to Radiance. They also do not currently support photometry -- only position and load.

To be clear, the Radiance routines in OpenStudio do modify the electric lighting load schedules, but they work simplistically off of the "Daylighting Control Point" illuminance, linearly interpolating the lighting power fraction based on the (Radiance-calculated) daylight illuminance versus the control point's setpoint. What OpenStudio-Radiance does not do is perform a spatial simulation of the electric lighting using photometric data (e.g. "IES Files").

edit flag offensive delete link more

answered 2015-09-17 11:01:31 -0600

This is a common misconception. The way EnergyPlus works is that you input a Lights object (documentation), and specify which zone it serves, its lighting power and fractional schedule, and how the heat is distributed.

EnergyPlus doesn't care whether your Lightsobjects are enough to provide enough lighting to your zone.

If you put a daylighting control in the zone, EnergyPlus just assume that whatever lighting power your specified will provide the illumance setpoint you have specified when your fractional schedule is 1 and its nighttime.

In your case, whether you have a LED or a fluorescent fixture, you'll just have less Watts for the lights object, and you could tweak the fraction radiant and fraction visible.

edit flag offensive delete link more


So does this mean that Radiance through Openstudio could not be used for simulation of electric light?

Maryam's avatar Maryam  ( 2015-09-17 11:23:05 -0600 )edit

answered 2015-09-17 11:11:35 -0600

updated 2015-09-17 12:24:35 -0600

We did make a Luminaire object when we first created OpenStudio that works just like a Lights object, except it does have a position in space and an orientation/rotation. Another difference is that it can only be (W) vs. (W/person) or (W/area). The intent was at some point in the future this could be used for Radiance simulation of electric lighting (vs. daylighting) but that isn't on our short term plan.

edit flag offensive delete link more


@Maryam, my comment was moved to an answer. To follow up on your comment. Currently we don't store the lighting distribution characteristics with a luminaire. I also don't know if luminaire is exported as part of the Radiance workflow @rpg777 can answer this, but with 1.9.0 moving to a measure based Radiance integration, someone could write a measure to export the luminaire objects, but the performance characteristics needed to simulate electric lighting would have to come from somewhere else; for example a CSV file that maps OpenStudio objects to performance data.

David Goldwasser's avatar David Goldwasser  ( 2015-09-17 14:35:19 -0600 )edit

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer


Question Tools


Asked: 2015-09-17 10:27:49 -0600

Seen: 675 times

Last updated: Sep 18 '15