[Equest-users] Lighting densities and Electrical equipment contributing to Space Heating

John Bixler JBixler at Sebesta.com
Thu Oct 6 06:24:37 PDT 2011


A number of things play into the question you are asking.

*         Different types of lighting have different efficiencies.  Incandescent lights create a lot of heat, LEDs create practically no heat.  Fluorescent is somewhere in between but create much less heat then incandescent

*         The style of light installed - is it pendant hung in the space?  If so, 100% of the created heat is given to the space.  Is it recessed?  If so, a portion of the heat is given to the plenum, and some of the heat given to the plenum leaves the building as relief air (in fact, it's possible that all the plenum heat leaves the building in the case of a 100% outdoor air system)

*         The schedule of the lights.  Were you looking at yearly consumption or peak heating load?  Peak heating load is typically calculated with the lights (and occupancy and misc loads) at 0%.  If you were looking at yearly consumption, but your modeled facility has the lights turned off for a majority of the time, the impact may be minimized.

Point being, you have to consider more than just lighting density when you make this analysis.

John Bixler, EIT, LEED AP BD+C
Mechanical Designer
Sebesta Blomberg
sebesta.com | P  319.364.1005 | M  319.558.9299

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From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Taylor Sharpe
Sent: Wednesday, October 05, 2011 10:18 PM
To: John Bixler
Subject: [Equest-users] Lighting densities and Electrical equipment contributing to Space Heating

Hi everyone,

I feel that this topic must have been discussed at some point, but an exhaustive archive search got me nowhere, so I thought I'd throw together a post of my own, especially since I'm working on an eQuest model of a small server building which is heated in part by a large number of computers that run many hours every day.

I'm interested in how eQuest treats electric loads - from lights, computers, refrigerators, etc - as regards space heating.  I had always assumed that, especially in the case of lights, much of the energy used would be converted to heat within the building, and contribute to space heating.

However, I set up an experiment to test this and found that the results were far different from what I'd expected: I upped the lighting density in an existing natural-gas-heated building model by about 15x and compared the electric use from before and after the lights were increased.  I converted all values to mmBtus for easy comparison.  To my surprise, I found that only a very small fraction (about 6%) of the mmBtus added to the building through those lights contributed to space heat.  The kWh recorded were increased hugely, but the heating energy required to keep the building heated was almost the same in both cases.

I repeated the experiment, upping misc. equipment instead of lighting, and saw a similar result.

Does anyone have any knowledge of what equations eQuest uses to decide how much electrical energy use is converted to heat and added to the space in which it is installed?

Taylor Sharpe
Sharpe Energy Solutions
newspectrum at gmail.com<mailto:newspectrum at gmail.com>
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