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

Bishop, Bill wbishop at pathfinder-ea.com
Thu Oct 6 06:45:13 PDT 2011



Heat gains from lighting in spaces is shared between the space and its
plenum depending on the values for LIGHT-TO-SPACE and LIGHT-TO-RETURN.
For other electrical equipment and for occupants, the heat gains all go
to the space, but are divided into latent and sensible  components. I
believe all of the electricity consumed by lighting and equipment is
converted to heat gains. The heat gains are converted to cooling loads
using weighting factors. The weighting factors can be modified by
specifying the convective/radiative splits, through keywords light
LIGHT-RAD-FRAC. The radiative portion can be absorbed by walls and
furniture and so does not create an immediate (for that hour) cooling


You can create custom hourly reports to see how this plays out in the
building by using the "Building Loads" variable and selecting "Building
light heat load", "Building light cool load" and "Building light elec
total". Similar variables can be selected for individual spaces.


If you haven't already downloaded it, I recommend looking at the DOE-2
Engineers Manual: 


Section 2.5 - Interior Loads describes the algorithms for loads


Keep in mind that changing your lighting and equipment values will
impact cooling energy as well. You may be seeing small changes in
heating energy but much larger changes in cooling energy, depending on
other factors like your envelope, ventilation loads etc.







From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Taylor
Sent: Wednesday, October 05, 2011 11:18 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Lighting densities and Electrical
equipmentcontributing 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

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

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