Using measured equipment load profiles to 'right-size' HVACsystems and reduce energy use in laboratory buildings (Pt. 2) Page: 8 of 14
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and 10 W/sf and one space is high-intensity at about 17 W/sf. This is a fairly common situation,
where one or two labs have very high equipment loads compared to the others. The problem
arises when all these labs are served by a single air-handling unit with zone reheat coils for
temperature control (a widely used HVAC strategy). The high-intensity labs then drive the
supply air temperatures and flows to handle their high equipment loads, and as a result, all the
other labs have to use reheat to maintain desired temperatures. This issue does not always come
up during design, because some designers assume a uniform equipment load intensity for all
laboratory spaces served by an air handler and assume no variation between those spaces.
Energy simulations conducted during the design phase that reflect this assumption will not show
the increased reheat energy use due to load variation.
Range of measured W/sf (15min interval power)
3L2A 3L2B 3L2C 3L2D 3L2E 3L2H 3L2L 3L2M 2L2G 2L2H 3L1N
Figure 5. Range of measured 15-min interval power for various laboratory spaces in a building at UC
Davis. The upper and lower ends of the lines represent maximum and minimum respectively. The upper
and lower ends of the boxes represent 99th and 1St percentiles of the measurements respectively.
3.2 Energy Use Analysis
In order to analyze the increase in reheat energy use arising from equipment load variation,
several parametric energy simulations were conducted using the DOE-2.2 energy simulation tool.
The simulation model consisted of a set of five laboratory spaces served by a single air-handling
unit (figure 6). In order to eliminate envelope-related load variations across these spaces, the
boundary conditions of all the spaces were assumed to be adiabatic. The lighting and occupancy
load profiles in all the spaces were identical.
Each parametric case consisted of two simulations:
" Simulation with load variation ("Var"): One zone has a "high-intensity" equipment load
profile, while the remaining zones have a "typical" load profile.
" Simulation with uniform loads ("Uni"): All zones have the same uniform equipment load
profile, which represents an area-weighted average of the "high-intensity" and "typical"
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Mathew, Paul; Greenberg, Steve; Frenze, David; Morehead, Michael; Sartor, Dale & Starr, William. Using measured equipment load profiles to 'right-size' HVACsystems and reduce energy use in laboratory buildings (Pt. 2), article, June 29, 2005; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc901308/m1/8/: accessed May 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.