Using measured equipment load profiles to 'right-size' HVACsystems and reduce energy use in laboratory buildings (Pt. 2) Page: 4 of 14
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Labs21 Benchmarking Database - Building Peak Electrical Demand
5 6 7 8 9 10 30 11 12 13 14 16 29 31 32 36 38 39 36 43 48 56 57 59 60 63 66 69 72 73 74
Figure 1. Total electrical demand (W/gsj) for various laboratory facilities recorded in the Labs21 energy
2.2 Case Study: Measured vs. Estimated Loads
The University of California (UC) Davis campus initiated a project to measure equipment loads at
two of its laboratory buildings in order to use the measured data as a basis for sizing the HVAC
systems in the design of new comparable facilities. In each building, measurements were made
for several laboratory spaces, representing a range of different uses within that building. Clamp-
on meters were used to take continuous measurements of equipment electrical loads for each lab
space. Each measurement period was typically about 2 weeks long. The measurements were
taken when the labs were nominally fully occupied and used. Three quantities were measured:
" Apparent instantaneous power: The product of the voltage and the current at any given
" Actual instantaneous power: This is the actual instantaneous power draw - which becomes
a thermal load to the space.
" Average interval power: This is obtained by averaging the actual instantaneous power over
each 15-minute interval (this quantity is typically measured by utility interval meters to
determine demand charges).
Figure 2 shows the 15-minute interval measured data for two laboratory spaces, each of which
was measured for about 4 weeks. The figure shows the peak apparent instantaneous power, peak
actual instantaneous power and the average interval power for each 15-minute interval. As
expected, in each interval the peak apparent power is always equal to or higher than the peak
actual power, which in turn is always higher than the average interval power. In space A, the
overall peak apparent power is about 8 W/sf and the overall peak actual power is about 7.5
W/sf. The maximum interval power is only about 3.75 W/sf, which is less than half the overall
peak apparent power. In space B, the overall peak apparent power is about 40 W/sf, the overall
peak actual power is about 29 W/sf, while the maximum interval power is about 6 W/sf - which
is only 15% of the overall peak apparent power.
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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/m1/4/: accessed April 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.