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Impact of Nighttime Shut Down on the Prediction Accuracy of Monthly Regression Models for Energy Consumption in Commercial Buildings
Abstract
Regression models of measured
energy use in buildings are widely used as
baseline models to determine retrofit savings
from measured energy consumption. It is less
expensive to determine savings from monthly
utility bills when they are available than to
install hourly metering equipment. However,
little is known about the impact of nighttime
shut off on the accuracy of savings
determined from monthly data. This paper
reports a preliminary investigation of this
question by comparing the heating and
cooling energy use predicted by regression
models based on monthly data against the
predictions of calibrated hourly simulation
models when applied to a medium-sized
university building in Texas with (i) DDCAV
system operating 24 hours per day, (ii)
DDCAV system with nighttime shut down,
(iii) DDVAV system operating 24 hours per
day, and (iv) DDVAV system with nighttime
shut down.
The results of the four cases studied
indicate : 1) when the AHUs are operated 24
hours/day, the annual prediction error of the
cooling regression models is less than 0.5%
of the annual cooling energy consumption;
however, 2) when the AHUs are operated
with nighttime shut down, the annual
prediction error of the cooling models
becomes as high as 6% of annual energy
consumption. It should be noted that the
cases considered here include only single
end-uses of energy and have not investigated
energy-use data which includes multiple end-uses.
Modified regression models are therefore
recommended when AHUs are not operated
24 hours per day and the temperature pattern
is significantly different between pre and post
retrofit years.
Citation
Wang, J.; Claridge, D. E. (1998). Impact of Nighttime Shut Down on the Prediction Accuracy of Monthly Regression Models for Energy Consumption in Commercial Buildings. Energy Systems Laboratory (http://esl.tamu.edu); Texas A&M University (http://www.tamu.edu). Available electronically from https : / /hdl .handle .net /1969 .1 /6746.