ASHRAE Journal - August 2022 - 25
TECHNICAL FEATURE
discharge volumes equal to their minimum ventilation
requirements and then raises them as necessary to satisfy
positive sensible loads and to lower the discharge
air temperature enough to minimize stratifi cation. It
then continues to raise the discharge air volume in the
critical zone(s) until the volume of outdoor air meets the
requirement from the multizone ventilation equations
discussed earlier. Then the cost is calculated for this
iteration, and the algorithm moves on to the next one.
The algorithm stops once the cost begins to rise between
iterations or an infeasible condition is encountered,
and the set of variables with the lowest cost is sent to the
real system to be applied. When conditions have varied
suffi ciently, such as fi fteen minutes later or if a zone's
sensed occupancy changes, the process repeats, and new
setpoints are calculated and applied.
This discrete approach sidesteps the diffi culties (and
differential equations) of a more dynamic model,
while being a more complete solution than a trim-andrespond
approach like that of RP-1747. However, since
it is too complex to be used natively in standard control
logic, then until it is added directly into building automation
software, it may instead be written in a language
like Java or Python and interface with the system as a
software plug-in or via standardized communication
protocols like BACnet. Once created, it scales easily
across both new and existing systems, without the need
for additional hardware.
Performance
As part of the development of the above algorithm, it
was coded in Java and uploaded as a software add-on to
the building automation system of a 50,000 ft2 (4,645 m2)
offi ce and classroom building in ASHRAE Climate Zone
5A, where it was compared against the building's baseline
control sequence. For the early summer period seen
in Figure 3, it showed a 70% reduction of hot water consumption,
42% of chilled water, and 53% of electricity,
leading to an overall operating cost savings of 54%.
This is perhaps an exceptional result, but during the
cooling season, such a scheme can be expected to generate
savings on the order of 25% to 30%. Even while
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ASHRAE Journal - August 2022
Table of Contents for the Digital Edition of ASHRAE Journal - August 2022
Contents
ASHRAE Journal - August 2022 - Intro
ASHRAE Journal - August 2022 - Cover1
ASHRAE Journal - August 2022 - Cover2
ASHRAE Journal - August 2022 - 1
ASHRAE Journal - August 2022 - Contents
ASHRAE Journal - August 2022 - 3
ASHRAE Journal - August 2022 - 4
ASHRAE Journal - August 2022 - 5
ASHRAE Journal - August 2022 - 6
ASHRAE Journal - August 2022 - 7
ASHRAE Journal - August 2022 - 8
ASHRAE Journal - August 2022 - 9
ASHRAE Journal - August 2022 - 10
ASHRAE Journal - August 2022 - 11
ASHRAE Journal - August 2022 - 12
ASHRAE Journal - August 2022 - 13
ASHRAE Journal - August 2022 - 14
ASHRAE Journal - August 2022 - 15
ASHRAE Journal - August 2022 - 16
ASHRAE Journal - August 2022 - 17
ASHRAE Journal - August 2022 - 18
ASHRAE Journal - August 2022 - 19
ASHRAE Journal - August 2022 - 20
ASHRAE Journal - August 2022 - 21
ASHRAE Journal - August 2022 - 22
ASHRAE Journal - August 2022 - 23
ASHRAE Journal - August 2022 - 24
ASHRAE Journal - August 2022 - 25
ASHRAE Journal - August 2022 - 26
ASHRAE Journal - August 2022 - 27
ASHRAE Journal - August 2022 - 28
ASHRAE Journal - August 2022 - 29
ASHRAE Journal - August 2022 - 30
ASHRAE Journal - August 2022 - 31
ASHRAE Journal - August 2022 - 32
ASHRAE Journal - August 2022 - 33
ASHRAE Journal - August 2022 - 34
ASHRAE Journal - August 2022 - 35
ASHRAE Journal - August 2022 - 36
ASHRAE Journal - August 2022 - 37
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ASHRAE Journal - August 2022 - 49
ASHRAE Journal - August 2022 - 50
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ASHRAE Journal - August 2022 - Cover3
ASHRAE Journal - August 2022 - Cover4
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