ASHRAE Journal - December 2023 - 55

HONORABLE MENTION 2023 ASHRAE TECHNOLOGY AWARDS
Energy Efficiency
An energy performance model was completed, and
the resulting energy use intensity (EUI) showed that
with a proposed photovoltaic panel installation, the
project will realize a potential 29% energy cost savings
compared to the ASHRAE/IES Standard 90.1-2010
Appendix G baseline. These designed savings include:
 In addition to its high performance building
envelope, unique architectural elements act as external
south- and west-facing shading devices for the south
lobby and meeting room block, respectively.
 The chilled water plant supplies water at 38ºF
(3.3°C) with a return at 56ºF (13°C) through 2,720 ft
(829 m) of piping main distribution via variable primary
and variable secondary distribution. The large system
delta T reduces the system flow and reduces pipe size
or installation cost. At reduced flow, the pump motor
energy savings greatly outweighs the chiller operating
cost penalty.
 Eighteen AHUs supply air at a low discharge
temperature of 45ºF (7.2°C) and 50ºF (10°C), providing
a reduced airflow over standard temperature airflows
by 537,500 cfm (253 672 L/s). This reduction in airflow
provides for reduced air system size or installed cost and
the associated fan operation energy savings.
 In addition to the airside economizer, a waterside
economizer is included as part of the design via a plate
and frame heat exchanger to provide for the 24/7/365
secondary cooling demands.
 Addressable, networked, centralized lighting
controls, vacancy/occupancy sensors and dimming
systems, including daylight dimming systems, were
included to achieve optimum energy savings.
Based on annual energy consumption data
provided by the Las Vegas Convention and Visitors
Authority (LVCCA) for a period from July 2021 to June
2022, the annual site energy use intensity (EUI) is
51.1 kBtu/ft2·yr (580 MJ/m2·yr). This analyzed period
was the convention center's first fully occupied year of
operation. The published Convention Center site EUI
from Energy Star's U.S. National Medium Referenced
Values for All Portfolio Manager Property types is
56.1 kBtu/ft2·yr (637 MJ/m2·yr). The EUI for the new Las
Vegas Convention Center is operating and performing
9% better than the national average performance.
The monthly power demands from the building are
CASE STUDY
in line with the chillers' annual trend and provide
confirmation that the variable primary and variable
secondary system(s) save energy in large complex
distribution systems, reducing the overall compressor/
mechanical refrigeration system operation. The
variable-primary and variable-secondary system not
only simplifies the operations for the facility's operation
team but also fluctuates the flow range in the primary
loop to avoid low-return water syndrome. Independent
secondary pumping systems can fully use the thermal
mass built in with the piping network before initiating
the chiller's primary loop, which reflects savings from
the chillers and primary pump's reduced operation.
Variable flow within the condenser water loop avoids
overflow with a low return temperature back into the
chillers as well as controls of the chillers' minimum
head pressure.
The same piping arrangement and design using
variable primary and variable secondary loops is
configured on the heating hot water side, reducing the
operation of the condensing boiler from the natural gas
utility " therm " consumption.
Innovation
The building in the Mohave Desert with high internal
loads required a cooling dominant system. The chilled
water coils will not require freeze protection in winter.
This establishes the practical lowest chilled water
temperature of 38ºF (3.3°C) without using glycol. The
design chilled water return temperature is 56ºF (13°C).
The low-temperature discharge air and chilled water
distribution design provide a collaborative, creative
design approach in exhibition halls and main lobby.
Although the chiller's peak kW/ton is increased for
38ºF (3.3°C) chilled water supply, for a commercial
building, the temperature is variable during partial
load conditions; with a 18ºF (10°C) delta T and reduced
system flow, the trade-off of the chiller peak load
efficiency penalty yields a higher return from the
chilled water pump horsepower reduction in both
primary and secondary chilled water pumps. Due to the
building capacity and the vast distribution, the variable
primary and variable secondary system inherits benefits
from both the primary/secondary and the variable
primary system.
This design strategy simplifies the complexity of the
Mehdi Jalayerian, P.E., is senior managing director, Suzan Sun-Yuan, P.E., is mechanical technical authority and Kenneth Lechner is a studio leader at Stantec Consulting Services.
D ECEMBER 2 0 2 3
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