ASHRAE Journal - July 2014 - 61

2014 ASHRAE TEcHnology AwAR d cASE STudi ES
nology AwAR
ARd
STudiES

Above Shopping mall at the access to ICC.
Left Elevator lobby overview of office zones.

The ICC has a gross floor area of approximately
3,455,215 ft2 (321,000 m2), not counting the hotel that
occupies the skyscraper's top 17 floors. The building
serves as a commerce center with commercial offices
(primarily international financial firms), shopping
malls, and the hotel.
Cooling is provided by a central chilling system on
the eighth floor that consists of six identical centrifugal
chillers (each with cooling capacity of 7230 kW [2,056
ton]) and 11 indoor cooling towers (each designed
with motor power of 150 kW). Plate heat exchangers
deliver cooling from lower floors to higher ones to avoid
extremely high static pressure.

Improved System Configuration
Energy and operation performance of the HVAC
system was modeled with different configuration/
equipment options using local weather conditions and
simulated operating conditions. Energy benefits from
alternative designs were assessed and optimized designs
were created and implemented.

Simplification of Secondary Water Loop Systems
The original primary-secondary pumping paradigm for the third and fourth zones in the building's
upper stories used primary constant speed pumps
at the secondary side of each heat exchanger. The
major function of these primary pumps is to provide
the circulation force of chilled water to overcome the
pressure drop of heat exchangers. However, under
part load, especially under light load, these primary
chilled water pumps would contribute a large portion of the total energy used in the third and fourth
zones.
To reduce initial cost and save operating energy, the
primary pumps were eliminated. The simplification of

the secondary water loop required no extra investment
and the site assessment shows that the annual energy
savings using the optimized design is more than 1.0 million kWh.

Cooling Tower System Selection and Operation
The cooling tower system's original design used twospeed (two-stage) fans (later replaced by variable speed
fans with the minimum allowed speed of 37 Hz). To
maximize energy savings, the fans were changed to variable speed fans using variable frequency drives (VFD).
And, the minimum operating frequency of the fans was
reduced from 37 Hz to 20 Hz. Based on the commissioning test results, such use of VFDs and lower operating
frequency can provide an annual energy savings up to
2.36 million kWh.

Daylighting Design
In the ICC, daylighting is incorporated by using curtain walls in offices and the lobby. The design allows
maximum daylight access, lowering the demand on artificial lighting.

Optimized Control Strategies
IAQ and Thermal Comfort
On each typical office floor in the building, an individual air-handling unit usually provided cooled air to
variable air volume (VAV) boxes located in a number
of zones. Conventional fresh air control modulated the
total supply fresh airflow rate to ensure the measured
CO2 concentration of the main return air is maintained
at the preset set-point.
But, using conventional control may cause oversupplied total fresh air during low occupancy.
Therefore, a robust demand controlled ventilation
(DCV) control for multizone office floors based on
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