ASHRAE Journal - August 2024 - 40

TECHNICAL FEATURE
FIGURE 1 Server rack hot aisle/cold aisle containment.
Step 1: Reduce Load by Upgrading, Virtualizing and Consolidating IT
Equipment (39% of Total Energy Savings)
By upgrading, virtualizing and consolidating the
existing IT inventory into a high-density computing
environment, the team reduced the IT loads, reduced
the required electrical and cooling capacities and
also enabled a reduction in the footprint of the data
center. The new IT equipment was also rated for higher
operating temperatures than the obsolete equipment
that was replaced.
the data center.
* Economization potential. The data center's location
on a perimeter wall and the local climate indicated the
potential for airside economization.
* Chilled water plant operation. Total
consumption of the chilled water plant was assessed
comprehensively, considering chiller, pump and
cooling tower power consumption.
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ASHRAE JOURNAL ashrae.org A U G U ST 2 0 2 4
Step 2: Serve Loads More Efficiently by Upgrading HVAC Systems,
Implementing Economization and Decoupling the Data Center from the
Central Plant (54% of Total Energy Savings)
In tandem with the IT upgrades, the project team
undertook a series of HVAC improvements that
leveraged modern data center cooling strategies,
such as expanded operating temperatures
and containment strategies. Critically, these
compounding upgrades facilitated the complete
decoupling of the data center from the central cooling
plant, enabling setback of the building's chillers,
cooling towers and pumps during unoccupied hours.
This was a major operational improvement, since
prior to the energy savings performance contract
(ESPC), the data center's cooling design required the
central chiller plant to run 24/7, including during
nighttime and weekend unoccupied periods. To
achieve this, the team:
* Implemented hot-aisle/cold-aisle containment for
server racks with physical plexiglass barriers between
the aisles to reduce mixing of cold supply air and hot
return air (Figure 1). The containment system allowed
for better control of the air temperature entering
the racks, which increased the temperature at which
economization could be enabled from 65°F to 81°F
(18°C to 27°C). This comprised 16% of HVAC savings for
this step.
* Adjusted cooling setpoint temperature from 66°F
to 78°F (19°C to 26°C) and increased the allowable
humidity range based on revised ASHRAE guidance for
data centers to enable a wider range of space conditions
and more airside economization. It comprised 9% of
HVAC savings for this step.
* Installed exhaust and economization louvers and
fans to allow airside economization whenever outside
enthalpy was lower than the return air enthalpy
JOSHUA BOOKSTAVER
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ASHRAE Journal - August 2024

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