ASHRAE Journal - September 2021 - 53

FIRST PLACE | 2021 ASHRAE TECHNOLOGY AWARD CASE STUDIES
FIGURE 1 Central heating and cooling system before (left) and after (left) retrofit.
Before
After
Roof
Hot
Chilled Water
Mechanical Floor
Heat Exchanger
Power
Variable
Speed × 2
9 10
B3
Floor
Ice Storage
Chillers
12
600 + Storage
400 Tons × 2
Absorption
Chillers
3
6
1,665 Tons
× 4
Steam
Boilers
10 Ton/h × 3
Cogeneration Units
With Gas-Turbine
Engines
Power
2,100 kW × 2
Constant
Speed × 4
Heat
2 3 4 8 Centrifugal
Chillers
840 Tons ×
6 Heating
energy retrofi t of the building, the building owner
decided to introduce the commissioning process, which
included a large energy savings target. To fulfi ll this, the
design team made three countermeasures, which comprise
reducing the chilled water capacity, changing to
an all-electric system using maximum effi ciency chillers
and adopting a cogeneration system to reduce peak
power demand through commissioning meetings.ower demand through commissioning meetings.
In this project, the annual trend of chilled water
270 Tons
and
1,161 kW
decided to introduce the commissioning process, which
included a large energy savings target. To fulfi ll this, the
design team made three countermeasures, which comprise
reducing the chilled water capacity, changing to
an all-electric system using maximum effi ciency chillers
and adopting a cogeneration system to reduce peak
In this project, the annual trend of chilled water
demand was carefully researched during the investigation
phase of commissioning prior to design phases.
It was determined that chilled water system capacity,
including one backup chiller, could be reduced by 20%,
using actual energy consumption data for the past three
years and energy-savings calculations that reduced outdoor
air volume, while satisfying suffi cient air volume
per person. The other advantages of this approach are
creating replacement space and decreasing initial cost.
Based on the reduced chilled water capacity, a variety
of central heating and cooling systems were studied by
the design team to uncover optimum and signifi cant
energy reductions. These systems included a gas-fi red
steam system, which is the same as the original system;
an all-electric heat pump system; mixed systems using
both and more. Thirteen variations of central heating
and cooling systems were compared for initial cost,
energy cost and annual cost based on their initial cost,
primary energy consumption and electrical peak load.
An all-electric heat pump system using variable-speed
centrifugal chillers and air-source heat pumps was the
demand was carefully researched during the investigation
phase of commissioning prior to design phases.
It was determined that chilled water system capacity,
including one backup chiller, could be reduced by 20%,
using actual energy consumption data for the past three
years and energy-savings calculations that reduced outdoor
air volume, while satisfying suffi cient air volume
per person. The other advantages of this approach are
creating replacement space and decreasing initial cost.
Based on the reduced chilled water capacity, a variety
of central heating and cooling systems were studied by
the design team to uncover optimum and signifi cant
energy reductions. These systems included a gas-fi red
steam system, which is the same as the original system;
an all-electric heat pump system; mixed systems using
both and more. Thirteen variations of central heating
and cooling systems were compared for initial cost,
energy cost and annual cost based on their initial cost,
primary energy consumption and electrical peak load.
An all-electric heat pump system using variable-speed
centrifugal chillers and air-source heat pumps was the
most effi cient. But this system was expensive due to
changing the steam system to a hot water system. So it
was decided to postpone replacing part of the steam system
and to replace this in the near future. A gas-enginedriven
cogeneration system was added for the reduction
of peak power demand and energy cost. Peak power
demand is now almost the same as the original peak
demand. This modifi ed system was selected.
The renovated central plant has centrifugal chillmost
effi cient. But this system was expensive due to
changing the steam system to a hot water system. So it
was decided to postpone replacing part of the steam system
and to replace this in the near future. A gas-enginedriven
cogeneration system was added for the reduction
of peak power demand and energy cost. Peak power
demand is now almost the same as the original peak
demand. This modifi ed system was selected.
The renovated central plant has centrifugal chillers,
air-source heat pumps and cogeneration units.
The centrifugal chillers are the main chillers in lieu of
absorption chillers. A large amount of the steam system
was changed to hot water as a heating medium to
reduce heat loss. Air-source screw heat pumps, which
are more effi cient than boilers, were introduced as the
primary heaters. The cogeneration units are driven by
gas engines, which are more effective and have a lower
maintenance cost than gas turbine engines. The exhaust
heat from the cogeneration units is reused as steam
for an absorption chiller and hot water as a source for
domestic hot water generation (Figure 1).
The variable chilled and hot water supply system was
designed using the estimated terminal head. These
pump heads were carefully recalculated based on asbuilt
drawings and were selected based on their best
effi ciency point in the construction phase. Several airhandling
units, whose coils were changed from steam to
hot water, were changed to a variable-air-volume system
from a constant-volume system. They were added to a
demand-controlled ventilation system using indoor CO2
The variable chilled and hot water supply system was
designed using the estimated terminal head. These
pump heads were carefully recalculated based on asbuilt
drawings and were selected based on their best
effi ciency point in the construction phase. Several airhandling
units, whose coils were changed from steam to
hot water, were changed to a variable-air-volume system
from a constant-volume system. They were added to a
demand-controlled ventilation system using indoor CO2
S E P T E M B E R 2 0 2 1
ashrae.o rg
a s h r a e . o r g
ASHRAE JOURNAL
A S H
A E J O U R N A L
5 3
Recovery Chiller
1
Well Water
Heat
Pump 5
150 Tons or
596 kW
Absorption
Chiller
7
300 Tons
Cogeneration Units
With Gas Engines
Power
1,000 kW × 2
Hot Water
Boilers
1,163 kW
× 4
Steam
Boilers
2 ton /h × 4
Steam Water
Chiller Plant Size
8,660 Tons
Domestic
Hot Water
Tank
Air Source Heat
Pump
6
Chilled Water
1,195 Tons of
Heating 3,080 kW
Hot Water
Solar Hot Water
65 kW
Domestic
Hot Water
Steam for
Tank
Power
Temporary Use
Chiller Plant Size
6,955 Tons
ers, air-source heat pumps and cogeneration units.
The centrifugal chillers are the main chillers in lieu of
absorption chillers. A large amount of the steam system
was changed to hot water as a heating medium to
reduce heat loss. Air-source screw heat pumps, which
are more effi cient than boilers, were introduced as the
primary heaters. The cogeneration units are driven by
gas engines, which are more effective and have a lower
maintenance cost than gas turbine engines. The exhaust
heat from the cogeneration units is reused as steam
for an absorption chiller and hot water as a source for
domestic hot water generation ( igure 1)
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ASHRAE Journal - September 2021

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