5.1.1 Central chiller plant
The chiller is one of the most energy intensive items of equipment in a building.
An efficient central chiller plant can significantly contribute to the overall energy
saving of the building.
Commercial chillers can either be air cooled or water cooled. For air cooled
chillers, short-circuiting hot discharged air will lead to inefficient operation of the
chillers, which will substantially affect the energy performance of air conditioning
system. To avoid short-circuiting, air cooled chillers should be located on an
open roof whenever possible.
In Hong Kong, most of the retail outlets are located in the podium of a
comprehensive development. Due to planning constraints, air cooled chillers
may not be located on an open roof. Therefore, indoor air cooled chillers may
be inevitable. In such case, air intake and exhaust louvers should be properly
arranged to avoid air short-circuiting. The recommended strategies are as
follows:
Figure 104 Air cooled chiller
1
Provide louvers with different
building orientations
2
Adequate separation between
intake and exhaust
3
Provide intake louvers facing south-
east to minimise short-circuiting due
to the
direction in
summer
Water cooled air conditioning system (WACS) consumes 35% less energy compared with an air cooled chiller system.
Although the installation cost of water cooled system is slightly higher than an air cooled system, the payback period
is expected to be about 2 to 3 years. WACS should be considered for shopping malls to improve the overall energy
performance of the air conditioning system.
Location of the chiller plant should also be considered to minimise the airborne and structural borne noise nuisance to
occupants and the neighbourhood.
5.1.2 Chilled water circulating system
Chilled water is circulated to air-conditioning equipment by water pumps. Variable speed pumps should be used which
are capable of varying the flow of chilled water in response to the change in building cooling load. Energy used by both
the pump and the chiller can be saved.
For retail tenants, the on/off control valve for the
should be the “Normally Closed” type to enable the
saving of pump power when the FCU is switched off. As the tenants’ operating hours may be different according to the
nature of their business, it is preferable to install individual motorised on/off valves for each shop to enable the A/C supply
to be shut down independently. The valve should be operated by the building management system (BMS) to suit the
different business hours of tenants.
Energy meters should be provided in addition to motorised control valves for the anchor shops to facilitate energy
management. To provide incentives for tenants to save on energy, it is also recommended to charge the A/C cost by
actual demand rather than based on the rentable area.
Piping accessories, such as isolation valves, strainers, etc., should be minimised to reduce the energy loss.
5
Energy efficient building systems for shopping malls and shop spaces
5.1
Heating, ventilation and air-conditioning (HVAC)
Hong Kong Green Building Council 127
