60 Miller Street North Sydney - Achieving high performance HVAC control via 'democratic control'

Purpose

60 Miller Street, North Sydney was built during the 1980s. The property consists of 12 office levels, a basement car park, retail units at ground level and a roof top plant room with a net lettable area (NLA) of 18,219m2.

The performance of the existing building, resulting from previously completed extensions, was having a significant impact on the overall base building NABERS Energy Rating which was rated at 2.5 star without GreenPower in 2011." data-share-imageurl="">

Wednesday, September 2, 2015

Purpose

60 Miller Street, North Sydney was built during the 1980s. The property consists of 12 office levels, a basement car park, retail units at ground level and a roof top plant room with a net lettable area (NLA) of 18,219m2.

The performance of the existing building, resulting from previously completed extensions, was having a significant impact on the overall base building NABERS Energy Rating which was rated at 2.5 star without GreenPower in 2011.

DEXUS embarked on a plant and controls upgrade to increase the building's NABERS Energy star rating, targeting 5 stars.

Approach

A staged approach was taken to investigate the cause of the building’s poor performance and implement upgrades and retrofits to the mechanical plant. An initial investigation of current performance determined where energy was being used throughout the building and its effectiveness.  This identified several issues, including supply fans running at 100%, incorrect placement of zone temperature sensors, and inefficient cooling plant.

A VAV optimisation control strategy was introduced in response to these issues and the building was tuned to overcome the highly sensitive nature of the existing controls.  Season-based zone temperature control bands were also introduced to allow internal temperatures to drift with ambient conditions and avoid setting a single year-round temperature set point.

The DX cooling plant was replaced with two 800kWr high efficiency chillers and a new Chilled Water Control Strategy was designed in order to optimise the chillers by considering all of the associated plant (such as the pumps and cooling tower fans). The new BMS graphics include a chiller sequencing page with the operating Coefficient of Performance (COP) for each chiller, system operating status and trend logs.

Results

60 Miller Street has realised significant benefits from an energy efficiency upgrade, with extensive controls modifications being the clear differentiator.

Buildings are dynamic with constant changes in ambient conditions and occupancy levels. The logic behind the VAV controls (using zone voting) tracks the behaviour of the building to provide just enough energy to meet the zone demands, and always trying to reduce energy when the votes are satisfied. The fan efficiency is now being maximised and the tuning process streamlined.

Considering the existing infrastructure of the building, the outcome has been very successful. The 60 Miller Street project proves that a well engineered BMS can provide substantial energy savings and overcome many design challenges.

The project has yielded a 50% reduction in energy use at 60 Miller Street, with a 57% improvement in energy intensity between FY11 and FY14.

“Buildings are dynamic; responding to constant changes in ambient conditions and occupancy levels. The logic behind the zone-voting tracks implemented at 60 Miller Street North Sydney controls the behaviour of the building’s HVAC system to provide just enough energy to meet the zone demands, and always seeking to reduce energy when the votes are satisfied. The fan efficiency is now being maximised, the tuning process is streamlined and coupled with a conversion from DX units to central chiller plant, the building’s energy consumption has been halved since the project was implemented.”