Jun 3, 2017 - and energy efficiency into an iconic building located in Melbourne's financial ... Managed by facility man
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June 2017 / ISSUE 102 / FREE
Feature
CHILLER QUEEN
To assist in this planning, a new control system was installed (see breakout box, “An AIRAH Award winner installed”.) According to Chirayu Shah, M.AIRAH, general manager for Conserve It, one of the benefits of its installation at 100 Queen Street was the ability to collect data better than the building management system (BMS). “It collects over 11 points per chiller, and then calculates over 50 points using those 11 sensor inputs,” he says. “All of these points, along with sensors and calculated data points for pumps, cooling tower and common temperatures, flows and pressures in a central plant are collected every 15 minutes. Some critical points are logged every few minutes, or on a change of value.” This data is stored locally, and used to build reports and charts within the interface, or exported for further analysis.
Due to the plantroom’s level-six location, the new chillers were required to be delivered in kit form and assembled in situ once craned into the plantroom. Similarly, the old chillers had to be dismantled for removal the same way.
UTILISING DATA A main chille r-plant upgra de combine of an AIRAH d with the a Award-winn ddition in g controls sy and energy stem has bre efficiency in athed new li to an iconic fe building loca financial distr ted in Melbo ict. Sean Mc urne’s Gowan repo rts. Melbourne’s 100 Queen Street is typical of many of the city’s buildings currently undergoing refurbishment. Built in 1993 to complement the restoration of the heritage-listed former Melbourne Stock Exchange and ES&A buildings, the 37-storey commercial office tower’s original mechanical-services plant were due for upgrade being near to the end of their useful life. Managed by facility manager Jones Lang LaSalle (JLL), 100 Queen Street is one of a number of buildings in Melbourne’s financial district to be owned and occupied by ANZ. Others include the neighbouring 90 Queen Street building, and those around the corner in Collins Street.
Since late 2012 when it won the service and maintenance contract for 100 Queen Street, Airmaster Australia has worked closely with JLL to improve the energy performance and NABERS Energy rating of the building. This work included efficiency upgrades to the building’s original main chilled-water plant, consisting of two aging high-load chillers, two low-load chillers, cooling towers, pumps and associated ancillary equipment. Nearing the end of its useful life, plans were put in place to begin design work on its replacement and upgrade.
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Following the system’s installation at 100 Queen Street, over six months of data was collected and used by mechanical services engineer, Arup, to help plan the upgrade of the building’s original main chilled-water plant. Arup senior engineer Andrew Tsakmakis says one thing the new control system does incredibly well is collect data. “Without data we are moving in the dark,” says Tsakmakis says. “The load data collected was used to help make the decision about whether or not the constructions staging of the chillers was going to work. In the end, this was very successful, and we had confidence in the data produced.” Based on Arup’s design brief, with some changes made to the piping layout, the two original high-load chillers were replaced by Airmaster in late 2015 in an installation that required careful planning and coordination. According to Airmaster’s projects manager Phil Barrow, a number of challenges presented themselves – not least the restricted access to the existing plantroom. Due to the plantroom’s level-six location, the new chillers were required to be delivered in kit form and assembled in situ once craned into the plantroom.
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A number of challenges presented themselves at 100 Queen – not least the restricted access to the existing plantroom.
Similarly, the old chillers had to be dismantled for removal the same way. Access was created by cutting into the concrete slab of the level-seven balcony to access the plantroom below. A support frame was built underneath the proposed penetration, and a catch-tray installed for all the slurry.
“The penetration was done by cutting the slab area into several small sections approximately 400mm² using a concrete saw, and then lifted out via anchor points installed with an A-frame support with block and tackle,” says Barrow. The penetration was also made weatherproof for the duration of the works.
AN AIRAH AWARD WINNER INSTALLED A PlantPRO control system was installed at 100 Queen St. Winner of the Product of the Year award at the 2015 AIRAH Awards, it is designed to provide control of the chiller plant in a way that delivers efficiencies beyond that of the plant’s individual components. Engineered and developed by Melbournebased controls company Conserve It, the optimisation and control software solution uses feedback from its on-board real-time analytics, diagnostics, measurement and verification systems to continually re-adjust the chiller plant for optimal performance.
Two new magnetic centrifugal-type chillers are slightly larger than their predecessors, but offer high efficiency and quiet operation.
“Fortunately, the crane lifts went ahead as planned and allowed us to hit every milestone without any disruption. This was critical with the timelines we were working to. And, within two days of having the first high-load chiller operational, we had an unseasonal 30°C day in September that the low-load chillers would not have been able to cope with.” Approximately 2000kW each, the two new magnetic centrifugal-type chillers are slightly larger than their predecessors but offer high efficiency and quiet operation.
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Feature In addition to the chiller upgrade, new pumps were installed with sensors to control the variable-speed drives. The new chiller plant also features marinegrade stainless-steel pipework. The building’s heat-rejection capacity was also increased and made more efficient through the replacement and upgrade of the existing cooling towers. Temperature, flow and pressure meters were also installed on the new chiller plant to provide data to the chiller-plant control system, as well as the BMS. Works were completed overnight to avoid disruption to the building’s occupants. Plant and building conditions were carefully monitored throughout the duration of the building works to ensure minimal impact on space conditions.
MAINTAINING CONDITIONS To maintain conditions in the building during the chiller plant and cooling-tower upgrade, temporary condenser water lines were created from the generator. The control system’s intelligent optimisation was also used to produce over 1200kW of cooling from the two remaining, low-load chillers (featuring a combined nominal rating of just 1090kW). This was achieved by driving the chillers into “off design” conditions, while at the same time carefully monitoring their performance to ensure they remained within safe operating parameters. “All chillers have a design cooling rating at design conditions, but this does not mean it is the maximum cooling it can produce,” says Shah. “Typically, the BMS never tries to push the chiller to work outside the design conditions. However, the system can push the chillers to run outside of design conditions while still making sure it operates within safety limits.” By raising the chilled-water (CHW) temperature set-point and reducing the entering condenser-water temperature to the chillers, thereby reducing lift, the system was able to produce a little more cooling from the chiller than it was rated for.
In addition to the chiller upgrade, new pumps were installed with sensors to control the variable-speed drives.
According to JLL’s Hamish Stevenson, the controls software proved itself to be a critical enablement tool during the works. “Its data and reporting provision, and ability to drive performance exceeding plant capacity, enabled the project team to deliver the upgrade during less-than-ideal temperature conditions,” he says. “This was during a compressed period for both the data gathering for design, as well as overall delivery.” Since its installation, JLL’s Energy and Sustainability Services (ESS) team have also made use of the system’s data to the benefit of ANZ’s properties.
SMART SEQUENCING According to Shah, 100 Queen Street’s pre-existing BMS is now only used to initiate the chiller start-up. Once the chillers are operating, the chiller controlssystem takes full operational control of the plant from the BMS to maintain efficient operation and optimal internal temperatures. Using smart sequencing, the plant is optimised by running the most efficient combination of chillers for the given conditions, even if one of the chillers is out of service.
100 Queen’s monthly kW usage 2014, 2015, and 2016. 100 QUEEN STREET AT A GLANCE
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THE EQUIPMENT 100,000
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BMS: Schneider Chiller plant controls: PlantPRO Chillers: York Cooling towers: BAC Pumps: MASTERFLOW SOLUTIONS VSDs: Danfoss
THE PERSONNEL Building owner: ANZ Chiller plant controls: Conserve It Facilities manager: Jones Lang LaSalle (JLL) Mechanical services: Airmaster Australia Mechanical services engineer: Arup
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Feature MONITORING CONSUMPTION
Existing cooling towers were replaced and upgraded for greater efficiency.
Since completion of the main chilled-water plant upgrade at 100 Queen Street, energy consumption has been closely monitored and compared to baseline figures gathered in the year prior to the upgrade. This monitoring has revealed average monthly energy savings of approximately 30 per cent compared to the consumption under BMS control. While a reduction was expected, the results at this site have even surprised Conserve It and Airmaster. Beyond energy savings, a number of other improvements can be directly attributed to the move away from BMS control. These include reduced plant-running hours due to more accurate plant controls and more efficient CHW flow due to the control system’s ability to tune the by-pass loop more effectively.
“Once it selects the most efficient combination of chillers, it then pushes them to their sweet spots by selecting the most efficient load-point for each running chiller,” says Shah. “If a chiller operates below its nominal efficiency, it can be proactively checked by service personnel
to minimise electrical energy waste and avoid compounding service issues that can result in costly repairs.” Further energy efficiency can be achieved through advanced variable-pumping control and lift optimisation on the refrigerant side.
A reduction in chiller-staging cycles has also been realised, with more efficient staging experienced during morning peak, resulting in the chiller plant achieving and maintaining temperature set-points earlier. Additionally, a fall in temperature complaints has been recorded, supported by space condition reports. n
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