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How ICC’s precinct-scale thermal plant works

Case study: Among the sustainability initiatives that made the International Convention Centre at Sydney’s Darling Harbour an awards and ratings magnet, a working example of a precinct-scale central energy plant is the star.

The plant provides chilled and heated water throughout the precinct, but the big design challenge was scaling the system to go from minimal load to providing comfort for tens of thousands of people during events, according to AECOM ANZ mechanical practice leader Michael Dagher.

AECOM was part of the initial Lendlease consortium that pitched for the public private partnership project, along with Capella Capital, facilities operator AEG Ogden and Spotless, the provider of facility management services.

Dagher says the challenge of the ICC, being a large precinct incorporating three major buildings and public domain, was to ensure the mechanical plant was neither undersized nor oversized.

The decision was made to use an array of six chillers, so the system could be scaled for the relevant load.

“We had to understand from the organisers and the investors when events are happening over the year,” Dagher says.

That enabled the team to develop a population profile over the year to inform decisions about the heating and cooling system design.

The number of people attending an event can vary from 5000 people to 20,000 or more, he says. In between events, the population mostlycomprises members of the public moving through the space or using areas of the public domain.

This meant configuring the plant to service very little load through to a very large one. The final plant was also configured and optimised to be able to quickly shift from low to high load, he says.

Redundancy was built in so the system can deliver comfort levels appropriate to event delegates from all around the world.

Climate change factored in

Climate change expectations were also factored in. The plants parameters anticipate for a one to two degree average rise in temperatures. The plant needs to ensure that if ambient temperatures are higher, comfort conditions within the various spaces can be maintained.

Another challenge with the design was modelling people’s movements throughout the precinct, Dagher says.

Michael Dagher, AECOM

Part of the overarching design goals for the ICC was to make the site attractive to people passing through, not just to make it a people-magnet during organised events.

A deck on top of the exhibition building has been created as public domain, along with ground plane areas and open space. The exhibition public domain can also hold large scale events.

Because a lot of the design work, including mechanical plant design, was undertaken prior to the bid, Dagher says when the contract was awarded the process mainly entailed detailing.

“We had the consultants on board, we knew the facilities manager, the event organisers and the operators,” Dagher says.

During the pre-bid period, when decisions were being made around how much of the existing Darling Harbour built form to retain and how much to demolish and replace, a lifecycle analysis costing was undertaken to guide the best way forward for the services.

Thought was also given to what kind of conditions people would expect in a world-class facility, and where plant would be located as the building envelope design took shape.

Cogeneration and trigeneration were considered, Dagher says, but because the load shifts from zero to full load, these systems were ruled out as they would have needed to be oversized compared to the average expected load.

The final solution of six chillers supplies three different mechanical ventilation, heating and cooling systems.

The theatres have displacement ventilation systems incorporating heat pipe systems for heat recovery; the exhibition building has overhead supply systems using fabric ducting; and the Convention Centre has variable air volume systems.

Energy efficiency key

Every element was designed and configured to maximise energy efficiency, Dagher says.

A substantial number of monitoring and metering devices have been installed throughout the precinct, as part of ongoing measurement and verification. These devices also enable the facility manager, Spotless, to know where energy is being used.

Ongoing optimisation has also been carried out.

The result is that after a full year of operation the system is performing “well above average”.

In terms of the coefficient of performance, the industry average for HVAC plant is between four and five, Dagher says. The ICC central thermal plant is achieving a COP of between six and seven.

The plant draws energy from the grid. As part of the carbon neutral goals for the precinct, grid power is sourced from offsite wind or solar.

Solar outperforming

The ICC as a whole also draws a percentage of its power from the Sydney Renewable Solar company’s community-owned solar array on the rooftops of the Convention Centre and the Exhibition building.

The solar going into the buildings is metered, and the resulting credits translate into a financial payback to the SRS investors.

The solar array has been performing beyond expectations. The 2017 performance report for the ICC shows that the 520 kilowatt array produced more than 655 megawatt-hours of electricity in 2017, compared to the target of 545MWh a year. It has been providing about five per cent of the ICC’s entire energy needs.

Dagher will be sharing details of the plant solution as part of ARBS 2018, which is being held at the ICC. Attendees will be able to join a site tour of the plant.

The total suite of sustainability initiatives in the precinct, including passive solar design, waste management and energy efficiency, resulted in the ICC achieving a LEED Gold rating, based on the systems as installed and performance verification. The precinct also has a 6 Star Green Star Communities rating.

In addition, in 2017 the ICC won an Master Builders Australia award for energy efficiency and project of the year from Infrastructure Partnerships Australia.

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