CASE STUDY: HVAC cooling via seawater heat exchangers for Walsh Bay Wharfs 4/5, Sydney

KEY INFO

Customer: Infrastructure NSW

Year completed: 2020

Location: Walsh Bay Wharfs, Sydney

Facility type: Heritage-listed performing arts precinct

Process type: Building cooling via close-loop seawater heat exchange (HVAC)

Technologies used: Close-loop seawater cooling system using titanium plate heat exchangers – the first use of this technology in Australia

Architect: Tonkin Zulaikah Greer

Builder: Richard Crookes Constructions

Geothermal consultant: GeoExchange Australia

Geothermal contractor: TFG

Geothermal project manager: Flexigen

Mechanical services engineer: Fredon Air

Project benefits:

• Approximately 555 tonnes CO2 avoided annually

• No water consumption (closed loop)

• Energy saving particularly during peak periods

• Elimination of Legionella risks and rooftop corrosion

• Reduced long-term maintenance burden

Project summary:

Flexigen was engaged as geothermal project manager for the Wharf 4/5 redevelopment at Walsh Bay - a $207 million transformation of a State Heritage-listed maritime wharf into a world-class performing arts home for six of Australia's leading arts organisations, including Sydney Theatre Company, Bangarra Dance Theatre and Sydney Dance Company.

Working alongside GeoExchange Australia, Flexigen helped deliver Australia's first closed-loop seawater cooling system using titanium plate heat exchangers, providing energy-efficient, heritage-compliant HVAC across 13 new theatres, studios, and rehearsal spaces constructed within the 100-year-old ironbark timber wharf.

Flexigen's project management ensured alignment across environmental assessment, engineering design, heritage compliance, and construction - coordinating a technically demanding programme carried out entirely over water between October 2018 and November 2020.

The challenge being addressed by the project:

Wharf 4/5 required a high-performance cooling solution capable of serving world-class performance spaces, while meeting the strict conditions of a State Heritage listing. Infrastructure NSW had experienced maintenance problems with open-loop systems on previous projects and sought a closed-loop alternative, while heritage requirements ruled out conventional rooftop cooling towers entirely.

Construction was further complicated by the wharf's over-water location - deliveries were made by barge or helicopter, machinery was adapted to meet strict weight load limits on the wharf structure, and vehicular access was limited to single-axle trucks travelling in one direction.

Existing system: 

Prior to redevelopment, Wharf 4/5 had no HVAC infrastructure suitable for performing arts use at scale. Earlier comparable waterfront projects in Sydney - including the Wharf Terraces at Woolloomooloo and the Sydney Water Police station - had used polyethylene coil systems, but these were unsuitable at Walsh Bay due to the larger installation area required and the difficulty of fitting them between the site's non-uniform pylons. 

The solution deployed:

GeoExchange Australia was engaged from 2012 in the project's early design phase to assess the suitability of a closed-loop seawater system. Walsh Bay's water depth (roughly 2 - 3 metres), safe pylon environment, and the thermal capacity of Sydney Harbour - with tidal flows preventing heat plume buildup - all confirmed the site's suitability.

Infrastructure NSW commissioned Jacobs to conduct a harbour heat rejection impact assessment in 2017, including thermal plume modelling, which found environmental risk to be insignificant. Flexigen coordinated this multi-year regulatory and engineering process through to the successful installation and commissioning of the titanium plate heat exchanger system beneath Wharf 4/5.

Other supporting measures in the project:

• Passive design targeting 30% reduction in energy demand

• Adaptive reuse of heritage building fabric to reduce embodied energy

• Rainwater harvesting supplying 100% of non-potable water needs

Project outcomes:

The seawater cooling system delivers consistent energy savings - particularly during Sydney's peak summer cooling periods while eliminating the operational and compliance risks of open-loop systems. Combined with the rooftop solar array, Wharf 4/5 now avoids approximately 555 tonnes of CO2 annually. The project has established a replicable benchmark for renewable thermal energy in heritage waterfront buildings across Australia.

Project observations and challenges:

Spanning nearly a decade from early feasibility (2012) to completion (2020), the Wharf 4/5 project demanded sustained, trust-based collaboration across a large and diverse project team. Flexigen's role as geothermal project manager was pivotal in maintaining continuity and coordination across the environmental, engineering, heritage, and construction workstreams, particularly given the pioneering nature of the titanium plate heat exchanger technology and the challenging over-water construction environment.