101 Collins Street, Melbourne
- 2 days ago
- 4 min read
Project summary
Facility/application type: Commercial office building
Energy user: 101 Collins Street (Commonwealth Superannuation Corporation/101 Collins Engineering Team)
Process:
Heat pumps replacing gas boiler for space heating
Heat pumps replacing gas boiler for domestic hot water
Key benefits:
100% reduction in gas use (previously it was 9,300 GJ/year)
$230,000 annual gas costs now avoided
Electricity consumption only increased 25% and is supplemented by an on-site solar PV system
Project delivered with no downtime of available space heating for the building which occurred during a winter period
Valuable and actionable data to facility managers through building management system (BMS) integration.
Overview
101 Collins Street is a premium fifty-storey commercial office building in Melbourne’s central business district which is fully occupied with tier-one tenants.
This project involved the replacement of existing gas-fired heating hot water (HHW) and domestic hot water hot water (DHW) plants with new, high-efficiency electric heat pump systems to deliver more sustainable and future-ready heating solutions.
As part of the staged electrification of the building, first the DHW supply was separated from the HHW gas boiler and replaced with high-efficiency heat pumps (powered by an on-site direct current solar PV system) and thermal storage calorifier tanks. The DHW solution needed to meet minimum first-hour hot water demand of 1060 L to supply 132 hand washing basins and 22 service sinks over 23 levels with hygienic hot water and overcome pipework heat loss.
The mechanical solution for the HHW system was the first of this scale in a commercial retrofit in Australia. It required iterative design development and extensive collaboration between engineering, electrical and controls teams.
This solution was a cascade-type HHW system to ensure delivery of 75ºC water. It included four air-sourced heat pumps combined with two 6,000 L thermal storage tanks and connection to two water-sourced heat pumps. All new structural platforms, pipework reticulation between heat pumps, electrical switchboards and pumping systems were installed as part of the project.
Existing system
The existing system incorporated 2 x 1.8 MW gas-fired boilers to supply HHW and DHW which were installed as part of the original building construction and therefore had been operating for well beyond their serviceable life.
New solutions
Heating hot water system:
4 x 600 kW Trane air-sourced heat pumps and new low-temperature HHW circulation loop
2 x 1,600 kW Trane water-sourced heat pumps generating 75ºC heating hot water to support existing HHW loop
2 x 6,000L thermal buffer tanks
4 x new mechanical services switchboards
New submains and connection to the new main switch room
Domestic hot water system:
3 x Enermax 19 kW high-temperature commercial heat pumps
4 x Enermax 500 L SMARTcube tanks
4 x my-PV 2 kW SC20 immersion elements
8 kW solar PV array supplying DC power to the Enermax heat pumps.
The DHW heat pump units and highly insulated thermal storage tanks. Supplied by: Commercial Hot Water & Maintenance.
Challenges overcome
Providing a heat pump solution at this scale and with the desired 75ºC temperature required by the buildings heating coils for the HHW system was a challenge. The Trane product offered the best suited solution that was implemented.
The roof structure of the podium east building was never designed to cater for the installation of large air-sourced heat pumps. Careful coordination and iterative design solutions were required between the structural engineering, mechanical engineer and AG Coombs installation team.
Most electrification HHW retrofit projects are recommended to be carried out during warmer summer months when there is less heating demand. Due to equipment procurement times and gas contract alignment the project replacement landed during the cooler winter months. Careful coordination between the site facilities team, AG Coombs installation team and all the design teams was required to stage the plant change over works to have zero downtime to the buildings space heating whilst the building was fully occupied.
New Belimo energy valves were installed across all the major heating coils to ensure the pumping and heat transfer of the generated heating hot water is delivered as efficiently as possible.
The modular units for the DHW system were disassembled to bring on site and then reassembled, avoiding costly crane operations.
Project outcomes
Prior to electrification the site consumed 4,306,000 kWh/year. of electricity and 9,300,000 MJ/year of gas consumption. Post-electrification the site is consuming 5,400,000 kWh of electricity annually and no longer uses gas.
$230,000 cost savings associated with reduced gas consumption.
Energy intensity (MJ) has reduced by over 20%.
The project helps align the building with modern regulatory ESG requirements and amenity expectations of premium tenants.
The building now benefits from a significantly reduced emissions profile, market‑leading renewable‑energy credentials and improved operational efficiency, while tenants gain clearer reporting pathways and strengthened confidence in the asset’s long‑term sustainability.
The project demonstrates that complex, continuously occupied commercial towers can transition away from fossil fuels through careful planning and coordinated delivery. Its successful implementation has already informed similar large‑scale electrification initiatives and provides a practical model for decarbonising premium office assets in Australia.
"We've been very happy with the heat pumps and the move toward electrification. It has been a successful collaborative effort and has added value for tenants seeking more sustainable, future-ready buildings."
Selva Thiru, Senior Manager - Engineering, Operations and Sustainability, 101 Collins Street
Project partners
Energy user: 101 Collin Street (Commonwealth Superannuation Corporation/101 Collins Engineering Team )
Mechanical services consultant: A.G. Coombs Advisory
Mechanical services contractor: A.G. Coombs Projects
Electrical services consultant: Compass
Electrical contractor: Brolec
Building controls: Techstream Systems/Trane Australia
HHW heat pump solution provider: Trane Australia
DHW heat pump solution designer: Commercial Hot Water & Maintenance
DHW heat pump solution provider: Commercial Hot Water & Maintenance
