September 10, 2026 in News
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101 Collins Street, Melbourne
Gas Hot Water Plant Conversion to Heat Pump with Solar PV.
This innovative project in a high-profile existing building showcases a practical and achievable technology solution to improve energy efficiency and degasify to remove Scope 1 emissions in existing buildings.
This project involved the conversion of domestic hot water generation from the original building calorifiers, connected to the buildings natural gas-fired heating hot water plant, to a system featuring highly efficient commercial heat pumps, thermal storage calorifier tanks and solar PV collectors to provide off grid DC electrical energy production as the primary form of heat generation.
Separating the domestic hot water system from the central heating hot water plant enables the gas fired heating hot water plant to be able to shut down the during summer periods further reducing gas consumption, pumping energy, plant operating costs and associated plant maintenance.
A.G. Coombs Advisory was commissioned by 101 Collins Street to prepare a design and construct tender package and provide technical and installation administration services for a retrofit solution for conversion of the high-rise DHW plant. Thermal Energy Solutions provided technical input to the tender concept and were subsequently successful in being awarded the project.
A high efficiency heat pump solution reliably delivers primary DHW requirements. 8 kW of solar PV collectors were installed on the L55 roof area in addition to the existing solar PV feeding the building’s electrical supplies. The new solar PV system provides energy for supplementary heating for the 4 x 500 litre storage tanks via electric immersion heating elements.
The system is designed to integrate fully into the building’s existing systems and delivered to site as a ‘plug and play’ package ready to be assembled and commissioned.
Performance
During a 25 day test period following final commissioning the solar PV system has generated 3.78 GJ (1,050 kWh) of solar energy, and the heat pumps have delivered an estimated thermal output of 17.01 GJ (4,725 kWh) for a total thermal output of 20.79 GJ (5,775 kWh) while only consuming 5.67 GJ (1,575 kWh).
The previous plant, with convention natural gas-fired heating hot water boilers operating at 70% thermal efficiency, would consume approximately 29.7 GJ of gas to meet the same hot water demand.
During this period the new plant has reduced energy consumption by 80.91% at the plant level equating to similar reduction in associated greenhouse gas emissions.
This innovative project in a high-profile existing building showcases a scalable and practical technology solution using available technology to degasify to remove Scope 1 emissions in existing buildings while improving energy efficiency.
This project was recognised at the 2022 National Energy Efficiency Awards with the Integrated Clean Energy Award. This award recognises projects that have demonstrated excellence in integrating high levels of energy productivity and renewable energy considering aspects of performance, leadership and innovation.
For more information on this project and degasification electrification projects contact:
Jamie Park, Senior Engineer, A.G. Coombs Advisory
T: +61 3 9248 2700 | E: jpark@agcoombs.com.au
