Brimbank Aquatic and Wellness Centre Integrated Energy System – Performance analysis

Key performance aspects discussed in the report include:

• Technical Feasibility: The all-electric building services solution is considered technically feasible. The backup gas boiler contributed only 1.8% of the total thermal energy injected into the field during the first 12 months, indicating the heat pump arrays are largely sufficient.
• Commercial Feasibility: The all-electric solution is commercially feasible, with a simple payback period of 7.4 years compared to a Business-As-Usual (BAU) hybrid thermal plant. This payback period reduces to 5.4 years when accounting for carbon offset costs.
• Coefficient of Performance (COP): The 4-pipe heat pump’s COP/EER was found to be around 3. While this figure is far better than what would be achieved with a conventional gas system, it could be improved by updating the control strategy to utilize the waste heat effectively.
• Energy Performance Comparison: The BAWC’s facility-wide Energy Use Intensity (EUI) is 38% lower than a similar established all-electric facility, mainly due to an industry-leading building envelope and an open balance air distribution system.
• Low-Grade Heat Applications: The BAWC operates at low flow and return temperatures (53∘C/45∘C), which is ideal for heat pump efficiency (higher COP).
• Performance Risks in Cooler Climates: The heat pump array is designed to serve thermal loads at Melbourne’s design conditions (3.5∘C ambient). Risks like decreased efficiency at low temperatures and interrupted operation due to defrost cycles are addressed by sufficient heat pump capacity, staging of the array, and the incorporation of thermal energy storage.
• Building Envelope Impact: A more conventional building envelope would increase the required thermal capacity for heat pumps, leading to larger equipment and increased capital costs.
• Thermal Storage Design Issues: The round-trip efficiency of the Thermal Energy Storage (TES) at BAWC is low, with only 13% of charged energy available in August 2024. The current series arrangement of the four thermal storage tanks is inefficient due to turbulence and poor thermal stratification. Modifying pipework to operate tanks in parallel plus adding multiple temperature sensors may result in better outcomes.
• Power Purchase Agreement: A key feature of BAWC is that the power used in the centre comes from a combination of rooftop solar and renewable electricity sourced through the Victorian Energy Collaboration Power Purchase Agreement.