Modelling of building integrated photovoltaic thermal system to achieve net zero energy in a benchmark high-rise building across Australian climates

: The Australian government aims to achieve net-zero greenhouse gas emissions by 2050. Amongst various sectors, reducing emissions from the building sector is crucial. Buildings account for 50% of Australia’s energy consumption and 20% of its greenhouse gas emissions. While achieving net-zero in single- or double-storey residential buildings is straightforward, in high-rise structures it is particularly difficult due to limited roof space for deploying on-site renewables. The study models building integrated photovoltaic thermal (BIPV/T) systems in a 12-story office across seven Australian cities using Rhinoceros 3D (EnergyPlus engine). The simulations consider simultaneous electrical and thermal energy generation. The results show that BIPV/T systems deliver an absolute electrical efficiency gain of 3.5–4.5% compared to BIPV across all climates, peaking at 16.9% in Melbourne. Thermal energy output, ranging from 2.7 to 3.3 GWh from rooftop systems, accounts for most total energy yield, while electrical generation alone satisfies only 6–19% of building energy demand. Net-zero is achieved in Perth, Sydney, and Melbourne via rooftop & façade BIPV/T. Adelaide, Brisbane, and Canberra achieve >0.85 energy balance, but Darwin lags (energy balance 0.38) due to hot-humid climate limitations. Overall, a site energy balance approaching or exceeding 1.0 in several cities confirms the potential of BIPV/T systems for net-zero performance when both electrical and thermal outputs are effectively harvested. While effective harvesting of electrical energy is easy, thermal energy harvesting efficiency depends on the optimised design and operation of thermal systems, including thermal storage tanks, heat-pumps, pumps, adsorption chillers, heat exchangers and air/water flow rates, etc.