Examining Perth’s Climate Trends: A Temporal Analysis and the Implications for Building Performance and PV System Simulations

As part of the ongoing investigation into our evolving climate, we routinely process and analyse meteorological data from successive years, conducting comparative assessments to reveal emerging trends and patterns.

Our previous temporal analyses only focused on examining variations in various weather elements. However, in this latest iteration, we have incorporated the results of EnergyPlus simulations, specifically targeting HVAC systems and heating and cooling dynamics within buildings. We have also added the results of System Advisor Model (SAM) photovoltaic (PV) system simulations to enhance the comprehensiveness of our investigation.

The most recent temporal analysis was carried out for all eight capital cities, though this issue of Exemplary Advances will focus on the city of Perth. The findings for Hobart were previously discussed in the July issue of Exemplary Advances. The analysis for other capital cities can be viewed here.

For the analysis of weather elements, we examined the temporal variations in dry bulb temperature, humidity, wind speed, global horizontal irradiation (GHI), direct normal irradiation (DNI), and total precipitation. The analysis involved averaging these elements over three 15-year periods—1990-2004, 2005-2019, and the latest 15-year period from 2009 to 2023—and then comparing the results. A comparison between data from the latest 15 years, the data corresponding to the years and months specified in Industry Standard Meteorological Year (ISMY) files, and the data exclusively from 2023 was also undertaken. ISMYs were originally developed for application in house energy rating software used in NatHERS and derive from historical Bureau of Meteorology (BOM) weather data spanning from 1990 to 2015. Over time, they have become the industry’s de facto standard. It is therefore important to compare against ISMY data, as it provides a reference to gauge alignment with established benchmarks and understand the significance of temporal variations in weather elements.

Comparing 1990-2004 with 2009-2023 showed an increase in Perth’s mean temperature of 0.51°C, a decrease to moisture of 0.62%, and an increase in wind speed of 16.02%. GHI had an increase of 2.58% and DNI had an increase of 1.03%. Meanwhile, comparing 2005-2019 with 2009-2023 showed an increase in the mean temperature of 0.22°C, an increase to moisture of 0.14%, a comparably increase in wind speed of 0.72%, and an increase in GHI and DNI of 0.84% and 0.39%, respectively. The incline in mean temperature, GHI, and DNI for 2005-2019 vs 2009-2023 is likely a result of 2020-2023 experiencing comparatively lower annual average dry bulb temperatures, GHI, and DNI when compared to other years.

Total precipitation in 2009-2023 averaged 11.18% less than in 1990-2004. However, compared to the 2005-2019 period, it saw a 1.63% decrease.

The annual energy consumption trends reveal intriguing patterns across various building archetypes. From 1990 to 2023, all archetypes exhibited increasing trends in both cooling and total energy consumption, with consistent rises during the 15-year periods of 1990-2004 and 2005-2019, but a shift to decreasing trends from 2009 to 2023. In contrast, heating energy consumption generally showed decreasing trends from 1990 to 2023, as well as during the periods of 2005-2019 and 2009-2023, though patterns varied among building types. For instance, 3-storey and 10-storey office buildings experienced increasing trends from 1990 to 2004, while supermarkets showed the opposite, with decreasing trends during the same period. These patterns suggest a warming climate, underscoring the importance of using climate data from the more recent 2009-2023 period in building energy simulations, rather than relying on older ISMY data.