Our cities and outdoor spaces are facing the Urban Heat Island phenomenon and the overheating due to climate change during summer season. Urban heat island (UHI) and global warming increase the near surface ambient temperature in cities. Urban heat island can affect the energy performance of buildings located in densely built areas as these buildings undergo several UHI effects such as higher external air temperatures, lower wind speeds and reduced energy losses during the night period.
The specific objective of the study is to propose, investigate, and optimize the combination of advanced thermal mitigation and smart technologies to improve thermal comfort and mitigate the urban overheating in the area.
The following activities have been carried out:
- Aerial monitoring of the surface temperatures using drone technologies and the mobile Energy Bus to measure the temperature distribution in the whole area by employing multiple measurement techniques (A terrestrial survey and an aerial survey).
- Identification of the climatic conditions and hot spots in the area and development of preliminary mitigation scenarios. This investigation has been built on two different simulation approaches for analysis: microscale modelling and Mesoscale modelling.
- Preliminary climatic evaluation of the proposed mitigation scenarios (10 scenarios in three different conditions: Mean maximum, heatwave and winter conditions) and final selection of the technologies and systems to be implemented.
- Detailed thermal study and optimization of the proposed mitigation scenarios.
The impacts of different mitigation technologies were assessed in three different conditions: Mean maximum, heatwave and winter conditions. The results have shown that:
- The maximum reduction of ambient temperature achieved under combined scenario (scenario 6: cool pavement, greenery, shading, spray system, and cool roof) is 6.4°C, 6.7°C, 4.4°C during mean maximum, heatwave and winter conditions, respectively.
- The maximum local air temperature reduction ranges between 0.3°C for cool roof and 6.4°C for the combined scenario during mean maximum condition, between 0.2°C for cool roof, and 6.7°C for the combined scenario during heatwave condition, and between 0.2 °C for cool roof, and 4.4 °C for the combined scenario during winter conditions.
- Under the mean maximum condition in summer, cool pavement, shading (solar control), water technologies (misting system), and combination of different strategies are the most effective solutions to improve comfort in Phillip St.
- The average air temperature reduction reaches to 1.3°C for the combined scenario during mean maximum and heatwave conditions.
- By applying combined scenario during mean maximum condition, the average, maximum and minimum air temperature may be reduced to 31.3 °C, 33.2 °C, and 29.2 °C, respectively.
- Water has strong local effect and lead to a maximum reduction of 5.1°C, 5.4°C, 4 °C during mean maximum, heatwave and winter conditions, respectively.
- After application of the combined scenario, the surface temperature in Phillip Street mostly falls below 32°C, between 31.9°C and 48.7°C, and between 22.5°C and 10.5°C during mean maximum, heatwave and winter conditions, respectively.
- From the comfort analysis, Philip St. presents from a moderate to very strong heat stress under the mean maximum condition in summer and from a very strong to extreme heat stress under the heatwave condition.
- The Universal Thermal Climate Index (UTCI) is ranging from 38-40°C and PET is consistent with UTCI indicating areas out of comfort range (mostly varies from about 40°C to 46°C) during mean maximum condition. After application of the combined scenario during the heatwave condition, UTCI and PET mainly varied from about 38°C to 45°C and 39.1°C to 48.4°C, respectively. Phillip Street indicates no heat stress with UTCI and PET mostly falling below 27.4°C during winter condition.
Distribution of comfort indices in the City of Parramatta CBD and Phillip St: Scenario 6, winter condition.
Project Leader: Scientia Prof Mattheos Santamouris and Dr Gloria Pignatta
Research team: Dr Shamila Haddad, Dr Riccardo Paolini, Dr Carlos Bartesaghi Koc, Marco Brozzetti, Samin Marzban, Jie Feng, Kai Gao.