The Heat Square: visualising urban microclimate phenomena in a small scale controlled urban environment

Abstract

Urban microclimates have a great impact on the thermal comfort of city inhabitants, with the Urban Heat Island (UHI) and the Subsurface Urban Heat Island (SUHI) effects posing a growing challenge under the accelerating impacts of climate change. This thesis focuses on investigating the UHI and SUHI effects and exploring potential mitigation strategies within a controlled urban environment, specifically the ”Heat Square” at The Green Village in the Delft University of Technology. The Heat Square serves as an experimental urban environment designed to analyse various urban cooling measures. To capture the spatial and temporal variations in soil temperature within the Heat Square, Distributed Temperature Sensing (DTS) technology was deployed. DTS measures high-resolution temperature data, which allows for detailed analysis of the soil temperature response to different cooling scenarios, including the implementation of green infrastructure, shading, and reflective surfaces. These in-situ measurements were then compared with urban microclimate modeling results using ENVI-met, a Computational Fluid Dynamics (CFD) tool for modeling urban microclimatic conditions. ENVI-met, along with other urban microclimate models, can predict the impact of urban design on local temperature and thermal comfort indices. The findings of this research highlight the significant potential of green infrastructure and shading as effective strategies to mitigate the UHI effect. Specifically, the introduction of vegetation and shading elements resulted in noticeable reductions in both surface and air temperatures as well as Mean Radiant Temperature (Tmrt) within the urban environment. These findings were supported by performing simulations of different urban scenarios of the Heat Square. However, the study also highlighted challenges in accurately modeling urban microclimates, as shown by discrepancies between the DTS measurements and ENVI-met simulations. These differences suggest the need for further refinement of model parameters to better approximate the complexities of real-world urban environments. Overall, this thesis contributes to the broader understanding of urban cooling measures and their role in enhancing the resilience of cities to climate change. The insights gained from this research are intended to inform urban planning and design practices, promoting the development of more sustainable and climate-resilient urban spaces as well as the applicability of urban microclimate monitoring tools. Future research should focus on refining the ENVI-met model of the Heat Square to enhance its accuracy in properly simulation real-life responses of the urban environment to climatic variations. Additionally, exploring a broader range of urban cooling strategies, including water-based solutions and varying surface materials, could broaden knowledge on heat mitigation strategies. Studying soil thermal responses in other urban environments with DTS would also be valuable for studying indirect effects of the SUHI effect. Collaborations between researchers, urban planners, and policymakers are important to ensure that scientific findings are translated into practical applications that increase climate adaptability of urban environments.