PS 43-84 - Simulation of the thermal effect of greening on urban area

Background/Question/Methods

Urbanization is progressing around the world and the phenomenon of urban heat islands, where the temperature of cities increases compared to the surrounding areas due to climate change, is intensifying. Many strategies are being applied to alleviate urban heat islands, and one of them is urban greening. Urban green areas form shadows to block solar radiation, or change the rate of reflection and emission of heat caused by changes in surface environment. It also has the effect of reducing the surface temperature by increasing latent heat through the evapotranspiration occurring in the leaves. Representative urban greening strategies are street trees, green roof, and green wall. Since the cooling effect varies greatly depending on the weather environment, size of green space, and installation location, it is challenging to estimate the cooling effect that changes according to various environments. In this study, a three-dimensional urban canopy model was developed to evaluate the effects of various green spaces.

Results/Conclusions

This model, which simulates the copy transfer process between urban elements, first builds a domain consisting of squares of a certain size and calculates the view factor and the sky view factor. Next, the short-wave radiant heat and the long-wave radiant heat are simulated to calculate the net radiation. And the net radiant heat is partitioned into sensible heat, latent heat, and storage heat. Finally, the thermal effect of the green wall, green roof and street tree on the surrounding environment was simulated. Street trees greatly improve the thermal environment of the walking space, so it could provide a great cooling effect for pedestrians. On the other hand, the green wall and the green roof did not significantly affect the walking space, but it can greatly reduce radiant heat entering the building, which soon saves cooling energy and reduces artificial heat derived from the building. This model can be used for efficient green space planning to reduce urban heat.