Evaluating urban vegetation scenarios to mitigate urban heat island and reduce buildings' energy in dense built-up areas in Cairo

Abstract

Cairo is characterized by high temperature compared to its surrounding areas, especially during the summer time. This effect is strengthened by the widespread use of sealed surfaces and the lack of vegetation. Therefore, the consumption of electricity in indoor spaces for cooling purposes is a critical problem especially in the summer time. The use of air conditioners has increased during the last 10 years enormously. Because of this, electricity bills increased in a huge way, which represents a burden on the citizens. Therefore, this study aims to find unconventional solutions for the reduction of energy through mitigating urban heat island (UHI) and enhancing thermal performance in Cairo.This paper studies various area cover factions of trees in an urban environment, which can be used to mitigate UHI, improve thermal performance in outdoor spaces and reduce energy consumption in high dense built up areas in Cairo. A small area of 250 m * 250 m from downtown Cairo was simulated as a case study using ENVI-met V.4.3.2. The comparison between reference scenario and suggested scenarios, which are 30% trees, 50% trees and 30% trees +70% grass, were conducted on a summer day in Cairo. The outputs were used to estimate the amount of energy in every scenario using DesignBuilder model. The results show that the scenario with 50% trees led to the best human thermal comfort (3 K cooler). Although for the demand of energy in the buildings, the street orientation as well as the aspect ratio (H/W) play an important role and should be considered.