Evaluation of the impact of the urban heat island on residential and commercial energy consumption in Tokyo

This study evaluated the impact of the urban heat island (UHI) in the Tokyo metropolitan area on energy consumption in the residential and commercial sectors. Although there are many indications that UHIs increase energy consumption by air conditioners, the possible decrease in consumption of heating energy in winter is usually ignored. To quantify the net impact of a UHI, it is crucial to consider both factors. Furthermore, it is important to consider the spatial distribution because a UHI represents the local temperature change in an urban area, and the spatial distribution of energy consumption in an urban area is complicated. We developed a new method to evaluate UHI impact by taking into consideration the spatial and temporal distributions of both energy consumption and air temperature. The results reveal that the UHI increases commercial energy consumption in the Tokyo metropolitan area but decreases residential energy consumption; however, there is a total net decrease in energy consumption. This suggests that UHI mitigation measures should particularly target the city center, where commercial buildings are concentrated, whereas in residential areas, sufficient assessments must be conducted to ensure that mitigation measures are introduced with caution. (C) 2011 Elsevier Ltd. All rights reserved.