Influence of Air-Conditioning Waste Heat on Air Temperature in Tokyo during Summer: Numerical Experiments Using an Urban Canopy Model Coupled with a Building Energy Model

TLDR

A coupled urban canopy and building energy model was developed to study diurnal outdoor temperature variations in Tokyo office districts. The coupled model integrates a multilayer urban canopy model with a building energy analysis model and was applied to two Tokyo office areas through observations and numerical experiments. The model accurately reproduces weekday and holiday temperatures, showing that building waste heat is negligible, whereas air‑conditioner waste heat raises weekday temperatures by 1–2 °C and contributes to Tokyo’s heat‑island effect.

Abstract

Abstract A coupled model consisting of a multilayer urban canopy model and a building energy analysis model has been developed to investigate the diurnal variations of outdoor air temperature in the office areas of Tokyo, Japan. Observations and numerical experiments have been performed for the two office areas in Tokyo. The main results obtained in this study are as follows. The coupled model has accurately simulated the air temperature for a weekday case in which released waste heat has been calculated from the energy consumption and cooling load in the buildings. The model has also simulated the air temperature for a holiday case. However, the waste heat from the buildings has little influence on the outdoor temperatures and can be neglected because of the low working activity in the buildings. The waste heat from the air conditioners has caused a temperature rise of 1°–2°C or more on weekdays in the Tokyo office areas. This heating promotes the heat-island phenomenon in Tokyo on weekdays. Thus, it is shown that the energy consumption process (mainly with air conditioning) in buildings should be included in the modeling of summertime air temperature on weekdays in urban areas.