Thermal equity, public health and district cooling in hot climate cities

摘要

In urban environments, 'chemical' air pollution has long been of concern. Currently, 'physical' air pollution, in the form of excessive temperatures, is likely to impact public health even more, especially in cities with hot climatic conditions. The urban heat island effect (UHI) - whereby big-city air temperatures are already elevated by up to 7℃ - is intensifying with urban growth and global warming. Overheating of cities is in addition inequitable, as it is predominantly caused by the rich and suffered by the poor. Heat waves are becoming more frequent and severe. Measures to combat UHI include improved urban design, improved technical efficiencies, reduced heat from vehicles, reduced consumption and palliative or emergency civil measures. A measure of exceptional interest is 'district cooling' (DC), the counterpart of the district heating widespread in temperate climates. DC offers economies of scale, higher-energy efficiency than air conditioning, lower climate emissions and other benefits. It is in fact almost the only way to actually counteract UHI, by removing heat from the urban environment, thus reducing the growing energy use and health impacts in hot climate cities. This paper surveys the current practice in DC and its potential benefits.