District Cooling: A Key Solution for Hot Climate Cities

Abstract

This chapter addresses energy solutions at the urban scale, principally though not uniquely for cooling. Whilst district heating (DH) systems are widespread, district cooling (DC) is less well known, although DC systems have existed for some years in both hot-dry and in hot-humid climates. There are major efforts today to spread awareness of DC, not least in Asia. After a brief overview of the development worldwide and scope of district energy systems, we focus on Malaysia, which is a leading example. We also highlight a little discussed conflict between the level of individual buildings versus that of urban energy planning. Which level should be prioritised and under what conditions?

In the rapidly growing cities of developing countries, millions are moving to dense urban environments, often of mediocre quality and with few or any energy-efficiency measures. Temperatures are typically 2-4 degrees hotter in inner city areas, and rising. The fraction of the world’s 30 largest cities that lie in the tropics is forecast to rise from 40 % in 2000 to 60 % by 2025 (UN, World urbanisation prospects: The 2014 revision. New York, UN, 2014). Typically, heat from vehicles accounts for between 20–30 % of the anthropogenic sources of heat in large cities, whilst the energy use in buildings accounts for 60–75 % (Stewart and Kennedy, Estimating anthropogenic heat release from megacities. In ICUC9—9th International Conference on Urban Climate held jointly with the 12th Symposium on the Urban Environment, July 20–24, 2015, Toulouse, France University of Toronto, Toronto, 2015). The common cooling solution is still small-scale air conditioning (AC) units in individual buildings. Each one exhausts heat to the outdoors, hence heating up the city even more. Thus, ironically, cooling is itself one of the major causes of heat in the city. In addition, small AC units are inefficient, not always healthy, and expensive to run. Larger urban scale solutions offer much higher technical efficiency as well as advantages as to energy sources, costs and management. And not least, district energy solutions offer one of the only ways to counteract the urban heat island (UHI) effect.

Better technology can help, but the fundamental challenge is to remove the sources of heat from the city. This is what DC systems offer; the unique feature of reducing UHI, thus impacting positively on environment as well as on comfort and public health. District cooling is a key to future urban planning and energy policy in hot climates.