Critica factors in adopting cooling media for central air-conditioning systems in Hong Kong

There has been a dilemma about whether to adopt water-cooled or air-cooled air-conditioning systems at various times for different developments in Hong Kong, strongly influenced by the local government. Fresh water has been a scarce resource as a cooling medium; however, in recent years, the local government has advocated water-cooled air-conditioning systems, using fresh water or sea water as a cooling medium in the condenser units. Although such water-cooled air-conditioning systems use less energy than air-cooled systems, they can be potentially harmful to the environment and end users if not adequately designed and maintained. There are obvious pros and cons to both systems. Moreover, sea water as a cooling medium has its limitations if one expects to achieve more sustainability, inevitably at a higher initial cost compared with other systems. In this research, detailed studies are carried out on water-cooled and air-cooled air-conditioning systems in buildings in Hong Kong, aiming to achieve more sustainable design while comparing the cost implications of adopting an appropriate system or converting an existing system. In addition, the government's water supply policy, operation theory of water-cooled and air-cooled condenser units, environmental implications, difficulties in conversion and professionals' opinion are explored. Major stakeholders such as developers, facilities managers, engineers, surveyors and architects could benefit from this research into air-conditioning systems with respect to fulfilling further sustainability criteria and providing environmental protection at optimal costs. This research will be useful in sustainable green building design and also in reducing energy consumption and adverse environmental impacts such as global warming, air pollution and climate change.