District cooling systems: Technology integration, system optimization, challenges and opportunities for applications

District cooling system (DCS) has been widely used because of its low cost and high energy efficiency. Excessive studies have been done on DCSs, based on either actual projects or hypothesis. This paper presents a comprehensive review on the research and applications of DCSs. The characteristics and problems of DCS are introduced. The performance and progress of DCS integrated with sustainable energy technologies are summarized, including systems integrated with renewable energy systems, combined cooling, heating and power systems, and thermal storage systems. Efforts on the optimization of DCS are reviewed and categorized, including the efforts on district planning, DCS design, operation and control. An introduction on the existing typical DCS projects in China is presented. Challenges and opportunities for future application of DCS are discussed including the uncertainty issues at design stage, the control optimization and integration with smart gird.