Annual Energy-Carbon Characteristics and Efficiency Evaluation of an Integrated Cooling and Waste-Heat Recovery System in Data Centers

Waste-heat recovery and utilization represent key technological pathways for promoting the low-carbon development of data centers. A comprehensive analysis of annual energy consumption and carbon emissions， coupled with a rational evaluation of system-level efficiency， is essential for advancing the integrated utilization of data-center resources. This study focuses on an integrated cooling and waste-heat recovery system in data centers and proposes two evaluation indicators from the perspectives of energy and carbon emissions： general exergy efficiency， ηGEX and general carbon efficiency， ηGOC . The proposed indicators are validated using simulation data. The results indicate that the general exergy efficiency metric effectively evaluates data center integrated systems. Specifically， the system in Lhasa achieves the highest general exergy efficiency of 29.27%， whereas the lowest general exergy efficiency （23.65 %） is observed in Harbin. The general carbon efficiency indicator enables a quantitative assessment of the carbon-reduction potential achieved by replacing conventional heating systems integrated with data centers. Depending on the type of displaced traditional heating technology used， the general carbon efficiency in Lhasa ranges from 3.75 to 4.45. Overall， the proposed evaluation framework provides a robust and rational basis for assessing the operational efficiency and carbon-mitigation potential of data center integrated systems， offering valuable guidance for their practical deployment and retrofitting in modern data centers.