Performance of the variable-temperature multi-cold source district cooling system: A case study

Abstract

At present, the energy consumption and CO2 emissions of traditional building cooling systems account for a large proportion of the whole society. In this context, the district cooling system (DCS) has become an emerging green cooling solution due to its efficient and clean characteristics. However, there are many factors that affect the performance of DCS, and the changing outdoor temperature has a significant impact on the cooling load of users, and it is a challenge to set an appropriate and reasonable DCS cooling temperature operation strategy to cope with the changing outdoor temperature. This study proposed a novel operating strategy for variable-temperature cooling. An existing multi-cold source DCS operating at a constant temperature in an area with hot summer and warm winter was considered as the baseline case. Moreover, the cooling temperature of the chillers with different functions in the system was reset according to the change in the outdoor temperature, and the variable-temperature cooling model was established using the transient system simulation program (TRNSYS). Subsequently, set reasonable operating strategies for chillers and the auxiliary devices of the two models and performed the simulations. The results revealed that both models could meet the cooling load demand of users. Compared with the baseline model, the newly proposed variable-temperature cooling model reduced 18.99% of energy consumption and 19.12% of CO2 emissions, and the annual cost savings was 2.29 million RMB. Additionally, the overall efficiency of the new model increased by 15.52%.