Improved energy management of chiller systems with data envelopment analysis

The operation of chiller systems could take up over half of the electricity consumption of air-conditioned buildings in subtropical regions. This paper explains how to examine the effectiveness of their energy management by using data envelopment analysis (DEA). A large-scale system with seven chillers of two different capacities was studied. The scale, technical and overall efficiencies defined in DEA were calculated for each set of operating conditions comprising the system coefficient of performance (COP) and input variables: the compressor power, chiller load and temperatures at the evaporator and condenser sides. Under the existing operating strategy, the average system COP was found to be 5.73 with an average technical efficiency of 0.97. This indicates that the system operated very efficiently for most of the time. Fine-tuning the temperature-related controllable variables could achieve the highest possible COP of 5.83 with technical efficiency of one. The benefits of using technical efficiency to identify energy management opportunities are highlighted.