Chiller system performance benchmark by data envelopment analysis

The operation of chiller systems could account for the major proportion of electricity consumption in commercial and industrial facilities. This paper considers using data envelopment analysis (DEA) to facilitate benchmarking their energy performance. A system serving an institutional building was studied, which contains five sets of chillers, pumps and cooling waters. The scale, technical and overall efficiencies defined in DEA were calculated based on the correlation between the output - system coefficient of performance (COP) - and the inputs - load factor and temperatures of chilled water and condenser water. Results of DEA indicated that the existing operating strategy gave an average technical efficiency of 0.85 and fine-tuning the temperature-related variables could improve the average system COP from 3.87 to 4.56 - the highest possible performance with technical efficiency of one. The significance of this study is to demonstrate how DEA helps rectify control and operational problems of chiller systems and to estimate their highest achievable performance.