An improved use of cooling degree-days for analysing chiller energy consumption in buildings

Cooling degree-days have not commonly been used in building energy analysis due largely to a lack of understanding of how they should be defined. The extra complexity of cooling systems, including the existence of latent loads, means that simplified energy analysis techniques have been deemed too crude to be meaningful. This paper presents a detailed analysis of measured cooling energy data from a large air-conditioned site in Perth, Western Australia, which builds on previous theoretical work to develop a robust definition of cooling degree-day base temperature. The results show that not only do cooling degree-days give results suggested by the theory, but that the use of cooling energy performance lines can be used for more sophisticated energy analysis. Practical application: The energy performance of buildings is becoming increasingly important to define. Energy monitoring and analysis techniques using degree days have usually been confined to heating systems. This paper sets out how cooling degree-days can be used to assess the operational performance of a refrigeration plant, using real data to demonstrate the potential of the method.