Comparison of Approaches for Calculating Annualized Data Center Energy Metrics

摘要

Calculation of the annualized Mechanical Load Component (MLC) and Power Usage Effectiveness (PUE) of a data center requires determining the annual facility energy consumption in kWh. For this purpose, ASHRAE Standard 90.4 recommends running an annual simulation for 8760 hours using an hourly timestep. The Standard also allows an annualized metric calculation by running a simulation with external temperature values placed into bins with a 1℃ (2℉) increment. However, the influence of bin size in the latter approach on the calculated annualized MFC and PUE is unknown. Therefore, this paper examines the influence of bin size on these energy metrics for four commonly-encountered climate conditions in the US. The results of this work show that the calculated metrics are essentially independent of bin size. A. minimum bin width limit of 0.5-0.75℃ (0.9-1.35℉) is seen for all four locations where non-continugous bins occur due to the hourly discretization of annual weather data. A maximum bin width limit also exists that results in nonphysical psychrometric conditions for the chosen binning method, and this limit is location-dependent since these nonphysical conditions occur near saturation conditions.