A holistic study of the WLCG energy needs for the LHC scientific program

Abstract

The WLCG infrastructure provides the compute power and storage capacity needed by the Large Hadron Collider (LHC) experiments at CERN. The infrastructure is distributed across over 170 data centres in more than 40 countries. The amount of energy consumed by the WLCG to support the scientific program of the LHC experiments, and its evolution, depends on different factors: the luminosity of the LHC and its operating conditions; the data volume and the data complexity; the evolving computing models and the offline software of the experiments; the ongoing R&D program in preparation for the next LHC phase (HL-LHC); the evolution of computing hardware technology towards better energy efficiency; and the modernization of the facilities hosting the data centres to improve Power Usage Effectiveness. This contribution presents a study of the WLCG energy needs and their potential evolution during the future LHC program based on the factors mentioned above. Some of the information is obtained from the CERN experience but then extrapolated to the whole of WLCG. The study provides, therefore, a holistic view for the infrastructure rather than a detailed prediction at the level of the individual facilities. It presents a clear view of the trends and offers a model for more refined studies.