Energy Efficient Operation of Data Centres – Technical, Computational and Political Challenges

The aim of this study was to investigate the technologies and policy instruments available to improve efficiency in data centres. Data centres consume a significant and increasing proportion of the world’s electricity, and much of this electricity is consumed in cooling the computing equipment housed in these facilities. Significant potential exists to improve the efficiency of cooling in data centres. One popular method for improving efficiency in data centre cooling is to physically separate the hot and cold air streams using ‘aisle containment’ systems. This has been shown to reduce ‘bypass’ (cold air returning to the air conditioning system without having passed through any computing equipment) and ‘recirculation’ (rejected hot air returning to computing equipment inlets, leading to over-heating). However, the benefits of aisle containment have not previously been extensively quantified, nor have the optimal operational conditions been investigated. Experimental investigations were undertaken to determine the extents of bypass and recirculation in data centres employing aisle containment. Effective measures for minimising bypass and recirculation in such data centres were identified. A system model was developed to predict the impacts of this bypass and recirculation on data centre electricity consumption. The system model results showed that taking action to minimise bypass could reduce electricity consumption by up to 36%, whilst minimising the pressurisation of the cold aisles could reduce electricity consumption by up to 58%. Computational fluid dynamics models were developed to further investigate the implications of aisle containment, for both electricity consumption and cooling efficacy. Significant advancements in the techniques used to model bypass and recirculation within contained systems have been made. Finally, interviews were undertaken with data centre operators, in order to enable an assessment of the current policy environment pertaining to energy efficiency in UK data centres. Recommendations have been made for potential improvements to this policy environment.