Evaluation of Air-Side Economizer Use in a Compute-Intensive Data Center

Moore’s Law continues to drive increased compute capability and greater performance per watt in today’s and future server platforms. However the increased demand for compute services has outstripped these gains and the energy consumption in the data center continues to rise. The challenge for the data center operator is to limit the operational costs and reduce the energy required to run the Information and Communications Technology (ICT) equipment and the supporting infrastructure. The cooling systems can represent a large portion of the energy use in the support infrastructure. There is significant focus in industry today on applying advanced cooling technologies to reduce this energy. One potential solution is the use of air-side economizers in the cooling system. This technology can provide a reduction in cooling energy by being able to maintain the required temperatures in the data center with the mechanical refrigeration turned off, significantly reducing the PUE for the data center. This paper reviews recent industry activities around the recommended environmental conditions in the data center, the impact to the ICT equipment of air-side economizers, where they can best be applied, and provides data from a case study recently concluded at Intel’s site in New Mexico. In that case study servers from an engineering compute data center were split into a standard configuration (closed system, tight temperature control) and a very aggressive air-side economization section (open system, significant out-door air quantities, moderate temperature control). Both sections performed equally well over a year long on-line test, with significant energy savings potential demonstrated by economizer side. The American Society of Air-conditioning Heating and Refrigerating Engineers (ASHRAE) has recently published new ICT-vendor consensus-based recommendations for the environmental conditions in data centers. These new limits are discussed in light of the successful experiment run in New Mexico as the revised operational envelop allows a far greater number of hours per year when a data center can be run in “free-cooling” mode to obtain the energy savings. Server design features as well as lessons learned from the experiment and their applicability to the potential use of air-side economizers is also discussed.