Energy Optimization of Air-Cooled Data Centers

Abstract

The work presented in this paper describes a simplified thermodynamic model that can be used for exploring optimization possibilities in air-cooled data centers. The model has been used to identify optimal, energy-efficient designs, operating scenarios, and operating parameters such as flow rates and air supply temperatures. The results of this analysis highlight the important features that need to be considered when optimizing the operation of air-cooled data centers, especially the trade-off between low air supply temperature and increased air flow rate. The model was shown to be especially valuable in defining the optimal operating strategies for enclosed aisle configurations with fixed and variable server flows, and to elucidate the deleterious effect of temperature nonuniformity at the inlet of the racks on the data center cooling infrastructure power consumption. The analysis shows a potential for as much as an ∼58% savings in cooling infrastructure energy consumption by utilizing an optimized enclosed aisle configuration with bypass recirculation, instead of a traditional enclosed aisle, where all the data center exhaust is forced to flow through the computer room air conditioners. The analysis of open-aisle data centers shows that as the temperature at the inlet of the racks becomes more nonuniform, optimal operation tends toward lower recirculation and higher power consumption; again, stressing the importance of providing as uniform a temperature to the racks as possible. It is also revealed that servers with a modest temperature rise (∼10°C) have a wider latitude for cooling infrastructure optimization than those with a high temperature rise (≥20°C), which tend to consume less cooling power when the aisles are enclosed.

Hybrid-Cooled Data Center Server Layout Optimization for Air-Side Heat Recovery

“…Among academic studies, Kumar and Joshi [3] experimentally investigated the effect of tile air flow rate on the server air distributions located at different places in the rack. Khalifa and Demetriou [4] developed a simplified model in order to analytically determine the energy-efficient design of air cooled data centers.…”

Thermal Management of Data Centers Under Steady and Transient Conditions

“…This arrangement is popular because of its flexibility and versatility. If the layout of the server racks is changed, the corresponding perforated tile locations can be changed easily so that the cold air can be delivered to where the hot rack is located (Kang et al, 2000;Karki, 2003;Patterson, 2008;Khalifa and Demetriou, 2011;Fulpagare, 2017). Different parameters and operating conditions have been considered in the literature for a wide variety of data centers (Barroso et al, 2019).…”

“…Several data centers, spread out over the country or the world, are often available to many large organizations. It is then possible to distribute the load among data centers, depending on the environmental conditions, to minimize the power consumption (ASHRAE, 2008;Demetriou and Khalifa, 2011;Le et al, 2011;Zhang and Jaluria, 2017). Colder regions may be effectively employed in the summer and warmer ones in the winter without the extensive use of the power consuming chillers to cool the air entering the data center.…”

The Plenum concept: Improving scalability, security, and efficiency for data centers

“…With well-controlled CRAH units, server rooms with containment feature almost constant cold air temperatures within the raised floor and at any point within the contained cold air volume [11]. 1 IT outlet temperatures are a simple function of IT inlet temperature, load, and volumetric flow.…”