Data center cooling
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The goal of this thesis was to examine possibilities to improve energy efficiency of data center cooling. Data centers form the ground for the telecommunication business. Energy consumption of the data centers is already globally significant because data centers consumed 1.1-1.5 % of world’s electricity use in 2010, and about 40 % of that is used for cooling. Enhancement of the data center cooling has a good potential to reduce energy consumption, greenhouse gases, and costs of telecommunication. This thesis is divided into two parts. The first part will offer a basic theoretical background for the data centers and their cooling systems as well as issues related to thermal management of data center. The second part consists of case study made for Finnish data centers locating part of the office building. Power usage effectiveness (PUE) were inspected and evaluated for the data centers of the building. The close liquid cooled system were compared to the traditionally air cooled system using measurements. Air flow problems at the data centers were discussed. The effects of free cooling and district cooling to the cooling system and energy consumption were discussed. PUE-value of the examined building varied between 1.2 and 1.8. Comprehensive, real-time and partial monitoring of PUE is demanding, but inserting a few fixed measurements, PUE-value can be defined. Using close liquid cooling, the power density of IT equipment can be higher than with traditional air cooling. Close liquid cooling had minor effect on the PUE-value. The traditional vapor compression cooling system is energy intensive, but it can be replaced, entirely or partly, by free cooling which utilizes coldness of outdoor air, water or ground. District cooling would decrease PUE-value and energy consumption of cooling, especially in summer, when air cooling based free cooling is not in use.