Worldwide energy analysis of major free cooling methods for data centers

Various free cooling methods are available for data centers that eliminate or reduce the need for mechanical cooling by utilizing outdoor air under certain conditions. It is evident that climate conditions affect the performance of free cooling modes. It also affects the performance of main components of the cooling infrastructure indirectly due to inefficiencies caused by the part load operation during free cooling modes. Hence, modeling key components of the cooling infrastructure is an essential element for reliable assessment of these methods. Most of the studies assessing energy saving potential of free cooling methods in the existing literature follow simpler approaches that do not consider the off-design performance of key cooling equipment. There are a few studies paying attention to these effects, but they address energy saving potential of only certain free cooling methods. This paper presents an overview of a comprehensive thermodynamic modeling study considering the off-design performance of major components of data center cooling infrastructure for an air cooled data center with 1 MW information technology (IT) load. Subsequent modeling effort integrates the most common free cooling methods; Direct Air-Side Economizer (ASE), Indirect Air-Side Economizer (IASE), Indirect Evaporative Cooling (IEC) and Indirect Water-Side Economizer (WSE); into the thermodynamic model of the data center. Based on hour-by-hour annual energy simulations in all climate zones defined by ASHRAE Standard 169-2013, the results provide a comparison of energy and water consumption of data centers utilizing various free cooling methods.