Energy saving strategies in green data center designing based on aerosol corrosion prevention

Data centers (DC) are responsible for a large global electricity usage mainly due to their cooling systems. Air conditioning (AC) costs could be reduced using a Direct Free Cooling (DFC) system which uses outside air to directly cool the information technology (IT). However this approach involves the risk to introduce outdoor aerosol which can become electrically conductive if the surrounding air reaches the aerosol Deliquescence Relative Humidity (DRH), thus damaging electronic equipment. In this work we present a study aimed to increase DC energy efficiency, whilst at the same time preventing aerosol corrosion. The study was conducted in Italy at Sannazzaro de' Burgondi (SdB, Po Valley), to specifically optimize the operating conditions of a DC designed for the Italian National Hydrocarbon Institution (ENI) (5,200 m2 of IT installed, 30 MW). Aerosol number size distribution was monitored and allowed to estimate the aerosol level entering the DC; moreover aerosol chemical composition was investigated and allowed to estimate the aerosol free acidity and the aerosol DRH using the thermodynamic Aerosol Inorganic Model (E-AIM). E-AIM output were validated through laboratory tests, using an Aerosol Exposure Chamber, and through a comparison among "wet" and "dry" aerosol size distribution measured at SdB. From these data it was possible to design the filtering system of the DC and to estimate the outdoor air supply time, by DFC, and thus to estimate the energy consumption of the DC. A potential energy savings of 60% was estimated compared to a traditional AC cooling system with a potential energy saving of 7358 kWh and 2.67 t of CO2 (for 1 kW of installed IT)