Comparison of the energy efficiency of a water-sideeconomizer (WSE) with that of ASE in temperate or semi-tropicalregions, done by Cho et al. [25], showed an improvement of 16.6% and42.4% in energy efficiency, annually. Ham et al. [26] proposed a favorable supply air temperature range from 18 °C to 23 °C based onenergy optimization of an ASE in a modular data center, consideringdifferent parameters. In another work, Ham et al. [27] figured out thatdifferent ASEs can lead to cooling load savings of 76–99% in comparison to mechanical cooling systems in data centers. Accordingly, theyconcluded that the total energy savings of the economizers varies from47.5% to 67.2%. Deymi-Dashtebayaz and Valipour [28] investigated athermo-economic analysis for using ASE, WSE and combined air orwater economizer (CAWE) operation mode in order to cool down a datacenter in ten cities of Iran with various weather conditions. Based ontheir result, the economic index of relative net present value (RNPV) forASE, WSE and CAWE will be positive if their relative annual potential(RAP) are higher than 12%, 23% and 35%, respectively.Because of their servers and a large number of electric components,data centers produce a considerable amount of heat which is usuallywasted. While this generated heat can be used as a heating source forthe office buildings often exist close to the data centers. Besides theeconomic and environmental benefits of the waste heat recovery fromdata centers, the energy performance index of the data centers can alsobe improved [29]. Reusing the waste heat of the data centers have beenstudied by several researchers. Zhang et al. [30] suggested a watercooled integrated air conditioner with thermosyphon as a heat recoverysystem for cooling the internet data centers and heating the officebuilding near the data center. They found that, using the proposedsystem, there are 33% and 60% cooling and heating energy savingpotential respectively, compared to cooling and heating systems. Thefeasibility of pre-heating the water supply of a power plant throughreusing the waste heat of the data centers was investigated by Marcinichen et al. [31]. Their results of reusing the data centers waste heatindicated an improvement of 2.2% in power plant efficiency which canlead to CO2emission and fuel consumption reduction. Lu et al.