## 5 Conclusions  
Despite the evolution of data centers in reducing energy consumption, the index used to measure and compare energy efficiency between CRAC equipment does not yet use inverter technology resources (variable refrigerant flow) in its methodology. The IPLV for equipment already was developed for comfort air conditioning, but the Net Sensible COP methodology favors fixed-capacity equipment. The energy efficiency index needs to keep up with new technologies; according to [PERSON] et al. [18], the compressor frequency variation is one of the greatest technologies for reducing energy consumption in CRAC equipment. Both data center equipment and air conditioning systems are evolving. Another technology is microchannels coils with microfluids that can reduce heat dissipation from IT equipment \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **AHRI** & **COP1** & **COP2** & **COP3** & **COP4** \\ \hline Compressor freq. (Hz) & 73 & 64 & 67 & 69 & 73 \\ \hline Cooling capacity (kW) & 55 & 55 & 55 & 55 & 55 \\ \hline Evaporator capacity (kW) & 55 & 55 & 55 & 55 & 55 \\ \hline Condenser capacity (kW) & 67.5 & 64.1 & 65.6 & 66 & 67.5 \\ \hline COP/EER (kW/kW) & 4.43 & 5.98 & 5.46 & 4.97 & 4.43 \\ \hline Min. cooling capacity (kW) & 26.4 (35 Hz) & 329.6 (35 Hz) & 28.6 (35 Hz) & 27.7 (35 Hz) & 26.4 (35 Hz) \\ \hline Max. cooling capacity (kW) & 56.4 (75 Hz) & 63.5 (75 Hz) & 61.3 (75 Hz) & 59 (75 Hz) & 56.4 (75 Hz) \\ \hline Mass flow (kg/h) & 1240 & 1115 & 1159 & 1186 & 1240 \\ \hline Discharge gas temp. w/o cooling (\({}^{\circ}\)C) & 76.7 & 64.2 & 68 & 71.9 & 76.7 \\ \hline Result COP (kW/kW) & 4.03 & & & 4.92 & \\ \hline \hline \end{tabular}
\end{table} 
Table 10: AHRI vs. COP WEUED result comparison. with both air and water cooling [19]. However, microchannel coils can also be used in air conditioning equipment and improve energy savings [20]. The COP WEUED index measures more accurately the benefits of these new technologies. Just as the IPLV is an important milestone for air conditioning equipment, a COP WEUED index was created based on the 29 major cities in the world, which could be an important tool to compare CRAC equipment, gathering the best of the AHRI 1361, which prioritizes sensible heat, with the calculation of the EUED method and also with the IPLV formula. This methodology can be useful for further studies, as it can serve as a basis for manufacturing CRAC equipment with more connection to the real temperatures of the outside air, even recalculating the condenser fans, since the specific mass of the air is also related to temperatures. In addition to these advantages, the proposed method favors high-performance air conditioning equipment in the range in which they will be truly used, since technologies such as free cooling and evaporative cooling are already realities in data centers. Conceptualization, A.F.S. and P.D.G. ; methodology, A.F.S. ; validation, A.F.S. and H.J.L.d.S. ; formal analysis, A.F.S. and P.D.G. ; investigation, A.F.S. ; resources, H.J.L.d.S. ; data curation, A.F.S. and P.D.G. ; writing--original draft preparation, A.F.S. and H.J.L.d.S. ; writing--review and editing, P.D.G. ; visualization, H.J.L.d.S. ; supervision, P.D.G. ; project administration, A.F.S. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. Authors acknowledge Fundacao para a Ciencia e a Tecnologia (FCT--MCTES) for its financial support via the project UIDB/00151/2020 (C-MAST). The authors declare no conflict of interest. * _[PERSON] et al. (2017)_ _[PERSON]; [PERSON] A review of air conditioning energy performance in data centers._ Renew. Sustain. Energy Rev._ **2017**_, 67_, 625-640. [CrossRef]
* _[PERSON] et al. (2020)_ _[PERSON]; [PERSON]; [PERSON]. New Data Center Performance Index: Perfect Design Data Center--PDD._ Climate_ **2020**_, 8_, 110. [CrossRef]
* _NREL (2014)_ _NREL._ High-Performance Computing Data Center_; National Renewable Energy Laboratory (NREL), U.S. Department of Energy: Denver, CO, USA, 2014.