## 10 Conclusions  
This paper provided a detailed framework for the energy exploitation of the low-grade waste heat of data centers, considering their typical operating conditions and energy streams, adopting ORC systems for electrical energy to promote an efficient transition towards a more sustainable future. Estimates suggest that power consumption in data centers ranges from 15 to 20 kW/m\({}^{2}\), potentially reaching as high as 96 kW/m\({}^{2}\) in specific instances. The resulting thermal output is considerable, as electronics tend to heat up, making cooling an essential aspect of their operation. The literature suggests that about 50% of the heat from cooling electronic equipment can be exploited (and, in some cases, more than 70%). The discussion covered various cooling strategies, including air, liquid, and two-phase fluid-based systems, and their efficiency in thermal waste management. Air cooling systems, favored for their related simplicity, represent approximately 70% of the cooling methods employed. Water cooling has demonstrated greater effectiveness, enabling significant reductions in cooling flow rates, albeit less commonly adopted compared to air cooling solutions. The waste heat  
Figure 7: Heat exchange from the heat source to the ORC system. from data centers typically manifests as warm air or hot liquid water. Concerning air-based cooling, roughly 80% of the heat is at temperatures around 30 \({}^{\circ}\)C, related to overall air flow, including within rooms, while the rest ranges from 50 to 60 \({}^{\circ}\)C, stemming from the cooling of high-heat equipment. A corresponding temperature within a 50-80 \({}^{\circ}\)C range is typical for liquid water. The investigation thus supported the adoption of ORC technology as a viable method for generating electricity from low-grade heat. The findings indicated that electric efficiencies higher than 5% are attainable in data centers by employing ORC systems with low-boiling fluids. A crucial focus of this study was the analysis and selection of working fluids, highlighting that there is no universally optimal fluid for any specific temperature range or application due to the potentially vast array of fluids and the varying criteria for selection. The key challenges encountered depend on the maximum and minimum operating pressures. These concerns are related to (1) the capability to vaporize the fluid using the available thermal source temperatures and (2) the capacity to achieve condensation with naturally available resources, such as ambient water. This paper proposed a standardized structure for an energy system, outlining the components and their functions. For this purpose, an organic Rankine cycle was analyzed, including fluid streams for internal operations. The design and sizing criteria were detailed, starting from the thermodynamic analysis to continuing with the energy performance investigation of the entire system. An application case completed this study using the DWSIM computational environment. Warm air and hot liquid water were considered for the primary heat source at the potential temperatures of 50-60 \({}^{\circ}\)C and 50-80 \({}^{\circ}\)C, respectively. A secondary air mass flow at 30 \({}^{\circ}\)C complemented the pre-heating section. The condensation process utilized underground water at a temperature equal to 10 \({}^{\circ}\)C. Given the specific temperature requirements for evaporation and condensation to match the thermal and cold-water resources, respectively, pentane and isopentane were identified as suitable working fluids. For the pentane ORC system, operating pressure ratios of 2.6 and 6.4 led to net electric efficiencies of 3.4% and 7.1% at the plant level, respectively. Meanwhile, the isopentane system achieved net electric efficiencies ranging from 3.6% to 7.0% at operating pressure ratios from 2.7 to 6.0. The most favorable results were obtained when utilizing liquid water as the heat source.