Free Cooling for Saving Energy: Technical Market Analysis of Dry, Wet, and Hybrid Cooling Based on Manufacturer Data

Abstract

In light of energy and climate targets, free cooling unlocks a major resource-saving potential compared to refrigeration. To fill the knowledge gap in quantifying this saving potential, we aim to specify the physical and technical limits of cooling tower applications and provide comprehensive data on electricity and water consumption. For this purpose, we distinguish six types of package-type cooling towers: dry, closed wet, open wet, and three types of hybrid systems; defining one generalized system for all types enables comparability. Subsequently, we collect data from 6730 system models of 27 manufacturers, using technical information from data sheets and additional material. The analysis reveals, for example, specific ranges of electricity demand from 0.01 to 0.06 kWel/kWth and highlights influencing factors, including type and operating point. Refrigeration systems would consume approximately ten times more electricity per cooling capacity. Furthermore, the evaluation demonstrates the functional limits, for example, the minimum cooling temperatures. Minimum outlet temperatures using evaporative cooling are up to 16 K lower than for dry cooling. The collected data have crucial implications for designing and optimizing cooling systems, including potential analysis of free cooling and efficiency assessment of cooling towers in operation.

Catalyzing Cooling Tower Efficiency: A Novel Energy Performance Indicator and Functional Unit including Climate and Cooling Demand Normalization

“…Building upon the concept of the EER and specific electricity consumption, we implement the thermodynamic ideal as the efficiency reference point, allowing for targeted comparability between different cooling tower processes. For validation, we apply the novel indicator to a comprehensive dataset, including 6575 cooling tower models by Wenzel et al [39]. Moreover, as a case study, we evaluate the efficiency of a data center's wet cooling system by analyzing the logged data for 2019.…”

“…Cooling towers have different designs to serve diverse requirements across sectors. We classify the following six types of cooling towers in line with Wenzel et al [39] (cf. Table A1 in the Annex for the detailed definitions):…”

“…Firstly, we use the AirPI to assess the cooling towers in the dataset by Wenzel et al [39] to cover a broad range of different cooling tower models. The data include the six types of cooling towers described in Section 2.2.…”

“…Differences between both indicators generally result from including the ambient and cooling temperatures in the calculation of the AirPI. Furthermore, the higher scattering of dry cooling may result from a higher scattering of the ambient temperature of operating points in the dataset compared to wet and hybrid cooling [39] (p. 8).…”

“…All three have one physically ideal case (highlighted in green). In practice, technical imperfections cause additional effort or losses (in gray), resulting in the actual situation (in blue).The efficiency values of the ventilation, motor, fan, or flat belt and control system are approximate benchmarks by literature[47,48] (pp [35][36][37][38][39][40][41][42],. [49] (pp.…”