Dry cooling energy performance can rival evaporative cooling

PUE and WUE data from a sample of operating data centers across multiple ASHRAE climate zones and cooling system types are examined, including open evaporative cooling towers, dry coolers, air economizers, indirect and direct air cooling, adiabatic systems and hybrid coolers. The analysis challenges the widely held assumption that evaporative cooling represents the most efficient solution for data center cooling. The findings show that system design, configuration, free cooling utilization and operational discipline are stronger determinants of performance than system type alone, and that dry and adiabatic alternatives can match or outperform evaporative systems while consuming significantly less water.

KEY POINTS

• Evaporative cooling can achieve low PUE by consuming significant volumes of water, a trade-off that rarely features in the benchmarking data that shapes industry decision-making.
• PUE and WUE data vary widely within and across climate zones for all system types, driven by system design, configuration, free cooling capture, and operational discipline more than system category alone.
• Well-designed dry cooling and adiabatic systems can match evaporative cooling PUE across ASHRAE climate zones 2-6 with zero or near-zero water consumption.
• WUE should be treated as an equal metric alongside PUE in cooling system evaluation and benchmarking.