Cundall Engineering report: comparison of liquid and air cooling for datacenters

Key takeaways:

• Iceotope’s chassis‑level Precision Liquid Cooling© enables much higher rack densities, smaller data hall footprints, and simpler heat‑rejection facilities than advanced air‑cooled designs.
• Across multiple realistic data center scenarios, Iceotope liquid cooling cuts power and water use per kW of IT load (often by double‑digit percentages), lowers cooling and total operating costs per kW, and reduces CO₂ emissions while improving hardware reliability.
• Iceotope’s platforms offer plug‑and‑play, low‑dielectric‑volume alternatives to full immersion cooling, improving serviceability and deployment flexibility and making liquid‑cooled data centers quieter, more resilient, and less sensitive to poor air quality and humidity.

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This study by Cundall Engineering compares the effectiveness of liquid cooling and air cooling for data processing equipment, focusing on Iceotope’s chassis‑level precision immersion and direct‑to‑chip solutions across four realistic data center scenarios (hyperscale, colocation, edge, and tropical deployments). It explains key liquid‑cooling modalities (direct‑to‑chip, full immersion, chassis‑level precision immersion) and contrasts them with hybrid air‑cooled options such as in‑row and rear‑door units, noting that that air’s limited heat capacity constrains achievable rack power densities. The report situates liquid cooling within broader industry drivers: rising CPU and rack power densities, AI and other power‑hungry workloads, tightening environmental legislation, land constraints favoring higher‑density and multi‑storey facilities, and the increasing importance of waste‑heat recovery and reduced carbon and water footprints.

Other advantages of liquid cooling include support for much higher rack densities, potential data hall footprint reductions of around 86%, and reduced CAPEX due to less complex cooling infrastructure and smaller buildings.

Liquid systems benefit from water’s vastly higher volumetric heat capacity, higher supply temperatures that enable extensive free cooling, more effective waste‑heat recovery, sharply reduced or eliminated evaporative water use, and improved component reliability through uniform, hotspot‑free cooling. The report critiques standard efficiency metrics PUE and WUE for ignoring parasitic loads like fans and pumps, and proposes ITUE and TUE to capture server‑level and total efficiency, noting that server fans can consume ~10% of rack power versus ~3% for dielectric pumps, creating a “hidden” ~7% IT power saving with liquid cooling.

Through detailed energy and water modeling using ASHRAE weather data, Cundall quantifies the benefits of liquid cooling: water use per kW of ITE power falls up to 96%, power use per kW of ITE drops by around 40%, cooling cost per kW of ITE power falls by about 84%, and total cost per kW of ITE power decreases by approximately 40%. 

Liquid‑cooled designs also increase ITE capacity per hall by up to 55% and can cut the additional hall footprint by about 74% in high‑density scenarios. CO₂ emissions per kW of ITE power are reduced by about 39.5%, reflecting both lower total power demand and higher IT density. The Cundall report further notes that liquid‑cooled systems are quieter, less sensitive to poor air quality and humidity, and more resilient to brief power disruptions due to inherent thermal mass and the fast start‑up of dry/hybrid coolers. Overall, the study concludes that liquid cooling—particularly Iceotope’s chassis‑level Precision Liquid Cooling—can deliver substantial efficiency, sustainability, capacity, cost, and resilience advantages over best‑in‑class air‑cooled data center designs.

Read the executive summary or download the full report.