By Eamonn Ryan
This article is derived from a presentation delivered by Michael Young, Application Engineer – Thermal Management at Vertiv and a regular contributor to RACA Journal, at FRIGAIR 2025. This is Part 2 of a two-part series.
With an existing data centre, low density server racks may still employ the use of air-cooled cooling units. Rawpixel/Freepik
Young’s insights, shared on the topic of ‘Design of data centres for optimal energy efficiency’, explore the impact of artificial intelligence on data centre operations and the evolving strategies for effective thermal management.
A typical liquid cooling system comprises two main loops:
- Technology loop: This loop directly cools the IT servers. Hot fluid from the servers flows into a Cooling Displacement Unit (CDU), where it exchanges heat with colder water from the facility loop via a plate heat exchanger.
- Facilities loop: This loop supplies chilled water to the CDU and is responsible for ultimately rejecting the heat to the outside environment, often through chillers or dry coolers.
Effective liquid cooling requires sophisticated control. Sensors monitor the supply water temperature to the racks, adjusting a three-way valve to regulate water flow back to the chiller. A pressure transducer then senses changes in water flow rate and adjusts the speed of variable-speed pumps. This dynamic control ensures optimal cooling precisely when and where it’s needed, adapting to varying computational demands (e.g., peak loads during events like Black Friday).
Data centre downtime is incredibly costly and to mitigate this risk, redundancy is a non-negotiable principle in data centre design. This means implementing N+1 redundancy, where if two pumps are required for operation, a third is provided as a backup. Similarly, if 600 kW of cooling capacity are needed, two 600 kW cooling units might be installed to ensure continuous operation even if one fails. Each cooling unit within the system typically contains multiple pumps, a plate heat exchanger, expansion tanks, and comprehensive monitoring sensors and valves.
What could the data centres of the future look like?
Data Centres that implement AI can have two types of construction, namely an existing data centre that implements AI and a new data centre.
With an existing data centre, low density server racks may still employ the use of air-cooled cooling units that operate on relatively lower water temperatures which may be in the region of 20°C to 30°C. To utilise the principle of free cooling, a separate water loop may be implemented to provide cooling for the AI servers whereby the water in this loop is at a higher temperature. Therefore, within this arrangement, we may possibly see data centres that contain two separate water loops, one for the low-density servers and one for AI servers.
This drive for high-temperature water management is a significant industry trend because it dramatically enhances the potential for free cooling. If a data centre’s AI cooling loop runs at 43°C, it will almost always operate in free cooling mode in climates like Johannesburg, where ambient temperatures rarely reach such high extremes.
In essence, the data centre of the future will be characterised by sophisticated thermal management, hybrid cooling approaches, and a relentless focus on energy efficiency driven by the ever-increasing demands of AI and advanced computing.
