By Eamonn Ryan
Cape Town’s emergence as a major data-centre location is bringing a familiar infrastructure question into sharper focus: where does all the heat go? This is part one of a three-part series.
The challenge is becoming more significant as AI and high-performance computing increase rack densities. DC Studio | Magnific.com
The question has become particularly relevant following the decision by Cape Town’s Municipal Planning Tribunal to approve Equinix’s proposal for two data centres in the King Air Industria area. The proposed facilities are expected to require around 170MW of power capacity, making the development one of the largest proposed data centre projects in South Africa. Equinix has confirmed that it owns the land but has not yet submitted a site development plan.
The decision attracted objections relating to the development’s environmental footprint, including electricity and water requirements. But from an HVAC&R perspective, the more interesting question is how that electricity demand translates into a cooling requirement.
Almost all the electrical energy consumed by IT equipment ultimately becomes heat. That heat must be continuously removed to maintain the temperature and environmental conditions required for reliable operation.
Equinix has indicated that its proposed Cape Town facilities would use dry, air-based cooling, meaning that water would not be required for data hall cooling. This is an important distinction in a water-constrained city.
Dry cooling, however, is not simply a question of eliminating water consumption. The designer must balance water use against electrical efficiency, ambient conditions, equipment density, reliability and capital cost.
Power Usage Effectiveness (PUE) provides one way of looking at the issue. It compares total data centre energy consumption with the energy consumed by IT equipment. The lower the PUE, the less additional energy is being used to support the computing load.
Cooling therefore becomes an important part of the efficiency equation. Air management, higher allowable supply-air temperatures, economisation and efficient heat-rejection systems can all reduce mechanical cooling demand. ASHRAE’s latest guidance for AI data centres specifically highlights airflow optimisation, economisation and low- or no-water cooling as important strategies.
The challenge is becoming more significant as AI and high-performance computing increase rack densities. Conventional air cooling remains highly relevant, but high-density applications are increasingly driving interest in direct-to-chip and other liquid-cooling technologies.
For Cape Town, therefore, the question is not simply whether 170MW of data centre capacity represents a large electricity demand. It is also about how efficiently that energy can be converted into computing capacity, how the resulting heat is rejected, and what resources are consumed in the process.
That raises a broader question for the city’s future data centre development: if waterless air cooling is one solution, are there other heat sinks that could potentially be used?
Cape Town has one particularly obvious resource on its doorstep: the Atlantic Ocean.
Read next: Could the ocean help cool Cape Town’s data centres?
