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The language of African data centres – 15 terms every infrastructure professional should know

Ask a hyperscaler procurement team what matters most in a Request For Information (RFI) and they’re start talking about PUE (which in this case does not mean productive use of energy). 

If you ask a facilities engineer running a water-cooled chiller the same question, they’ll start talking about cost and not efficiency being what drives the conversation. 

The vocabulary of data centre cooling is expanding quickly because the infrastructure is evolving so fast. The concepts of closed-loop systems, rear-door heat exchange or water usage effectiveness metrics didn’t even exist in mainstream conversations ten years ago. 

And now that’s all being reshaped again by AI-driven rack densities. 

Here’s the start of a working glossary in progress for a sector whose terminology is being written in real time. This was compiled after the Water Security Africa panel discussion on water usage at African data centres.

 

Adiabatic cooling

 An evaporative wet-cooling method for data centres.

Effective in some climates, but unsuitable in high-humidity environments such as Nigeria. 

Chilled water system

A wet-cooling method used in data centres, circulating treated water through chillers to remove heat from the facility. 

Closed-loop cooling

A data centre cooling method that circulates a fixed volume of water continuously, limiting consumption to leaks or scheduled treatment.

Widely regarded as the most viable option for water-constrained African markets. 

Colocation

A data centre model where an enterprise client houses its equipment in a shared facility rather than building and operating its own, with the operator managing power, cooling and security. 

Data sovereignty

The requirement, increasingly enforced by African governments, that data generated within a country be stored and processed within that country, driving hyperscalers to colocate locally. 

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Direct expansion (DX) cooling

A refrigerant-based, air-cooled data centre cooling method requiring no water input.

Common in African markets facing water infrastructure constraints. 

Free cooling

A cooling method using outside ambient air instead of mechanical systems.

Seasonally available in some South African regions, such as Johannesburg in winter. 

Hyperscaler

A very large-scale cloud or data centre operator (eg Google, Meta, AWS) whose facilities require significant power and cooling capacity. 

N+1 (concurrently maintainable)

A data centre redundancy standard where at least one additional unit of capacity (beyond what’s needed) is available, allowing maintenance without downtime. 

PUE (Power Usage Effectiveness)

The standard data centre efficiency metric: total facility energy divided by IT equipment energy.

A lower figure (closer to 1.0) indicates greater efficiency. Widely used because it’s directly billable. 

Rear door heat exchange

A closed-loop cooling method where heat is extracted from server racks at the rear, enabling higher-density scaling without raised flooring or containment. 

RFI (Request for Information)

An early-stage procurement document in which a buyer (eg a hyperscaler) asks vendors to share capabilities before a formal bid process. 

RFP (Request for Proposal)

A formal procurement stage in which vendors submit priced, detailed solutions against a buyer’s defined requirements. 

Tier III (data centre)

A data centre design standard requiring concurrent maintainability, meaning any component can be taken offline for maintenance without disrupting operations. 

WUE (Water Usage Effectiveness)

A data centre metric measuring litres of water consumed per kilowatt-hour of IT load: the water-equivalent of PUE.

Currently averages around 1.8 litres per kilowatt-hour across Africa.

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