Sub-system
Most computing capacity in existence is still air-cooled, and for most workloads it remains the right answer. The design discipline is simple to state and hard to execute: never let hot air and cold air mix, and use outside air whenever the climate allows.
In one sentence
Air cooling removes heat by moving conditioned air through equipment, using physical containment to keep supply and return air separated and economisers to use outside air when conditions permit.
The single largest improvement in air cooling was containment. In an uncontained hall, hot exhaust mixes with cold supply, so the supply must be made colder than necessary to compensate — which wastes energy at the chiller. Physically separating the aisles allows the supply temperature to rise substantially, and warmer supply air is much cheaper to produce.
The second was raising the acceptable operating temperature. Equipment specifications permit far warmer inlet air than operators traditionally used. Running warmer allows more hours of the year to be served by outside air alone, which in a suitable climate removes mechanical cooling for most of the year.
Removing heat with air requires a volume of airflow proportional to the heat and inversely proportional to the acceptable temperature rise. As rack power climbs, the required airflow climbs with it — until the fan power needed is a significant fraction of the load, the air velocity becomes disruptive, and the temperature rise across the rack is uncontrollable. That is the wall, and it sits around thirty to forty kilowatts a rack.
When outside air is cool enough, heat can be rejected without running compressors — either by bringing filtered outside air in, or by using it to cool a water loop. Since compressors are the largest single consumer in a mechanical plant, the number of hours a year a site can economise is one of the main reasons climate influences site selection.
Most new facilities are not exclusively one thing. Liquid-cooled racks still need air for their power supplies, network equipment and drives, and a hall commonly hosts both liquid-cooled AI racks and air-cooled general infrastructure. Designs therefore have to support both, which complicates the plant.
Technology dependencies are solved by engineering; supply dependencies are solved by building something, which takes years.
Large air handlers and chillers are long-lead capital equipment in their own right.
Chillers and air handlersHow warm a hall may run is set by equipment specifications and industry guidance, and running warmer is what enables economisation.
An air-cooled hall needs colder water than a liquid-cooled one, which usually means evaporation or mechanical refrigeration rather than dry coolers alone.
Heat rejection and waterPhase-down schedules for high-global-warming refrigerants decide which chillers can still be bought, and a plant specified around a fluid being withdrawn has to be redesigned.
Other pages in this map that name Air cooling as something they cannot do without.
What each company supplies at this step, and — where a public figure exists — its share of this specific market — with what that share measures, the period it covers and who published it. Some rows also show the company’s own reported revenue for the segment covering this step, which is a different thing: it says how much this business matters to that company, not how much of the market it holds. Not a ranking and not a recommendation.
Supplies air handling, containment and thermal management systems.
Supplies chillers, air handling and building controls.
Supplies chillers and cooling systems for large facilities.
Supplies cooling equipment for commercial and data-centre applications.
Supplies room and row cooling alongside the electrical infrastructure it is sold with.
Supplies evaporative and adiabatic units for the sites that cool with air and water rather than mechanical plant.
Supplies precision air handlers, and is one of the few remaining independents in that equipment class.
The largest air-conditioning manufacturer, supplying the chillers and handlers underneath many branded systems.
Whether general-purpose computing density rises enough to push it past air's practical limit.
Whether higher permitted operating temperatures widen the geography where economisation works.
How hybrid halls are designed as the liquid share of the fleet grows.
Each page explains one technology in plain language, states what it depends on, and names companies by what they supply at that step. Company roles are described qualitatively and deliberately carry no market shares, revenue figures or rankings — those change faster than an explainer can, and a stale number is worse than none. Ticker links point at company pages on this site and are provided for reference only.
Nothing here is investment advice, a recommendation, or a forecast. A company named on a page about a technology is not thereby a good investment, and the chokepoints described are structural facts about supply chains rather than predictions about prices. Technology moves; where a page describes something as unresolved or in development, that was true when it was written.
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