Circular DatacenterDesign,Build,Reuse.

Where energy enters the site, at the interface with the public grid. It caps the available capacity: on a retrofit, what it can carry decides what the building can host.

Medium-voltage switchgear distributes and protects; transformers step the voltage down to usable low voltage. These are very long-life assets, where reuse saves several quarters of lead time.

The main low-voltage switchboard distributes power to the halls and the utilities. This is where discrimination is decided: a fault must be cleared as close as possible without tripping anything upstream.

The uninterruptible supply holds the load until the backup starts. We requalify UPS units but always replace batteries with new: their ageing cannot be recovered.

The last line of backup, with its fuel tanks and bunding. A generator only counts once its load acceptance has been tested for real, several times - untested redundancy is a hypothesis.

Chillers and free cooling, producing the chilled water. In the French climate a large share of the year can be covered without compression - provided the loop accepts warm enough water.

The networks carrying cooling to the halls, and the units that deliver it. This is the package most deeply transformed by the arrival of direct liquid cooling.

The usable space: rack layout, aisle containment, cable routes and raised floors. At AI densities, room geometry matters as much as installed cooling capacity.

Physical security zones, access control, video surveillance and very early smoke detection. These are drawing-board decisions: added later, they force partition rework.

The building management system, which makes everything else visible and controllable. Without measurement points designed in from the start, neither energy reporting nor certification is possible.