Land and data-center sites, North Carolina
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How does a data center work?

A data center works by running three paths at once. Power flows in from the grid to the servers. Heat flows out from the chips to the outdoors. Data flows in and out over fiber. Backup equipment keeps each path running when one part fails.

See if your land fits

Quick summary: This guide explains how a data center works through its three paths: power, heat, and data. It is for residents, landowners, and officials who want to know what the equipment on a site plan does. The key point: each path starts or ends outside the building, which is why a data center needs so much from its land.

How a data center works, in brief

A data center works by feeding power to computers, removing the heat they make, and connecting them to networks. The International Energy Agency defines it as a facility that houses servers, storage systems, and networking equipment in racks, plus the equipment that keeps them working.

The agency breaks down where the electricity goes:

Equipment What it does Share of electricity
Servers Process and store data About 60 percent on average
Storage systems Hold data and backups About 5 percent
Networking equipment Connects devices and directs traffic Up to 5 percent
Cooling Keeps equipment within its temperature range About 7 percent to over 30 percent

The shares vary by facility type. Cooling takes about 7 percent in efficient hyperscale facilities and over 30 percent in less efficient enterprise facilities.

The power path: from the grid to the rack

Power reaches the servers through a chain of equipment that steps the voltage down and protects it from interruption. Large data centers often have power lines and substations that connect them directly to nearby high-voltage transmission lines, according to Virginia’s legislative audit commission.

The Department of Energy’s design guide describes the typical path inside the fence:

  1. Utility service. The utility delivers power, usually at a medium voltage of around 12 kilovolts or more.
  2. Switchboard and switchgear. This equipment distributes the incoming power inside the facility.
  3. Backup generator. A generator stands in as the alternate source during a longer outage.
  4. Uninterruptible power supply. Battery banks or other systems carry the load through short gaps.
  5. Power distribution units. These carry conditioned power to the rows, often stepping 480 or 208 volts down to 120 volts.
  6. Server power supplies. Each server converts the alternating current it receives to the direct current its parts use.

Each step loses a little energy as heat. That heat joins the heat from the servers.

Backup power and redundancy

Backup power keeps the servers running when the grid fails. The International Energy Agency describes batteries and backup generators as rarely used but necessary for the reliability data centers must meet. The Virginia study states that all data centers have backup generators on site.

Designers also duplicate equipment. The Department of Energy guide describes paired uninterruptible power supply units sized so that one can fail without loss of service. North Carolina’s state technology agency describes its own colocation service as having redundant power feeds, backup generator power, and conditioned power supported by uninterruptible power supplies. Data center redundancy: what it means and what it asks of land explains the N+1 and 2N terms.

The heat path: from the chips to the outdoors

The servers turn electricity into heat, and the cooling system carries that heat outdoors in stages. A federal energy program page notes that the equipment runs 24 hours a day and needs cooling without a break. It traces one common design:

  1. The servers draw cool air in at the front and blow warm air out the back.
  2. Computer room air-conditioning units pull the warm air from the room and pass its heat to a chilled water loop.
  3. A chiller moves the heat from the chilled water loop to a condenser water loop.
  4. The condenser water carries the heat to a cooling tower, which evaporates water to release the heat to the air.

The Department of Energy guide describes the layout that makes step one work. Racks stand in rows, with cold aisles in front and hot aisles behind, so hot exhaust does not mix with cool supply air.

Other designs change the later steps. Free cooling uses cool outdoor air, or a cooling tower alone, to cool the building without running the chillers in mild weather. Dry coolers release heat to the air without evaporating water. Direct liquid cooling brings fluid to the chips through cold plates, or submerges the servers in a fluid that does not conduct electricity. The heat still has to leave the site through outdoor equipment. Data center cooling systems and what they ask of a site compares the designs.

The short version: Power comes in, heat goes out, and data moves both ways. The substation, the generators, the cooling yard, and the fiber entrances are where those paths cross the property line.

The data path: from fiber to the servers

Data reaches the servers over fiber-optic cables that enter the building and connect to network equipment inside. The International Energy Agency lists that equipment: switches connect devices within the data center, routers direct traffic, and load balancers spread requests across servers.

Inside, switches link each rack to the rest of the building. Servers process requests, and storage systems hold the data. The national laboratory report for the Department of Energy tracks the switch ports in United States data centers. It found that ports faster than 50 gigabits per second made up 64 percent of the installed base around 2023.

Outside, fiber should enter by more than one route, so that one cut cable does not isolate the building. Two providers can still share one trench. Fiber route diversity: why two carriers are not two routes explains why.

How efficiency is measured

Efficiency is measured mostly by power usage effectiveness, the ratio of the facility’s total energy to the energy its computing equipment uses. The Department of Energy guide reports an average of 1.6 and notes that some very efficient facilities reach below 1.1. A lower number means less energy goes to cooling, power losses, and lighting. What is PUE (power usage effectiveness)? explains the ratio.

Take action: If you own land near transmission lines and fiber, the record can show whether the three paths could reach it. Start with Is your land a data-center site?

What the three paths ask of a site

Each path needs something from the land. The power path needs a utility that can serve the load and room for a substation and a generator yard. The heat path needs water and sewer service for evaporative designs, or yard space for dry coolers and chillers. The data path needs fiber that can reach the site by separate routes.

The building cannot supply any of these by itself. Data center power requirements: what a campus needs from the grid covers the largest of them.

What the public record shows

The public record shows nearby transmission lines, substations, water and sewer service areas, and some fiber routes. It cannot show whether the utility has capacity for the load, how much water a design will use, or whether two fiber routes are truly separate. The serving utility, the water provider, and the fiber carriers confirm those. The equipment you will see outside is described in What does a data center look like?, and the wider objections are checked in Are data centers bad? The objections, checked against the record.

Key recap

  • A data center runs three paths: power in from the grid, heat out to the air, and data in and out over fiber.
  • Power steps down from utility voltage through switchgear, an uninterruptible power supply, and distribution units to the racks.
  • Batteries bridge short gaps, generators cover longer outages, and duplicate equipment covers a failed part.
  • Heat moves from the chips to room air or liquid, then to chillers, cooling towers, or dry coolers outdoors.
  • Each path crosses the property line, so the site must supply power, water or yard space, and fiber.

Questions

Do data centers run all the time?

Yes. The servers run around the clock, so the power and cooling systems run continuously too. Backup equipment exists so that a failure or an outage does not stop them.

Why do data centers need so much cooling?

The servers turn the electricity they use into heat. If the heat stays in the room, the equipment overheats. Cooling takes about 7 percent to over 30 percent of a facility’s electricity, depending on the type.

What happens to a data center when the power goes out?

Batteries in the uninterruptible power supply carry the load for the first moments. Backup generators start and carry it until the grid returns.

References

Primary sources cited on this page, in APA style.

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