Copenhagen’s 22.5 MW atNorth Data Center Pipes Waste Heat to 8

A 22.5 MW data center in Ballerup, Greater Copenhagen is now operational with a power usage effectiveness rating below 1.2, nearly half the industry average of 1.5 to 1.8 for air-cooled facilities. atNorth’s DEN01 facility uses direct liquid cooling to generate warm water as a byproduct, which supplies heat to more than 8,000 homes via Vestforbraending’s district heating network starting in 2028.

How Waste Heat Recovery Works at Scale

Cooling accounts for 30 to 40 percent of total data center electricity consumption. At DEN01, direct liquid cooling replaces air handlers with water flowing directly through server components, producing warm water at roughly 38 degrees Celsius as exhaust. District heating systems in Denmark require water at approximately 66 degrees Celsius. Heat pumps bridge this temperature gap before the heat enters Vestforbraending’s network. The arrangement converts previously wasted electricity into a monetizable thermal commodity that offsets natural gas consumption in residential heating. A facility running at PUE 1.5 spends 50 watts on overhead for every 100 watts delivered to IT equipment. At PUE 1.2, that overhead drops to 20 watts, translating to roughly $2.4 million in annual electricity cost savings for a 22.5 MW facility.

The Pipeline and Implementation Lessons

atNorth’s broader project pipeline shows where this technology is heading. The company’s planned Sweden campus spans 200 to 500 MW. DEN02 channels waste heat into vegetable cultivation through a partnership with Wa3rm, and FIN02 heats a Kesko retail store in Finland. The repeating constraint is geography: district heating networks exist primarily in Scandinavia, Germany, and Eastern Europe. A data center in suburban Virginia or Phoenix generates the same thermal byproduct with nowhere to send it. The Copenhagen model works because Vestforbraending’s infrastructure already reaches residential neighborhoods within pipe distance of the facility. For facility managers evaluating cooling investments, DEN01 establishes a concrete reference point: direct liquid cooling achieves sub-1.2 PUE at commercial scale, and when paired with regional heat off-take agreements, it produces measurable secondary revenue.

Critical Analysis

The 22.5 MW DEN01 facility GPU/HPC server PSUs operate as switch-mode rectifiers injecting 5th and 7th order harmonic currents; at rack densities of 40-100 kW, measured THDI reaches 10-15%, generating K = sum(h2*Ih2) values of 4-8 which trigger IEEE C57.110-2018 transformer derating to 0.75-0.85 of nameplate. A 22.5 MW single-campus load represents a significant demand concentration on the Ballerup 10 kV feed; however, PUE 1.19 versus the 1.5-1.8 industry average saves approximately 6-13 MW of cooling-related load, reducing reactive power burden from CRAC/CRAH VFDs.

5-Year Projection

By 2031, operational data from facilities like this will become the standard requirement for securing interconnection agreements, as ISOs prioritize proven Direct Liquid Cooling profiles.

Critical Perspective

The atNorth 22.5 MW data centre heat reuse project delivers thermal energy to approximately 8,000 Copenhagen homes — an impressive deployment of waste heat recovery, but one that depends on continuous data centre operation at high utilisation rates: district heat supply from a single facility represents a grid vulnerability if the data centre experiences an outage during a period of peak heating demand. Waste heat recovery projects of this type in Scandinavia — including Fortum’s Helsinki data centre heat network and Stockholm Data Parks — have consistently found that actual heat delivery runs 10–20% below nominal data centre power consumption due to seasonal IT load variation and cooling system efficiency losses. At 22.5 MW and 8,000 homes, the implied average heat load per household is approximately 24.6 MWh/year — plausible for Danish climate, but achievable only if 100% of facility waste heat is recoverable, which liquid cooling systems achieve only in the most favourable configurations. The question district heat planners should be asking: what backup heat source is contracted to cover periods when the data centre is unavailable, and at what additional cost per MWh does the district network remain solvent?

Related Coverage

• Liquid Cooling Cuts Data Center Power Use by 10%: liquid cooling reduces data center power use
• Data Center Chiller Retrofit Cuts PUE from 1.42 to 1.30: data center chiller retrofit cuts PUE
• CenterPoint Logs 700% Surge in Data Center Grid Requests as U.S. Queue Hits 1,400 GW: data center grid requests surge
• Data Center Grid Interconnection Now Takes Up to a Decade: data center grid interconnection takes decade