# Heat reuse & district heating interfaces

Part ID: 6.07 · Layer 6 (Facility cooling & HVAC)

Heat exchangers and interconnection equipment that export waste heat from a data center's cooling loop into a district heating network or other end use instead of rejecting it to atmosphere.

Taps the facility water loop (6.05) — typically its warmer, IT-heat-carrying side — and routes it through a heat exchanger, and where the reuse temperature needs boosting, a large heat pump, into a district heating network or process-heat customer, displacing some of the heat-rejection equipment (6.02) a site would otherwise need. Adoption is concentrated where district heating networks already exist and local economics or regulation favor it, so it remains a minority design choice rather than a default. Higher-temperature liquid-cooling loops in AI racks produce warmer reject water than legacy air-cooled facilities, which is exactly the direction that makes heat reuse more thermodynamically attractive, since a heat pump has less work to do raising an already-warm source to district-heating temperature. Investors should treat this as a niche but growing interconnection market tied to specific geographies with district heating infrastructure, not a broad-based demand driver across the layer.

**AI delta:** Liquid-cooled AI racks run their facility loop hotter than legacy air-cooled halls, producing waste heat closer to the temperature district heating networks need and lowering the heat-pump work required to reuse it.

## Companies

| Company | Role | Confidence | Ownership | Ticker | Note |
|---|---|---|---|---|---|
| Alfa Laval | manufacturer | inferred | public | ALFA.ST |  |
| Carrier | manufacturer | inferred | public | CARR |  |
| Fortum | manufacturer | inferred | public | FORTUM.HE |  |
| MAN Energy Solutions | manufacturer | inferred | subsidiary |  |  |
| Siemens Energy | manufacturer | inferred | public | ENR.DE | large heat pumps |
| Trane | manufacturer | inferred | public | TT |  |
| Danfoss | manufacturer | inferred | private |  |  |
| Kelvion | manufacturer | inferred | private |  |  |
| Qarnot | manufacturer | inferred | private |  |  |
| Vattenfall | manufacturer | inferred | state |  |  |

Confidence tags: disclosed = company/filing statement; reported = trade press or partner list; inferred = taxonomy lead.