Data center waste heat recovery

Waste heat recovery means putting to use the heat a data center's servers reject, usually through a heat pump connected to a district heating network. In Stockholm, since 2017, the Stockholm Data Parks program has connected data centers to the Stockholm Exergi district heating network, which buys the heat rejected by the halls. Sweden did it on economics; Germany made it an obligation. The Energy Efficiency Act that took effect in November 2023 (EnEfG, Energieeffizienzgesetz) requires sites commissioned from July 2026 to reuse 10% of their energy, then 15% and 20% for those of the following two years. Article 26 of the 2023 EU directive points the same way above 1 MW. Heat from an air-cooled hall comes out around 30 °C, too low for a city network; a heat pump is needed, and direct liquid cooling, which returns warmer water, simplifies the job. For the insurer, the arrangement changes the site's profile. The operator signs a heat supply contract, with volumes, availability, sometimes penalties, and becomes a supplier a third party depends on. A cooling failure or a fire no longer cuts off only its IT customers: it deprives a heating network, a greenhouse or a swimming pool of a source. Most networks keep their boilers as backup, which limits the actual damage. The claim still lands on contractual ground, which many liability policies exclude when the commitment goes beyond what general law would have imposed. And the heat exchangers, pumps and water loops added right next to the halls come into the water damage analysis.