Material Insights · Understanding the Material World

Shared and district heat reuse: Engineering and integration

Matching year-round heat with seasonal demand

What this tab covers Engineering and operating integration: how tightly it is coupled to the host process, how steady the waste stream is, and how hard it is to retrofit.

Source and network run on different priorities, so each side keeps its own backup; the main engineering challenge is matching year-round heat with seasonal demand.

Process interdependence (coupling risk)

Mixed

A data centre cannot let servers overheat because the heat network is full, so it keeps its own coolers; the network keeps peak boilers in case the source stops. In Stockholm the utility pays only for heat actually delivered, which keeps the coupling commercial rather than technical. Kalundborg is more tightly linked: 17 public and private companies swap more than 20 streams of water, energy and materials, so one partner's closure affects others.615

Kalundborg partners 17 public and private companies15

Load factor and intermittency

Favourable

Data centres and sewage run all year but heat demand falls in summer, which limits hours unless cooling is also sold. Katri Vala produces over 1,000 GWh a year from 160 MW, about 6,250 full-load hours (calculated), well above the 3,000 to 4,000 hour target, helped by selling cooling in summer. Odense's design of 100,000 MWh from up to 25 MW implies about 4,000 hours (calculated).5912

Katri Vala full-load hours about 6,250 h/yr (calculated)9 Odense full-load hours about 4,000 h/yr (calculated)5 Helen Eiranranta (opened August 2026) about 90 MW heat, about 300 GWh/yr12

Footprint and retrofit complexity

Mixed

Schemes need a heat network close by, which is why they cluster in Nordic cities. The Fortum scheme feeds a network of about 900 km of underground pipes and, besides its heat pumps, needed 200 MW of electric boilers and an 800 MWh hot-water store. Katri Vala sits underground beneath a city park, showing that large urban heat pumps can be hidden; Bunhill 2 in London fits a 1 MW heat pump at a tube ventilation shaft. India has almost no district heating, so the nearer Indian analogue is district cooling or hot water for hotels and hospitals.781014

Fortum network length about 900 km7 Bunhill 2 heat pump 1 MW10 Fortum backup and storage 200 MW electric boilers; 800 MWh thermal store14

Sources

  1. Odense Data Center 2 Meta (Facebook Engineering), 2020
  2. Stockholm, Sweden: heat recovery from data centres (Covenant of Mayors case study) EU Covenant of Mayors, 2023
  3. Fortum and Microsoft announce world's largest collaboration to heat homes, services and businesses with sustainable waste heat from new data centre region Fortum, 2022
  4. Katri Vala heating and cooling plant Helen, 2025
  5. Waste heat plays a significant role in a sustainable energy system Helen, 2023
  6. Bunhill Heat and Power: capturing waste heat from the London Underground Euroheat & Power, 2017
  7. New-technology heat pump plant starts at Eiranranta, recovering heat from water as cold as 5 C Helen, 2026
  8. Fortum has started heat production at two large data centre sites in Finland Fortum, 2026
  9. Kalundborg Symbiosis: six decades of a circular approach to production European Circular Economy Stakeholder Platform, 2024