Turning Data Centre Waste Heat into a Public Energy Asset: The Tallaght District Heating Scheme

Background

As AI adoption accelerates, Europe is seeing a rapid expansion of data centres, facilities whose servers generate large amounts of heat as a byproduct.

In Tallaght, a suburb of Dublin, this waste heat is instead captured and redirected to heat homes and public buildings nearby. The Tallaght District Heating Scheme is owned by South Dublin County Council and was developed with the technical support of Codema, Dublin’s energy agency. The network now supplies a university campus, the council’s offices, a library, an innovation centre and 133 apartments, with further connections planned as the area continues to develop.

Codema and the Authorities Behind the Network

The project did not start with the data centre itself. In 2015, Codema mapped heat demand across Dublin to identify areas suited to district heating, and Tallaght emerged as a strong candidate. An early plan to anchor the network around a hospital’s combined heat and power plant fell through. The opportunity resurfaced once Amazon applied for planning permission to build a data centre nearby: local planning policy required new facilities producing significant waste heat to report its availability and install recovery equipment, bringing Amazon’s waste heat into the project as a usable resource.

South Dublin County Council had never operated a district heating network before, so Codema supported the project from the earliest feasibility studies onward. The agency also guided the council through a competitive dialogue procurement, narrowing nine interested companies to four, and helped assess technical proposals from energy companies across Scandinavia, the UK and continental Europe. The selected energy services company now designs, builds, operates and maintains the network under a ten-year contract, having contributed around 3 million euros upfront, repaid through a fixed monthly fee structured to keep it invested in the system’s long-term performance.

Funding came largely from the public sector: close to half from the Irish government, with further support from the EU’s HeatNet NorthWest Europe project, which also financed much of the early technical and economic groundwork. Construction began in late 2021, and the network has run since 2023. Codema’s role has continued well beyond construction: the agency still advises the council and HeatWorks, the company set up to manage the network, helping build expertise the local authority lacked at the outset.

From Server Heat to District Heat

Inside the data centre, server processors give off heat continuously as they run. Recovery coils capture this heat from the air and carry it as hot water to a nearby energy centre at around 25°c, where heat pumps raise the temperature further, to between 70°c and 85°c depending on outdoor conditions, before distributing it to connected buildings.

Because data centres operate around the clock, the available heat barely fluctuates throughout the year, making the network unusually stable compared to most renewable heat sources, which tend to vary with season or weather. The energy centre runs entirely on heat pumps and electric backup boilers, eliminating fossil fuels from heating across every connected building, and is estimated to save around 1 500 tonnes of CO2 annually. Because the delivered heat closely matches the temperature of a typical gas boiler, most buildings can connect without retrofitting their internal heating systems first.

A Mutually beneficial Project

For Amazon, supplying waste heat extends beyond regulatory compliance. The arrangement provides free cooling as a byproduct of heat extraction, reduces the company’s own electricity and water consumption, and offers a visible, concrete response to community concerns often raised by data centre developments. For the local area, the network turns a facility sometimes seen as a source of friction into a shared utility: homes, council offices and a university campus all draw heat from the same source, at a predictable cost, without relying on fossil fuels. The result is a tangible link between the data centre and the neighbourhood around it.

A Role in Grid Stability

The relationship between the network and Ireland’s electricity system runs both ways. Data centres already consume around 22% of the country’s electricity, a share expected to approach a third by 2030, placing real strain on a grid not designed for demand at this scale. South Dublin County Council and Codema are now exploring thermal energy storage that would allow the network to produce and store heat when electricity is cheap or abundant, including during periods of high wind generation, and draw on it later during peak demand instead of pulling additional power from the grid. Rather than only adding to the pressure data centres place on the system, the network could eventually help absorb some of it.

Strong Replication Potential

Tallaght’s success has directly shaped a second, larger project in Blanchardstown, where Codema is again coordinating data centre waste heat recovery, this time with three data centres competing to supply the network. Several other feasibility studies are underway elsewhere, with data centres increasingly considered as a heat source even outside Dublin.

Wider replication across Europe depends on a few conditions.

• New regulations can foster the development of such symbiotic projects across Europe, encouraging data centre operators to treat waste heat as a resource worth sharing.
• Local authorities need not be deterred by a lack of in-house experience, since Tallaght shows an energy agency can guide the process from early planning through to construction and beyond.

Regions with a high concentration of data centres, such as Dublin, are particularly well placed to match this surplus heat with genuine local demand, while easing the strain that growing data centre demand places on the electricity grid.