Why heat reuse starts with planning

Why heat reuse needs to be planned into data center development from the start 

By Hrefna Haraldsdóttir, atNorth, and Ulrika Jardfelt, Calentix

Heat reuse has become a key opportunity for data centers to contribute to the communities around them. But making that opportunity work depends on decisions made well before heat becomes available.

The partnership between Calentix and atNorth, at the SWE04 data center in Sollefteå, explores these factors and demonstrates how an innovative business model can help turn heat reuse opportunities into viable infrastructure projects in practice. 

Having heat available is only the beginning. For a heat recovery project to work, there needs to be an opportunity for the surplus heat to create value, the right infrastructure between the two, a technical solution that works for both systems and a commercial model that makes sense for everyone involved. 

These factors are highly dependent on local circumstances. 

Building resilience through early planning 

From a district heating perspective, the value is created when the recovered heat is replacing more expensive or higher emission production. The value needs to be enough to carry the cost of the infrastructure, which means proximity is particularly important. The closer the heat source is to the network, the lower the infrastructure investment required to connect the two. There also needs to be sufficient demand and the temperature and characteristics of the available heat need to be made compatible with the receiving system. 

This is why heat reuse cannot be treated as a standard solution that can simply be added to every data center project. It needs to be considered in the context of the location, the surrounding energy system and the needs of the community. 

This approach builds on atNorth’s experience with heat reuse partnerships in other regions. atNorth’s SWE01 site in Sweden is a good example of this, as it repurposes surplus heat from the data center cooling process in collaboration with Stockholm Exergi, the local district heating provider to warm local homes and businesses – a similar partnership with Vestforbrænding in Denmark will deliver heat to over 8000 homes. Conversely, in Finland, collaboration with Kesko Corporation enables recovered heat to warm a neighboring supermarket. atNorth’s newest initiative at its DEN02 campus extends this model further, with surplus heat that will power Selected Group’s greenhouse development – supporting low carbon, year round food production and strengthening Danish food security.  

Building on this experience, atNorth decided to explore a new way of working, this time together with a partner dedicated to developing heat reuse projects and establishing an innovative business model as an independent heat producer – that partner is Calentix.  

Collaboration: From feasibility to development at SWE04 

At SWE04, an early feasibility study carried out in partnership with Calentix, confirmed that heat recovery is technically feasible and that there is local interest in exploring the opportunity further, including supplying heat to the nearby Långsele district heating network. atNorth and Calentix have now signed a Project Development Agreement, with Calentix leading the development of the potential heat recovery solution across technical, commercial and financial aspects. atNorth will provide access to the surplus heat from SWE04, together with site integration and the necessary infrastructure interfaces. 

The focus now is on the detailed work required to understand whether the project can become technically and commercially viable; including technical design, site planning, commercial principles and the agreements needed between the different parties. 

With the data center and the district heating network operating within two very different systems, a core challenge is finding a solution that creates value for both sides. 

Connecting the two requires infrastructure, investment, technical expertise and a commercial framework that works for everyone. 

atNorth’s role in the collaboration is to make the surplus heat available, Calentix takes responsibility for developing and financing the project to recover and transport it to where it creates value. This allows each partner to focus on what they do best, while creating a practical way for the heat to be used within the local energy system and demonstrating how collaboration between specialist partners can make a difference. 

Calentix specializes in developing the technical and commercial framework necessary to connect the data center with district heating systems. It brings together the technical expertise, aligning all parties and supplying the financing needed to develop, build and operate heat recovery systems, creating a dedicated role as an independent heat producer placed between the data center and district heating operator. 

Planning for the ecosystem around the data center 

There is also a broader reason to consider heat reuse ahead of the development process. 

A data center does not operate in isolation. It sits within an existing energy system, community and local economy. The opportunity to reuse surplus heat creates potential for the facility to contribute to those systems as well as consume resources from them – a circular approach that is encouraged in the Nordic region. 

At SWE04, the potential connection to Långsele’s district heating network is an example of that wider thinking. By repurposing surplus heat from the data center as a local energy resource, the data center could contribute to a more resource-efficient heating network. This approach aligns with Sollefteå Municipality’s adoption of local sustainability and climate objectives under its Hållbara Sollefteå program that aims to significantly reduce greenhouse gas emissions from municipal operations, work towards climate-neutral transportation, increase the use of renewable energy, and pursue a goal of being climate neutral by 2045. 

For atNorth, considering heat reuse at an early stage is important, because it highlights the role a facility can play within its surrounding community and energy ecosystem. For Calentix, working with atNorth and the local district heating operator, Adven – two parties with experience of heat recovery – is an opportunity to further develop a scalable heat recovery solution that connects existing local infrastructure and respond to genuine local demand. 

As data center deployment continues to accelerate, the timing of these conversations will become increasingly important. The opportunity is not simply to find more uses for surplus heat, but to ensure its integration into wider energy system planning. To achieve this, the most important change may be to start planning for it sooner.