The author is Project Manager Silja Keränen from Kajaani University of Applied Sciences. The top photo of the blog is from the Renforsin Ranta business park in Kajaani. The photo was taken by Mikael Kanerva and the source is CSC.
The Utilisation of the Data Center Excess Heat project has been looking for solutions to utilise excess heat. Today, many new data centers that are built are relatively large, with a power of several tens or often even a couple of hundred megawatts. Large data centers also produce a lot of excess heat that could and should be utilised as much as possible.
Excess heat utilization has also been economically very profitable for data centers, because the data center has reached a lower electricity tax category if its excess heat has been utilised. The difference between the electricity tax categories is significant: the lower is €0.63 per MWh and the upper is €22.5 per MWh.
This will change from 1 July 2026, when, in accordance with the decision of Orpo’s Government, the data centers will move to a higher electricity tax category. However, a compensation element for the data centers is under preparation to refund part of this higher tax. The compensation element may possibly involve incentives for the excess heat utilisation, but the details are not yet known at the time of writing this article.
However, it is known that a diverse industrial ecosystem can develop around data centers. A preliminary outline of the project has been drawn up together with stakeholders in the Kajaani Otanmäki area.
In this industrial ecosystem, functions and actors have strong mutual synergies. The data center produces excess heat, which is utilised in the heating of premises. The greenhouse, located near the data center, can utilise excess heat in its heating, which is not only inexpensive but also low-carbon. It is estimated that a greenhouse of about 50 hectares in tomato production needs about 300 GWh of heat each year.
Greenhouse biowaste and other bio-based materials (e.g. growing media, tomato stems and leaves) can serve as input for a biogas plant. The plant, in turn, benefits from the excess heat in two ways: The biogas process works more efficiently when it is heated. The digestion residues from the biogas process can be dried and then recycled nutrients can be produced for agricultural use.
In addition, it has been tentatively searched whether carbon dioxide in biogas could be utilized in a greenhouse. Biogas is a collection of different gases containing the most methane (CH4) and carbon dioxide (CO2), as well as other gaseous compounds. Often biogas is further processed into pure methane, which has other potential uses in addition to energy use.
In greenhouse production, on the other hand, added carbon dioxide is used to ensure plant growth. No precedents were found for the use of CO2 separated from biogas in greenhouse production, but it is worth exploring further. In addition to greenhouse production, possible food production suitable for utilising excess heat may include, for example, fish farming or mushroom production. As the climate crisis progresses, food production conditions are deteriorating across the globe. This means that food production in the northern latitudes, which could be further developed and increased with excess heat, will increase in the future.
As part of the industrial ecosystem that forms around the data center, there may be many other ways to utilise excess heat. One interesting emerging field is the generation of electricity from heat, where the most potential technology is electricity production based on the ORC (Organic Rankine Cycle) process. There heat vaporizes the medium, and steam is used to generate electricity. This method would help the data centers to be more self-sufficient in electricity and, on the other hand, reduce the need for separate generation and transmission of electricity.
The application of technology to data centers is challenged by the relatively low temperature of excess heat, because the greater the temperature difference the better the efficiency. However, technology tends to develop, so it is very possible that heat-to-electricity production will become more common in connection with data centers in the future.
These and many other possibilities for utilizing the excess heat have been explored in the EU-funded Utilisation of the Data Center Excess Heat project. The funding has been granted by the Regional Council of Kainuu, and the project has been implemented by Kajaani University of Applied Sciences, CSC – IT Center for Science and LUKE Natural Resources Institute Finland. More information on the topic can be found on the project website and also on the Kajaani data center ecosystem website.
