However, in Sonderborg, that heat does not vanish. Instead, it is captured in full. Through advanced liquid cooling technology designed by Danish engineering firm Danfoss, 100% of the waste heat generated by Bitten is recovered. This system replaces traditional air conditioning and fans that vent hot air outdoors. Instead, coolant is pumped directly over the high-temperature processing chips, absorbing the thermal energy. That heat is then channeled directly into Sonderborg’s municipal district heating network, helping to keep the town’s 75,000 residents warm.
This localized solution addresses a widening global crisis. The rapid expansion of AI data centres is placing massive strain on electrical infrastructure. There are currently more than 12,500 data centres around the world, with new facilities coming online daily. According to the International Energy Agency (IEA), data centres used 485 terawatt-hours of electricity in 2024. This equates to 1.5 percent of the world’s total energy supply, or roughly the total electricity generation of Germany. The IEA projects this figure will double to 3 percent by 2030, driven exponentially by AI development.
The energy implications are compounded by the fact that these facilities consume hundreds of billions of litres of water and contribute significantly to global warming. The United Nations Economic Commission for Europe has warned that the rapid expansion of AI “hyperscalers”—large-scale cloud service providers like Google, Amazon, and Microsoft—poses a “growing threat to electricity systems worldwide.” This tension is increasingly visible in political and social spheres. In the Netherlands, police arrested protesters against a new Microsoft data centre near Amsterdam. In Texas, residents have expressed anger over the relocation of AI and SpaceX operations to the state to take advantage of tax breaks, a move that occurred even as Texans voted for a Democratic senator in this week’s midterm elections.
The technical distinction between traditional cooling and waste heat recovery is critical to solving this problem. Kristian Strand, president of Danfoss Climate Solutions, explained that every digital action, from taking a picture to uploading a document, activates processing in a data centre, generating heat that must be removed. “With the waste heat recovery system, at the end of the process you basically have a tap of hot water coming out of the data centre,” Strand said. “That hot water can then be used not only to heat homes but in industrial processes, too.”
Scandinavia has emerged as a leader in this field, largely due to existing district heating infrastructure. Jan Rosenow, professor of energy and climate policy at the University of Oxford, noted that while the United States hosts the majority of the world’s data centres—approximately 4,000, drawing 5 percent of the nation’s electricity—very little heat is recovered there because there is no integrated network for it. “We should be building data centres where their heat can be used, not just where land is cheapest,” Rosenow said.
In Denmark, Meta’s data centre in Odense recovers around 100 gigawatt-hours (GWh) of heat annually, enough to power 6,900 homes. Similarly, Stockholm, Sweden, has been feeding data centre heat into its network since 2014. Danfoss engineers estimate that the heat wasted across Europe in a single year could power the entire city of Paris for 48 years. Globally, roughly two-thirds of all energy is expelled as excess heat, representing a vast untapped resource.
The application of this technology extends beyond data centres. At Sonderborg Hospital, Danfoss recently replaced two carbon-intensive gas boilers with a heat pump system that captures waste heat from medical equipment, including MRI scanners and temperature regulation systems in operating theatres. Previously, this heat was vented outside via cooling towers. Now, the hospital is energy independent for nine months of the year and can feed surplus heat back into the district network. Lasse Bo Madsen, head of technical services at the hospital, cited a strong business case for the transition. “The project will pay for itself inside two years, and it means we will be able to spend more money on patient care and new equipment, like scanners,” Madsen said.
As the AI boom accelerates, with new data centres demanding enough electricity to power small cities, the scalability of waste heat recovery presents a dual opportunity: reducing carbon emissions and easing the soaring demand that is stretching global supply. By converting thermal loss into a usable utility, the energy sector can transform a major liability into a sustainable resource, balancing the computational needs of the digital age with the physical limits of the energy grid.
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