Students at a tech university in Dublin are enjoying an unexpected perk of artificial intelligence — it’s helping heat their campus.
Since 2023, the Technological University of Dublin’s Tallaght campus has been one of a growing number of buildings in the southwest suburban area of the city to be heated by waste heat from a nearby Amazon Web Services data center.
Data centers have always generated excess heat, but integration with district heating networks has been slow, as the waste heat produced by these power-hungry facilities is typically too low-temperature to directly warm other buildings.
That’s now changing. As the AI boom gets underway and data centers are increasingly filled with racks of advanced chips that require as much as triple the computing capacity of before, operators have had to find new ways to balance maximizing efficiency without sacrificing sustainability.
AI is the “twist” that makes it more attractive, according to Adam Fabricius, commercial manager at heating, ventilation and air conditioning equipment provider Sav Systems, and a researcher of heat networks for its sister company EnergiRaven.
“The exciting thing is that AI can give you higher temperatures, and the water cooling makes it a lot easier. You need a lot less hardware to connect these systems,” he told CNBC.
Providing heat to a district heating network gives data centers “additional social license,” the International Energy Agency’s Brendan Reidenbach told CNBC.
“It may not be ultimately very cost effective on paper, but it does contribute to that good social impact by turning what is a potential bad news story of increased data centers into a good-news story of what is ultimately decarbonized heat supply. So it’s very much a win-win situation,” he added.
Ireland a ‘blank slate’
There has been a fair uptake among Big Tech. Microsoft announced plans to fuel the Høje-Taastrup district heating network in Denmark; an Equinix data center heats 1,000 homes in Paris; and Google announced a major heat recovery project at its facility in Hamina, Finland.
Ireland was one of two European countries to enforce a moratorium on new data center applications as the power-hungry facilities strained Dublin’s grid, consuming 22% of the small country’s power in 2024. Ireland eventually eased its moratorium late last year as the AI boom saw sentiment U-turn on the economic potential of the facilities.
Ireland is “effectively a blank slate,” as the country has not had a district heating system before, said the IEA’s Reidenbach. The Tallaght scheme shows the benefits of integrated planning because it brings together the power system operator and the distribution grid operator, he said.
In 2020, local government formed Ireland’s first not-for-profit energy utility, Heat Works. Waste heat from the nearby AWS data center supplies 100% of the heat to the network.
“While we are only in the second year of monitoring, we have evidence that the project has limited our exposure to market price shocks generally,” Rosie Webb, head of decarbonization at TU Dublin, told CNBC via email.
The campus abated around 704 metric tons of carbon dioxide in 2024 despite the additional energy demand from two new buildings being added to the site, according to TU Dublin’s calculations.
AWS’ data center in Tallaght offers a “unique opportunity” to reuse heat, according to the company’s country lead Niamh Gallagher. The scheme, which sees AWS provide recycled heat free of charge, was initially planned to heat 55,000 square meters of public buildings, an area three times the size of the city’s Croke Park stadium pitch, as well as commercial space and 133 apartments.
“It’s a win-win when we can identify a special project that uses our infrastructure to support the climate goals of the community,” Gallagher told CNBC.
Keeping hot chips cool
When it comes to heating networks, Europe is far more advanced in comparison to the U.S., according to Ben Hertz-Shargel, global head of grid edge at energy research firm Wood Mackenzie.
Some medium-sized data centers that are located closer to metropolitan areas are likely in the best position to deliver waste heat, Hertz-Shargel said. He added that Equinix — which, like AWS, does not make a profit from the waste heat it supplies — is an example of this.
However, delays with permitting and the high capex costs of constructing heat networks and integrating data centers to the system make scaling the model challenging.
There’s also the life cycle mismatch. A district heating network is typically given a 30-year life span, Reidenbach said, while the equipment inside a data center is only given seven-to-10 years. “That does leave a very large risk of stranded assets,” he added.
We see data centers as energy borrowers, and actually as energy generating.
Kenneth O’Mahony
Nexalus CEO
Nexalus, a thermal and science engineering company that patented its technology from Trinity College Dublin in Ireland, investigated ways to capture heat from the hot GPUs and CPUs that data centers house.
The company uses jet impingement liquid cooling to enhance the performance of the chips while capturing waste heat at a much higher temperature. Instead of producing “low-grade” heat, the system delivers output at roughly 55 to 60 degrees Celsius without the use of heat pumps — hot enough to be reused directly for district heating, Nexalus CEO Kenneth O’Mahony told CNBC.
Other data centers typically release excess heat at around 30 to 35 degrees Celsius, making it far less practical to repurpose, according to the company, which also maps the heat coming off chips so that it can target the hottest areas for cooling.
“It’s like a shower head in the shower. If you’ve got a pain in your shoulder, you turn it to the spot where you want it to go. That’s what we do, and we map it out for maximizing the impact on each of the individual chips,” O’Mahony said.
“We see data centers as energy borrowers, and actually as energy generating,” he added. “The desire should be that your data center is embedded inside the construction phase of cities, the design of the apartment blocks … producing enough heat for your entire building.”
Nexalus isn’t the only firm exploring this technology. Nvidia recently sparked alarm in the cooling market when it unveiled its next-generation Rubin chips which do not need to be cooled to quite the extent as earlier models.
Rob Pfleging, CEO of Nautilus Data Technologies, a provider of modular liquid cooling, said he got “chills” when he saw the Nvidia announcement, as his focus has long been on raising water temperatures to allow for a “significant amount of more efficiency.”
“The great thing about that [Nvidia] announcement is [that it’s] moving in the right direction, because it also allows now for the much easier reuse of that heat,” Pfleging told CNBC.
Challenges ahead
Cities other than those in Ireland are also looking to adopt such models. U.K. officials in October visited Denmark to see how data centers are connected to district heating networks and learn from the Nordic country’s success. The U.K. hopes to scale heat networks to reach 20% of national heating demand by 2050, up from 3% today.
Analysis from EnergiRaven and Danish energy consultancy Viegand Maagøe found waste heat from data centers could supply enough heat for at least 3.5 million homes by 2035 if heat networks are scaled up in parallel to AI infrastructure.
Using excess heat for community power effectively allows electrons to be used twice, argued Matthew Powell, who conducts research at EnergiRaven.
“Every kilowatt of energy we reuse, there’s a kilowatt of energy we don’t need to import,” said Fabricius, adding that if it then replaces natural gas, it makes further geopolitical and economic sense.
“You’re using it once for the computation, and then you’re using the heat again to heat people’s homes that would have otherwise been generated from gas, if it was a boiler,” he told CNBC.
When asked about the risks of relying on a private data center for a core energy supply, TU Dublin said the Tallaght District Heating System is not dependent on a single source. The university is exploring geothermal energy and plans to incorporate a range of renewable sources to further diversify its energy mix.
Nevertheless, the scheme now meets 92% of the campus’s heating demand and, according to the university, has significantly accelerated TU Dublin’s progress toward its 2030 decarbonization targets.
District heating currently supplies around 10% of global building heat demand, with 90% of that total coming from fossil fuels. In order for countries like the U.K. to take advantage of repurposing waste heat, we need to move away from gas and get the right infrastructure in the ground, said EnergiRaven’s Fabricius.
Diversifying systems is “probably going to be the best way, but it’s going to be painful. It’s not going to be easy,” said Fabricius, but the U.K., for example, is at the point of saying “we actually need to do something differently.”
