Students at a Dublin technology university are enjoying an unexpected benefit from artificial intelligence: it helps heat their campus.
Since 2023, the Tallaght campus of the Technological University of Dublin has been part of a growing number of Buildings in the city’s southwest suburbs will 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 because the waste heat produced by these energy-hungry facilities is typically at too low a temperature to directly heat other buildings.
This is changing. As the AI boom begins and data centers are increasingly filled with racks of advanced chips that require up to triple the computing capacity of before, operators have had to find new ways to balance optimizing efficiency without sacrificing sustainability.
AI is the “twist” that makes it more attractive, according to Adam Fabricius, sales director at heating, ventilation and air conditioning equipment supplier Sav Systems, and a heat network researcher for its sister company EnergiRaven.
“What’s exciting is that AI can give you higher temperatures, and 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 “an extra social license,” Brendan Reidenbach of the International Energy Agency told CNBC.
“It may not be very cost-effective on paper, but it contributes to that good social impact by turning what is potential bad news of increased data centers into good news of what is ultimately decarbonized heat supply.” So it’s really a win-win situation,” he added.
Ireland, a “blank slate”
There has been good adoption among Big Tech. Microsoft announced plans to supply the Høje-Taastrup district heating network in Denmark; A Equinix a data center heats 1,000 homes in Paris; And Google announced an important heat recovery project at its factory in Hamina, Finland.
Ireland was one of two European countries to impose a moratorium on new data center applications as the power-hungry installations were putting strain on Dublin’s network, consuming 22% of the power of the small country in 2024. Ireland finally eased its moratorium late last year, as the AI boom led to a shift in sentiment about the economic potential of the facilities.
Ireland is “effectively a blank slate” because the country has never had a district heating system before, said the IEA’s Reidenbach. The Tallaght project shows the benefits of integrated planning because it brings together the electricity system manager and the distribution network manager, he said.
In 2020, local government established Ireland’s first not-for-profit energy utility, Heat Works. Waste heat from the neighboring AWS data center provides 100% of the heat to the grid.
“Although we are only in the second year of monitoring, we have evidence that the project has limited our exposure to market price shocks in general,” Rosie Webb, head of decarbonization at TU Dublin, told CNBC by email.
The campus reduced around 704 tonnes of carbon dioxide in 2024 despite the additional energy demand of two new buildings added to the site, according to calculations by TU Dublin.
AWS’ Tallaght data center offers a “unique opportunity” to reuse heat, according to Niamh Gallagher, the company’s national manager. The project, which allows AWS to provide recycled heat for free, 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 community’s climate goals,” Gallagher told CNBC.
Keeping Hot Fries Cool
When it comes to heat networks, Europe is much more advanced than the United States, according to Ben Hertz-Shargel, global head of grid edge at energy research firm Wood Mackenzie.
Some mid-sized data centers located closer to metropolitan areas are likely best positioned to provide waste heat, Hertz-Shargel said. He added that Equinix – which, like AWS, makes no profit from the waste heat it provides – is an example.
However, delays in obtaining permits and high investment costs of building heat networks and integrating data centers into the system make it difficult to scale the model.
There is also the life cycle mismatch. A district heating network typically has a lifespan of 30 years, Reidenbach said, while equipment inside a data center only has a lifespan of seven to 10 years. “This leaves a very large risk of stranded assets,” he added.
We view data centers as borrowers of energy, and actually producers of energy.
Kenneth O’Mahony
CEO of Nexalus
Nexalus, a thermal engineering and science company that patented its technology at Trinity College Dublin in Ireland, has been investigating ways to capture heat from hot GPUs and CPUs that data centers house.
The company uses jet impaction liquid cooling to improve chip performance while capturing waste heat at a much higher temperature. Instead of producing “low quality” heat, the system provides a temperature of around 55 to 60 degrees Celsius without using 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 their reuse much less practical, according to the company, which also maps heat coming from chips so it can target the hottest areas for cooling.
“It’s like a shower head in the shower. If you have a sore shoulder, you turn it to where you want it to go. That’s what we do, and we map it to maximize the impact on each of the individual chips,” O’Mahony said.
“We look at data centers as borrowers of energy, and actually producers of energy,” he added. “The desire should be for your data center to be integrated into the construction phase of cities, into the design of apartment buildings… producing enough heat for your entire building.”
Nexalus is not the only company exploring this technology. Nvidia recently set off alarm bells in the cooling market by unveiling its Next-generation Rubin chips which do not need to be cooled as much as previous models.
Rob Pfleging, CEO of Nautilus Data Technologies, a provider of modular liquid cooling systems, said he got “chills” seeing Nvidia’s announcement because he has long focused on increasing water temperatures to enable “significantly increased efficiency.”
“What’s Great About It [Nvidia] the announcement is [that it’s] “We’re moving in the right direction because it also now allows for much easier reuse of that heat,” Pfleging told CNBC.
The challenges ahead
Cities outside of Ireland are also looking to adopt such models. In October, British officials visited Denmark to see how data centers are connected to district heating networks and learn from the Nordic country’s success. The UK hopes to expand its heat networks to reach 20% of national heating demand by 2050, up from 3% today.
An analysis by EnergiRaven and Danish energy consultancy Viegand Maagøe found that waste heat from data centers could provide enough heat for at least 3.5 million homes by 2035 if heat networks were developed alongside AI infrastructure.
Using excess heat for community energy effectively uses electrons twice, argued Matthew Powell, who conducts research at EnergiRaven.
“Every kilowatt of energy we reuse represents a kilowatt of energy we don’t need to import,” Fabricius said, adding that if it replaces natural gas, it would make even more geopolitical and economic sense.
“You use it once for the calculation, and then you use the heat again to heat people’s homes that otherwise would have been generated from gas, if it was a boiler,” he told CNBC.
Asked about the risks of relying on a private data center for its core energy supply, TU Dublin said Tallaght’s district heating system was 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.
Nonetheless, the project now meets 92% of campus heating demand and, according to the university, has significantly accelerated TU Dublin’s progress towards its 2030 decarbonization targets.
District heating currently covers around 10% of global building heat demand, 90% of which comes from fossil fuels. For countries like the UK to benefit from reusing waste heat, we need to move away from gas and put the right infrastructure in the ground, said EnergiRaven’s Fabricius.
Diversifying systems “will probably be the best solution, but it’s going to be painful. It’s not going to be easy,” Fabricius said., but the UK, for example, is on the verge of saying “we actually need to do things differently”.
