A data centre is, thermodynamically, a heater that happens to compute. Every watt that goes into a server comes out as warmth, and the fastest-growing kind of computing — training and running AI models — is the hottest of all. Google has now announced what it will do with some of that heat: warm a town. It is investing roughly €1 billion ($1.1 billion) in its data centre at Hamina, on Finland’s south coast, and from 2025 the town’s energy company, Haminan Energia, will capture the exhaust heat from the servers and pipe it into the district-heating network that warms Hamina’s homes, schools and public buildings. Google says it will cover about 80 per cent of the district’s heating demand. It is the first time the company has done this anywhere.
Why now
Google has recovered heat inside its own buildings for a decade, but the scale has changed. AI has pushed data-centre electricity demand sharply upward — Google’s own emissions rose 13 per cent last year, largely for that reason — and the company has a public target of net-zero carbon by 2030 that analysts now openly doubt it can meet. Selling heat that would otherwise be vented is one of the few levers that both cuts a town’s fossil-fuel use and improves the data centre’s own accounts. Hamina is a good place to start: it sits on the Baltic, the site was a paper mill, and the servers are already cooled with seawater.
How district heating captures it
Finnish towns run hot-water pipes under their streets, fed by a central plant; buildings draw from the loop instead of burning their own fuel. Server halls run at 25–30°C; a heat pump lifts that to the 60–90°C the loop needs, and the electricity to do so is a fraction of what the servers consumed in the first place. Meta does something similar in Odense, Denmark; Microsoft is building the same in Espoo. In Nordic cities the question is no longer whether to use data-centre heat but how many data centres a heating network can absorb.
The version that fits Bangladesh
Nobody in Dhaka needs district heating. But the same physics runs the other way: Bangladesh’s data centres, including the national one at Kaliakoir, spend most of their electricity on cooling in a climate that never lets up, and the cheapest kilowatt-hour is the one not used. The relevant ideas from Hamina are the seawater cooling and the absorption chillers that turn waste heat into cold — the technology behind Singapore’s plans for tropical data centres, and the one any Bangladeshi operator building for the AI decade should be pricing now.
Why this does not show up in the efficiency number
Data centres are judged on PUE — power usage effectiveness, the total electricity drawn divided by the electricity that reaches the computers. A PUE of 1.1 means a tenth of the power goes to cooling, lighting and losses. It is the industry’s only widely quoted figure, and it has a blind spot: heat sold to a neighbour does not improve it at all.
A site can run at a PUE of 1.1 and throw every joule of its heat into the air, or run at 1.1 and warm ten thousand homes, and the number is the same. That is why waste-heat recovery spread in the Nordic countries first — not because the engineering is hard, but because the metric the industry optimises for gives no credit for it, and only a district-heating network that will pay for the heat makes the business case.
For any operator here, the lesson is in the order of events: the pipe has to have a buyer before the heat is worth capturing.
Source: The Verge, via Prothom Alo.
