Data centres in the valley are learning to run cooler.
Walk into the main hall of the Brackenfield data centre, on the edge of the valley’s technology park, and the first thing you notice is what is missing. For years the building was known locally for the roar of its cooling fans, audible from the cycle path a hundred metres away. Today, standing between rows of servers, it is possible to hold a conversation without raising your voice.
The change is the result of a two-year programme to cut the energy the site spends keeping its machines cool. Brackenfield, which hosts computing for the regional health board, two universities and dozens of smaller firms, has reduced its electricity use for cooling by 38 per cent since the summer before last, saving roughly 1.9 million a year at current prices. Three other data centres in the valley are now following a similar path.
Running warmer to run cooler
The biggest single saving came from a counterintuitive decision: letting the halls run warmer. For most of the last decade, the air supplied to servers at Brackenfield was held at 18C, a margin that engineers now consider far more cautious than the hardware requires. The centre gradually raised the supply temperature to 26C, within the range manufacturers allow, and found no rise in failures.
Warmer halls mean the chillers, the large refrigeration units on the roof, need to work far less. For much of the year, the valley’s climate is cool enough that outside air, filtered and mixed, can do the job on its own. Last winter the chillers ran on only 41 days, compared with more than 200 two years earlier.
“We were cooling the building as though it were a freezer cabinet. Once we measured what the machines actually needed rather than what we feared they needed, the savings followed almost automatically,” said Ingrid Solheim, head of facilities at Brackenfield.
Ms Solheim said the team had also sealed gaps between server racks so that hot and cold air no longer mixed, and installed hundreds of small sensors to track temperatures rack by rack. Fans now speed up only where heat builds, rather than across an entire hall, which accounts for much of the drop in noise.
Liquid on the hottest chips
The newest hall goes further. Rather than blowing air over processors, it pumps water through thin metal plates fixed directly to the hottest chips, including those used for artificial intelligence workloads, which can draw several times the power of an ordinary server. The warm water that leaves the hall, at around 45C, is piped to a heat exchanger and used to warm offices on the technology park.
Engineers say that, by next autumn, the heat recovery system should supply around a third of the space heating for neighbouring buildings. Talks are under way with the council about extending the pipe to a planned housing development half a mile away, though the cost of laying new pipework under the main road is still being worked out.
Limits and questions
Not everyone is persuaded the gains are as large as claimed. Theo Marchetti, an energy researcher at the University of Calder, pointed out that the region’s data centres are using more electricity overall than they did three years ago, because demand for computing has grown faster than efficiency has improved. “A more efficient building is welcome,” he said. “But if you add a new hall every eighteen months, the grid still has to find the power.”
The regional energy agency has proposed that new data centres in the valley be required to publish their cooling efficiency each year and to connect to a heat network where one is available. Operators have broadly accepted the first idea and asked for more time on the second.
At Brackenfield, the next step is smaller and more mundane: replacing the old roof chillers with fewer, quieter units sized for a building that no longer needs them most of the time. Residents of the nearby cottages, who campaigned for years about the noise, say they have already noticed the difference on summer nights.
