Below the Vita Bergen park in Södermalm in Stockholm, the internet supplier Bahnhof has transformed an old rock cavity into a futuristic data centre, Bahnhof Pionen. The space now houses row upon row of cabinets, filled with computer equipment put there by Bahnhof’s customers. And the cabinets are heated up.
With increasingly densely packed and powerful hardware, a modern data centre becomes very energy intensive and the cooling system has to be dimensioned to handle this. When Bahnhof took over Pionen in 2007 and rebuilt the rock cavity into a data centre, conventional cooling equipment was installed.
The excess heat from the cooling plant facility was carried away by fans and released into the air outside the door to Pionen, where a characteristic plume of steam revealed that the business inside was wasting heat.
But already from the start, Bahnhof was thinking about doing something better with the surplus heat. There was enough surplus to provide heating to hundreds of apartments and Pionen is located in one of Sweden’s most densely populated areas, in Södermalm in Stockholm.