© Bahnhof

Sweden’s coolest data center

The Swedish provider BAHNHOF converted a bunker in Stockholm into an unusual data center. Fans from ebm-papst keep the electricity bill just as cool as the location.


Thirty meters beneath Stockholm’s tranquil Södermalm district is one of the most secure – and extraordinary – data centers in the world. In a retired fallout shelter called Pionen, the data center operator BAHNHOF stores its customers’ data behind steel doors 50 centimeters thick. Extra protection is provided by surveillance cameras and a security service.

Data Center meets James Bond film

It is no accident that the room looks a bit like a scene from a James Bond film; the operators got inspiration from the legendary series of films when designing the interior of the data center. But instead of villains and their henchmen, Pionen is staffed by highly qualified employees working to store their customers’ data as safely and securely as possible.

Particle problems

That also includes high-performance air conditioning to dissipate the heat from the servers and supply them constantly with cool air. But for a long time, the air conditioning system was not a good fit with the operator’s high-tech philosophy as its CRAC units used inefficient, belt-driven fans. “A major disadvantage of belt drive is that the fans emit dirt particles, and that’s the last thing we need here,” says Kristian Thorin, project manager at BAHNHOF. “Sure, filters solve some of the problems, but there are still dirt particles in the server area. Besides, we had to do frequent maintenance, including the replacement of belts and filters. So we were looking for other solutions that would also allow us to save on energy costs. And that’s how we found ebm-papst.”

The operator worked with ebm-papst Sweden to develop a modernization plan for the data center. The plan included bringing the air conditioning system up to a level to match the reputation of Sweden’s coolest data center by installing EC fans, which feature especially high efficiency and easy control, to replace the belt-driven fans.

We don’t need any more filters and have been able to reduce the required fan pressure. That lowers our energy consumption even further.

Kristian Thorin, project manager at BAHNHOF

Once the plan was in place, a contractor carried out the upgrade and replaced all of the old fans with EC fans. “The upgrade went smoothly,” says Kristian Thorin. “Along with very high energy savings, we also solved the problem with the dirt particles. Now we don’t need any more filters and have been able to reduce the required fan pressure. That lowers our energy consumption even further.”

275 megawatts saved

All told, the upgrade saves BAHNHOF 275 megawatt-hours of energy each year, and it spends about 40,000 euros less on its annual electricity bill. The company operates its data center even more efficiently now that the waste heat from the servers is also put to good use. In the past, it was simply vented to the surface, but in a joint project with a district heating supplier, BAHNHOF installed two heat pumps in Pionen.

The upgrade saves BAHNHOF 275 megawatt-hours of energy each year.

They route the waste air from the servers to a 70-meter pipe that is connected to the district heating network’s main pipeline. Now the waste air from the servers provides private households with heat and hot water – a clever solution that would impress even James Bond’s master tinkerer Q.

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