© 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.

Required fields: Comment, Name & Mail (Mail will not be published). Please also take note of our Privacy protection.