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Cool and green: Citigroup’s Frankfurt Data Center

13 May 2015

In Frankfurt, Siemens helps optimize Citigroup’s data center. When it comes to building automation, security technology and power supply, the Siemens divisions Building Technologies and Energy Management deliver numerous customer
benefits through seamless cooperation that goes beyond divisional boundaries.

Frankfurt: the city with the highest density of data centers in Europe. In 2008, the German branch of Citigroup launched a particularly energy-efficient model, the Frankfurt Data Center (FDC). Thanks in part to solutions from the Siemens Building
Technologies Division, the building was awarded Leadership in Energy and Environmental Design (LEED) Platinum certification just one year after it opened, making the FDC one of the most energy-efficient data centers in the world.
Citigroup, the data center operator, and Siemens have continually enhanced, modified and optimized the deployed technology to meet the highest standards of availability, reliability, protection and energy-efficiency.

Growing along with the FDC
Availability and reliability are the top priorities in a data center like the FDC. This requires an uninterruptible and redundant power supply, intelligent safety and security technology and reliable building automation that cools and conditions the air
based on demand, thus keeping the servers from overheating. This is precisely why Citigroup has relied on the expertise and integrative solutions from Siemens for many years. “The request for proposal emphasized the importance of functionality and high availability,” explains Dirk Hatzmann, Senior Vice President of Technology Infrastructure at Citigroup. “But it was also important that our technical partners be prepared to grow along with the data center and its evolving requirements and respond flexibly to our needs.”

Redundancy, i.e. duplicate processes and data backups, high system availability and security as well as energy-efficiency are key elements for Citigroup when it comes to the operation of the FDC. “As IT director, reliability is especially important.
It starts with seemingly trivial things such as clear and correct server rack wiring, which supports operational transparency and saves time during maintenance, and goes all the way to the major things, such as uninterruptible power supply,” says

Redundancy in practice
Redundancy exists throughout the FDC. Processed data is stored in duplicate within the FDC and mirrored to other Citigroup data centers. In the building itself, a dual power feed from energy supplier Mainova, duplicate downstream medium- and low-voltage switchboards with duplicate switches and busbars from Siemens as well as
dual cooling technology ensure maximum redundancy. If a power failure were to occur, two independent uninterruptible power supply units and the emergency power supply would take over, ensuring continued power for at least 72 hours. This means that the FDC meets the Tier IV standard awarded by the Uptime Institute for maximum redundancy and 99.995 percent availability.

To guarantee the safety and security of the building and the processed data, all the installed Siemens security and safety systems were aligned with Citigroup’s global safety and security requirements. In addition to the technical requirements for fire safety and security technology, the regulations also include emergency concepts and provide for regular evacuation and safety drills with the fire department.

The Desigo building automation system from Siemens plays a central role in maintaining high energy-efficiency and the standards of the LEED certification. “Our motivation was to continuously save energy,” underscores Norbert Heberer of
Cofely Deutschland GmbH, the data center’s operator. “Building automation allows us to individually control and continuously monitor the heating, ventilation and cooling technology that is so vital to us.”

Ongoing technological enhancements
Since the Frankfurt Data Center went into operation, the installed technology has been continually enhanced. During ongoing operations, potential areas for optimization came to light that could be further exploited, such as in power supply
and building and security technology.

The data center is designed for thirty years of operation. The deployed solutions are not rigid but continue to grow along with the data center’s utilization. The planned power capacity of the FDC was 5 megawatts. In its current configuration, the
Frankfurt Data Center uses 5,000 m 2 of its 10,000 m 2 for server operation.

When operations began, the data center used 900 kilowatts of electricity. With additional utilization and occupancy, the electricity requirement now far exceeds 1 megawatt. “One challenge was to continually adjust the power supply and cooling capacity to the demand, from the planned 5 megawatts of total capacity to the actual starting load of 900 kilowatts and then to the current level of about 1.5 megawatts,” explains Heberer who supports the data center with ten employees over three shifts. “When operations started, we had a less efficient ratio of consumed energy to server energy demand, giving us a power usage effectiveness, PUE, of 2.8.”

Lowering the PUE value
To adjust the power supply and cooling capacity, technicians analyzed the complete electrical supply. They then worked with Siemens to optimize the cooling control. “Now all the dependencies of free cooling, pumps and chillers operate together as a bundle and can be controlled as demand dictates,” explains Heberer. To adjust
energy efficiency based on demand and lower the PUE value, lighting was tied to access control so the lights would turn on only when the server rooms are occupied. In addition, air conditioning in the server rooms was set to the optimal operating point so now less cooling capacity is needed. Air pressure in the cold aisle was also
lowered by 10 pascals. “During this project, we benefited from the experience and the commitment of the Siemens technicians. They were prepared to forge new paths and supported us quickly and competently, even with special solutions,” praises Heberer. As a result of this collaboration and the actions taken, the current PUE of
the FDC is 1.5. Over the next several months, Citigroup and its partners want to push it even lower.

In functional bids where individual disciplines are often considered separately, a certain amount of time is usually needed for adjustments, optimization and operating experience until the individual systems are harmonized and become an overall
solution. All the FDC stakeholders now benefit from custom solutions that were developed collectively. “Everyone involved in this project learned a great deal”, sums up Hatzmann. “Technology, solutions and processes now go hand in hand, and we are very satisfied. Above all, the dedicated technicians from Siemens made essential contributions to the project’s success.”

Marie Agaliotou