The NTT data center in Frankfurt has one goal:
Save electricity during cooling
The amount of data worldwide is increasing exponentially, and with it the market for data processing and the data centers required for it is also booming. Modern data centers are inconceivable without cooling due to the extreme packing density of computers with their strong heat production. Both power supply and cooling are critical factors for the safe operation of such plants. Come what may, it’s a matter of saving electricity when cooling!
NTT’s data center campus, Frankfurt 1 Data Center, is one of the largest locations for data backup, colocation services to complex IT applications and cloud solutions with 60,000 sqm of data center space. The buildings are specially built and equipped for use as a data center. The site was chosen because of the maximum security and availability of infrastructure here. Important aspects here were, above all, the secure provision of electricity, connection to data networks and protection against natural hazards. To meet high customer demand, NTT Global Data Centers EMEA GmbH operates three additional sites in the Frankfurt region alone, which can provide additional space of over 50,000 sqm when completed.
The challenge lies in the cooling
One of the biggest challenges for NTT, in addition to the continuous and secure power supply, is the enormous waste heat from the computers running around the clock 365 days a year: In addition to the redundant power supply with additional emergency power generators or buffer batteries, an extremely reliable and equally efficient cooling system for the computer cabinets and all other critical areas is therefore necessary. On average, each kilowatt of computing power requires 0.2 to 0.5 kW of cooling power, and the necessary cooling systems are correspondingly large. To make the cooling process as safe and efficient as possible, NTT in Frankfurt relies on air cooling of the IT equipment with a central chilled water circuit for distribution within the building. Among other things, frequency converters from Danfoss Drives are used. The sophisticated concept covers every area from cooling air flow within the server rooms to the release of thermal energy into the environment.
Safe cooling at NTT: How it works
Christian Tietz, Sales Engineer at Danfoss Drives, explains step by step how the technology that cools the NTT data center works. Listen in and discover how variable frequency drives handle pump control. Since the systems were first commissioned in 2003, they have always ensured the optimum flow rate and controlled the motor characteristic curve of the pumps on the basis of a differential pressure measurement. In this way, the consumers are permanently supplied with the required amount of cold water.
The plant has both recooling units, which release waste heat or supply cooling water via the outside air, and chillers that can be switched on if the difference with the outside air is not sufficient during warm periods. The switching on takes place in stages in order to cool as energy-efficiently as possible. In the cold season, the outside air is often sufficient.
In addition to the frequency converters of the VLT series for cold and chilled water pumps, NTT in Continental Europe has been using Danfoss Turbocor exclusively as compressors in the installed chillers for about 2 years, in order to be able to benefit from the stepless speed control of the installed converter here as well. The resulting significant improvement in part-load efficiency is one of several factors that prompted NTT to take this step.
> 100,000 operating hours without failures
The frequency converters used optimize the running time of the pumps by changing the lead pump or the slave pumps according to the operating time. All components of the refrigeration system are connected to a control center via Modbus and are centrally controlled by it. This also allows the operating personnel to monitor the operating states of the individual system components at any time. If communication between the control center and the inverter should ever fail, the frequency inverters automatically switch to a maximum rated fixed speed to ensure cooling of the servers in any case.
NTT has been using Danfoss technology in Frankfurt since the data center was commissioned in 2003: In addition to the VLT HVAC Drives FC 102, VLT 6000 are still in use in some areas of the facility. According to the operator, they have probably run for around 100,000 operating hours – without ever causing any problems. The main power ratings used are 11/15 kW up to 37 kW in the order of about 60 frequency converters per building – a total of about 500-600 units.