Press: Renewable energies cut PUE values

Energy efficiency is an essential measure for keeping costs under control in the data centre. As a rule, the level of efficiency is measured in terms of the PUE (power usage effectiveness) value. This represents the total consumption of a data centre in relation to the proportion consumed by the IT equipment. A PUE value of 2, which is common with conventional data centres, means that two kilowatts must be fed into the data centre for every one kilowatt of electricity needed by the server itself. This second kW is consumed by the IT infrastructure, mainly by the climate control. Cooling systems that provide cold water with the aid of renewable energies represent alternatives to electricity-powered cooling. They can drastically lower the PUE, as shown by two examples employing free cooling and geothermal energy.

Air and earth
At Leitz, based in Oberkochen, Germany, a free cooling unit with an enlarged heat exchanger generates cold water for an external temperature of up to 20°C. Rittal has also fitted the data centre with a wireless CMC-TC monitoring system. The sensors record the temperature at the servers and transmit this information to the management software that is responsible for the intelligent control. The software controls the climate control by either reducing the inlet temperatures or by increasing the pumping power. Depending on the outside temperature, the system can switch between free cooling and chillers within ten minutes. Even during summer nights, the use of chillers is sometimes no longer necessary, and this has helped cut costs by around 70 percent. The Oberkochen data centre has achieved a PUE value of 1.28 by using free cooling.

Engineers at Celler Brunnenbau took a different approach. The geothermal plant there pumps a mixture of water and glycol into the ground, from which it later re-emerges at the required temperature. This cold liquid is fed directly into the cooling circuit of Rittal's Liquid Cooling Packages (LCPs). The devices have their own temperature sensors and control systems, and are networked using management software by Simple Network Managing Protocol (SNMP). This regulates the pump at the well, based on the data from the LCPs: If it is sufficiently cool in the rack, the pumping power is reduced, while more cooling liquid is supplied to the cooling modules when the temperature is rising. This way, a PUE value of less than 1.1 can be achieved. In Celle, only the pump and the LCPs still consume electricity.

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Rittal

Rittal GmbH & Co. KG, which has its headquarters in Herborn, Germany, is one of the world's leading system suppliers for housing and enclosure technologies, power distribution systems, system climate control and IT infrastructure. Customers from all sectors of industry, from mechanical and plant engineering, as well as from the IT and telecoms market, are making use of system solutions from Rittal.

Its broad product range also includes complete solutions for modular and energy-efficient data centres: from innovative security concepts for data systems (formerly known as Litcos) through to physical data and system security for IT infrastructures (formerly known as Lampertz). The leading software providers Eplan and Mind8 - Rittal subsidiaries - are supplementing the Rittal product portfolio with interdisciplinary engineering solutions.

Founded in 1961, Rittal is now active worldwide with 12 production sites, 63 subsidiaries and 40 agencies. With 9,000 employees worldwide, Rittal is the largest company of the proprietor-run Friedhelm Loh Group of Haiger, Germany. The entire group employs more than 10,500 people and generated revenues of more than € 2.2 billion in 2008. Further information at www.rittal.com and www.friedhelm-loh-group.com.