Climate protection needs energy efficient data centers - Stulz GmbH

Energy Efficiency in the Data CenterT-1 T-2 T-3GUSVNPS Load++RPS networkEPS LoadUSV LoadFig. 11: Network structure according to load demands 15Data center air conditioning provides an interestingexample for the importance of the uninterruptible powersupply. Any interruption in the power supply is basicallyno problem for air conditioning equipment, as long asthe emergency power (EP) generator kicks in on schedulewithin 10 to 15 seconds. But problems may arise inthe EP system if the generator fails to start up. If the airconditioning in the computer room breaks down, thecomputers, disk arrays and servers could overheat duringthe shutdown, resulting in severe hardware damage. So itmakes sense to have the air conditioning at least partiallybacked up by the UPS system.• 6.3 Safe, energy-efficient UPS topologyEach component in the power supply chain to the loadsystem creates procurement and operational costs, eitherthrough losses or for maintenance and monitoring. As thefollowing presentation assumes an uninterruptible powersupply with no breaks (interruption = 0 ms), the supplyvoltage is converted twice by the power electronics ofthe UPS. The rectifier converts the incoming alternatingcurrent into direct current. This can then charge thebattery in the intermediate DC circuit as well as supplyingthe inverter input with the required power during normaloperations. The inverter converts the DC voltage intoclean, stable AC output voltage, which is, in turn, completelyunaffected by disturbances and fluctuations in thesupply voltage. Besides acting as a buffer in the eventof power failure, this so-called double conversion UPSalso provides optimal power quality which it continuallymonitors.Fig. 12 is a schematic showing the components of a typicaldouble conversion UPS with normal operational energylosses.However, a data center’s energy efficiency doesn’t have tosuffer if the following energy management configurationfor the air conditioning’s UPS-backup is used. Modern UPSequipment offers the option of using a “digital interactivemode” for air conditioning equipment, via digitalcontrol and a static bypass switch. This means that theair conditioning system can be powered directly from theAC input, bypassing the defective UPS power electronics.When problems occur in the power supply network, UPSmonitoring will ensure that the load is switched to thesafe, standby UPS power path.Input100%95%90%0%EfficiencycommunicationreactorrectifierRsmoothingreactorMfanelectronicsIinverterOutputoutputtransformerFig. 12: Schematic showing a UPS topology and how the componentsinfluence efficiency.27