Data center cooling: efficient and reliable with inverter

Tuesday, December 19, 2017

Low PUE in data center cooling saves energy and costs

Efficient data center cooling with inverter technology:
an International Provider of products for controlling indoor environments have recently installed a scalable data center together with one of their customers which has achieved the impressive Power Usage Effectiveness rating (PUE) of 1.21.
For security reasons we cannot reveal the name and the location of the data center since the information managed by the servers is in many cases very sensitive.

The installation consists of 6 phases each 500m² complete with 12 high efficient cooling units supplied by the International Provider. Each cooling unit has multiple inverter fans and compressors in order to minimize energy use and provide N+1 resilience. The units are designed to maintain the data center at 21°C ± 3°C and humidity between 20 and 80% RH. The inverter compressor technology, supplied by Danfoss, brings 3 very important benefits to the data center cooling system:

  • Low PUE contribution
  • Soft start
  • Quick and precise match to cooling demand

The efficiency of data centers is quoted as the PUE (Power Usage Effectiveness) rating and in a recent survey the average PUE rating of more than 500 data centers was 1.8. 

         Total facility power 

PUE = ---------------------------------
                IT equipment power

The International Provider installation has achieved a PUE of 1.21. The power needed for IT equipment of this size is 3.5 Megawatts. Meaning an estimated yearly saving of 1.5M€ per year, when using the PUE formula:

  • Power needed / year= 3.5 MW
  • Current PUE= 1,21 required by end-user and delivered by the International Provider
  • Average PUE= 1,8 in data center 
  • Difference in power needed= (1,8 - 1,21) x 3,5 MW (Current case versus average) 
  • Reduction of needed power= 2,06 MW
  • Reduction of annual electricity consumption= 2,06 x 1000 x 24 hours x 365 days= 18,09 Million kW/h (assumed 24hrs operation) 

Savings on electricity consumption= 0,08€/kW/h x 18,09 MkW= 1,45M€/year(1kW/h= 0.07 pounds or 1kW/h= 0,08 €)
Therefore the annual energy saving with the International Providers’ solution using Danfoss inverter scroll is worth 1.5M€ per year.

Significant economies are made with smaller generators

Reliability is a key word when it comes to infrastructures of IT operations. The power supply may be interrupted, and therefore there are always backup generators in order to tackle these incidents. Soft starter function is integrated into the inverter system which reduces the demand on the power grid and backup generators. Danfoss inverter compressors have an in-rush current near zero - that’s 70% of in-rush current reduction. 

The data center owner was also able to use significantly smaller generators in its installation thanks to the cooling units with Danfoss Inverter technology, offering considerable capital cost savings. 

Quick and precise temperature control
The requirements on the cooling system are quite wide, since the density in the data center changes in time. In general the units are only filled by 20% from the beginning and another module is only considered when reaching 80% of its capacity. 

It is in this environment and application that we are able to take full advantage of the benefits of the Danfoss Inverter compressors. With the use of Danfoss supplied electronic expansion valves, superheat controllers and sensors the International Provider is able to measure and control the capacity of the refrigeration system. The demand comes from the data center modules via the system controller (drive), which in turn controls the speed of the compressors to meet that requirement. It is this close control of the compressors that enables significant energy savings compared to fixed-speed compressors. The temperature never varies more than ±3°C.

International Provider engineering manager comments “in terms of efficiency this product is at the cutting edge and constant refining of the technologies, including the variable speed compressor system, is enabling us to further lower the PUE”. 

You can be sure with Danfoss expertise in compressor technology to get the best solution for your applications!

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