High Impact Measures to Boost Data Center Efficiency (Part 1)

With Data Center energy consumption at an all time high, maintaining the lowest possible total cost of ownership has become increasingly difficult.  We’ve detailed some high impact measures to help improve efficiency, and reduce power and cooling requirements to create a greener, more cost effective Data Center.

The first step in energy-efficiency planning is measuring current energy usage.  The power system is a critical element in the facilities infrastructure, and knowing where that energy is used and by which specific equipment is essential when creating, expanding, or optimizing a Data Center.

In order to understand how energy efficiency measures affect energy consumption in the Data Center, a baseline needs to be established for the current energy used. There are currently two primary metrics being used by a number of organizations such as the Green Grid to promote the notion of measuring Data Center energy efficiency. The first is Power Usage Effectiveness (PUE) which is defined as the total facility power consumed divided by the IT equipment power consumption. The second metric is PUE’s reciprocal known as Data Center Infrastructure Efficiency (DCiE) which is defined as the IT equipment power consumed divided by the total facility power consumption.

Total facility power is defined as power measured from the utility meter or switch gear solely dedicated to the operation of the Data Center infrastructure in the building if the building is a shared facility with other functions. This includes power consumed by electrical equipment such as switchgear, UPSs (uninterruptible power system) and batteries, PDUs (power distribution units), and stand-by generators. Mechanical equipment dedicated to the HVAC needs of the Data Center such as CRACs (computer room air conditioning units), chillers, DX (direct expansion) air handler units, drycoolers, pumps, and cooling towers. IT equipment power includes the loads associated with IT processes including server, storage, network, tape and other processing equipment fed through Data Center infrastructure support equipment such as PDUs, RPPs (remote power panels), or other distribution means fed from a UPS.

To collect the information noted above, an effective building management system (BMS) should be employed to help collect, categorize, and trend the data gathered. Most systems offered by BMS providers such as Johnson Controls, Andover, Automated Logic, Honeywell, Siemens, and others can allow monitoring of energy consumption for both the IT equipment and the associated infrastructure equipment serving the Data Center. Metering and other DCPs (data collection points) should be provided at all switchgear relating to power and mechanical needs of the Data Center. Also metering should be provided at the output side of the UPS modules or better yet the PDUs. This will provide the energy consumption rates of both the facility power and IT equipment power.

The types of electrical monitoring which can be employed to measure this type of information can be broken down into three basic forms:

  • Amperage-only monitoring
  • Estimated Wattage monitoring
  • True RMS Wattage monitoring

Amperage-only and Estimated Wattage monitoring means can be flawed in the information they provide due to the inaccuracies of measuring the sine wave and its form. Should a sine wave be produced inaccurately, as many double conversion UPS systems do, averaging means of formulating power consumption can prove to be flawed. True RMS Wattage monitoring provides a much more accurate means of understanding the idiosyncrasies of power consumption relating to data processing power sources. BMS systems which employ measures such as wave form capture sampling using real time updating provide a very high degree of accuracy. It should be pointed out that this type of monitoring can be expensive at implementation based on the number of locations it is determined to be used. Should the decision be made to measure power at the distribution level of PDUs and CRAC units to determine power consumption, the cost at this level can be higher than if monitoring was to be placed at the distribution panel boards feeding these types of devices. As long as all the IT equipment and associated infrastructure equipment is being fed from a singular (or dual) location, this monitoring may be far less expensive while still providing nearly the same information for the distributed systems required out in the Data Center.

Traditional Data Centers which are not currently enacting any type of energy efficiency measures are operating with an average PUE of over 3.  A Data Center which is actively pursuing energy efficient measures can achieve much lower ratings, and in return realize substantial energy savings.