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FOCUS ENERGY EFFICIENCY


Issue 18, October/November


REDUCING ENERGY IN THE DATA CENTER Energy efficiency doesn’t have to be complicated, as Ramzi Namek explains


and efficient. The data center industry has come a long way since the 1970s to make these complex facilities more reliable and available. This article presents eight strategies to improve efficiency and reduce energy usage in the data center.


E 1. CONSIDER AIRFLOW MANAGEMENT


This is usually termed a ‘low-hanging fruit’ item, but it is quite a challenging improvement to achieve, particularly


if the data center


does not utilize a HAC/CAC (Hot Aisle Containment/Cold-Aisle)


layout. Sealing


openings in the raised floor will help increase the air pressure in the raised access floor and minimize wasteful leakage.


Installing blanking panels and plates in empty Us in an IT rack will reduce bypass air, where hot air is pulled back into the front of the servers. While most energy savings will be seen with a HAC/CAC layout, this may prove to be unachievable for a day-two audit in an existing data center. The reason is that shutting down live servers and moving them around may not be an easy task.


2. SPECIFY HIGHER WATER AND AIR OPERATING TEMPERATURES


Changing the common notion from ‘colder is better’ to a higher room temperature based on ASHRAE’s recommended thermal guidelines will result in significant energy savings. Raising the leaving chilled water temperature (LCHWT) is one strategy that will reduce chiller lift on the evaporator side and reduce total energy consumption.


With the strategies and chiller


proper CAC/HAC containment controls,


raising the


LCHWT to the low 60ºF (15ºC) results in power reductions in the range of 25-32%.


Other benefits of raising temperatures are as follows: (1) Setting air temperatures higher means less demand to cool the air streams.


72 www.datacenterdynamics.com


data centers was barely on anyone’s mind. Engineers designed and operated data centers wastefully


Before 2006, energy in


3. INCREASE THE TEMPERATURE DIFFERENCE FOR WATER AND AIR Another strategy to reduce power consumption is increasing the Temperature Delta (ΔT) between the entering and leaving water or air temperatures. This brings us back to the Affinity laws, whereby reduced flow due to a higher ΔT will result in a cube root reduction in energy.


There is at least a 6% energy reduction simply by operating the plant at a higher ΔT.


4. SPECIFY VARIABLE SPEED SYSTEMS AND HIGH-EFFICIENCY EQUIPMENT


A modern mechanical system without speed or capacity control is an energy hog. It is


Recommended Recommended Allowable


Class


A1 to A4 A1 A2 A3 A4


18O Temp


15 to 32O 10 to 35O 5 to 40O 5 to 45O


Figure 1. ASHRAE guidelines and recommendations


C to 27O C C


C C


C 5.5O


therefore prudent to integrate, where possible, variable frequency drives (VFDs) on pump and fan motors, as well as specify variable capacity


chillers. Specifying the highest


efficiency equipment within a family of manufacturers will also reflect in the overall reduction in energy usage.


5. EMPLOY AIR-SIDE OR WATER-SIDE ECONOMIZERS


The latest recommendations from the ASHRAE TC 9.9 adds two new classes to its allowable and recommended environmental conditions guidelines for data centers: A3, A4 expands the environmental envelope, while classes A1, A2, B and C remain identical to the 2008 version.


I urge you to read the full white paper. A tight thermal IT environment is a thing of the past.


Users who are not adopting air-side or water -side economization as part of their cooling solution are throwing money out the window.


RH


C DP to 60% RH and 15O 20% to 80% RH, 17O 20% to 80% RH, 21O


C DP


C DP C DP


8%, -12% DP to 85% RH 8%, -12% DP to 90% RH


ngineering is often perceived as the practice of applying scientific principles to achieve an end product that is reliable


This means lower fan energy. Raising the temperatures for either air or water increases the number of hours per year, where (2) water-side or (3) air-side economizers may be used. The compressor is either off or at partial loading during full or partial free cooling, and energy consumption is decreased. (4) In addition, smaller chiller power requirements may translate to smaller generator sizes that satisfy the electrical load of the building. In present-day energy lingo, all the above translate


to (5) smaller


Effectiveness (PUE) for data centers and (6) reduced carbon footprint for projects.


EIGHT MECHANICAL STRATEGIES TO


Power Usage Ramzi Namek, president, TSS Engineering PC


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