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Reducing data center energy consumption

By Lars Strong, special to Network World
December 03, 2009 01:15 PM ET
This vendor-written tech primer has been edited by Network World to eliminate product promotion, but readers should note it will likely favor the submitter's approach.

Network World - While the acquisition cost for servers is declining, the total cost of ownership for housing, powering and cooling them has increased by 500% since 2000. Yet research from the Uptime Institute reveals that 60% of the available cooling in a typical computer room is wasted due to airflow losses, also called "bypass airflow."

The upshot: You are likely spending more money on energy than necessary because of the inefficiencies created by over-capacity and poor conditioned airflow management.

What does a real green data center look like?

But the good news is that optimizing your airflow represents the greatest opportunity for reducing operating costs and deferring capital costs. In addition, when you manage airflow more effectively, you can increase server density without adding new cooling infrastructure.

To optimize your existing computer room infrastructure, consider the following steps to resolve airflow inefficiencies:

1. Get a computer room cooling efficiency health check

If you have not embraced comprehensive data center monitoring -- documenting conditions such as utility load, equipment intake temperatures, UPS load, redundant cooling capacity and power usage effectiveness calculations -- a computer room airflow efficiency health check may be an appropriate place to start.

There are a range of diagnostic assessments available, and most will identify energy inefficiencies and offer a targeted remediation strategy. If followed, the plan could save you operating costs immediately, result in simple payback within a few months, and permit you the option of increasing server density sustainably.

At the very least, an expert computer room cooling health check should involve an examination of the following three aspects of data center health: IT equipment air-intake hotspots; percentage of bypass airflow; and cooling capacity factor (CCF), or the margin of installed cooling capacity vs. load.

To do this, the engineer will perform the following:

* Count and measure raised floor openings.

* Measure cabinet air-intake temperatures.

* Measure relative humidity of any identified hotspots.

* Sum cooling unit rated cooling capacity.

* Sum cooling unit rated airflow.

* Sum computing equipment power load in kW.

* Determine the presence of latent cooling and its associated latent cooling penalty.

* Check all return air temperature and relative humidity sensors for calibration.

These assessments will result in a remediation plan that will, among other things, likely advise sealing all cable and IT equipment cabinet openings to properly channel airflow.

Case in point: A company with a 6,996 square foot data center did a cooling efficiency health check by measuring bypass airflow and hotspots (cabinet intake-air temperatures which exceed maximums), and collecting data to calculate the CCF and make comparisons to the critical load.

By implementing the remediation strategy, the hotspots were eliminated and there was a 60% improvement in bypass airflow, which meant the reliability of the equipment would improve. In addition, because of improvements in airflow management, the company was able to put two cooling units into inactive standby mode, reducing electrical consumption by $27,024 per year ($2,252 per month based on $0.08/kWhr). Simple payback occurred between the second and third months.

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