Can Off-peak Air Conditioning (OPAC) technology, improve the green energy profile of data centers? One of the major energy consumption categories of data centers is their need to keep all of their rows of rack mounted servers operating within their critical temperature parameters. The need to increase the efficiency of meeting a data center’s cooling needs is becoming ever more critical as rack power density (kW/rack) continues to rise. In fact, rack power density is up more than 5X in the past 10 years. Energy costs have now actually surpassed the server costs themselves as the highest single component of the overall cost structure of a fully-configured 1U server in a mission-critical (Tier IV) data center.

Many various techniques, such as advanced modular design, more efficient efficient Computer Room Air Conditioning (CRAC) units, usage of outside ambient air also called “free cooling” and so on are increasingly being adopted by data centers around the world in order to lower their overall cooling needs.

To find out more about an award winning green datacenter that is at the cutting edge of improving how it uses energy to use less read our post: “World’s Greenest Data Center Opens in Frankfurt am Mein“.

Can Off-peak Air Conditioning (OPAC) Technology Be Used in Data Centers?

An additional technology exists that I believe can help data centers improve their energy usage profiles by shifting energy demand to off-peak hours and in so doing significantly lower their energy consumption during critical periods of peak demand. Off-peak Air Conditioning (OPAC) technology is a way for data centers to improve their peak energy demand profile.

Off-peak Air Conditioning (OPAC) technology, especially those that incorporate robust ice thermal sinks, such as the award winning Ice Bear system produced by Ice Energy optimize the peak energy demand profile of a building’s cooling system. It accomplishes this by moving the required energy inputs for daily seasonal cooling needs from the peak demand hours of the day when the cooling requirements are usually also the greatest to off-peak demand hours.

In order to accomplish this these systems make use of a thermal sink, such as water ice that is frozen during periods of off-peak demand and that acts as an kind of battery, storing “coldness” which can be discharged over the hot daytime hours. Basically these systems use a heat exchanger that alternately pumps heat out of the thermal mass, during the energy consuming phase of the cycle and freezing water into ice during the late night/early morning hours; while using the same heat exchange to cool the structure during the day, by removing heat from the air and transferring it back into the ice that was produced during off peak hours.

Are any OPAC Enhanced Green Data Centers Out there?

I have not yet run across any examples of OPAC systems being employed by data centers and would be interested in hearing about them if they already do exist. I see this as yet one more way in which data centers can improve their green profiles, by shifting a portion of their energy needs from periods of peak demand to off peak periods when supply outstrips demand. The ability to shift power consumption to periods when supplies are most abundant compared to demand will also make better use of some renewable energy sources such as wind power — creating demand for the wind energy produced during the night hours when the wind also blows.

If anyone knows of examples of data centers that are using OPAC systems please let me know and I promise to profile them.

© 2009, Chris de Morsella. All rights reserved. Do not republish.

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Author: Chris de Morsella (146 Articles)

After a decade performing as a lead guitarist for rock bands, Chris de Morsella decided to return to the career his uncle mentored him in as a youth....Software Engineering. Since that time he has thrown himself into his work. He has designed a compound document publishing architecture for regulatory submissions capable of handling very large multi-document FDA regulatory drug approval submissions, for Liquent, a division of Thompson Publishing. At the Associated Press, Chris worked with senior editors at facilities around the world, to develop a solution for replacing existing editorial systems with an integrated international content management solution. He lead the design effort at Microsoft for a help system for mobile devices designed to provide contextual help for users. Chris also helped to develop the web assisted installer for LifeCam2.0, the software for Microsoft’s web cam and developed late breaking features for the product He also served with the Rhapsody client team to redesign and build a major new release of Real Networks Rhapsody client product. His most recent assignment has been Working with the Outlook Mobile Time Management team for the next release of Outlook Mobile for the SmartPhone. Chris' interests are in green building and architecture, smart grid, the cloud, geo-thermal energy, solar energy, smart growth, organic farming and permaculture. Follow Chris on Twitter.