{"46308":{"#nid":"46308","#data":{"type":"news","title":"Improved Techniques Will Help Control Heat in Large Data Centers","body":[{"value":"\u003Cp\u003EApproximately a third of the electricity consumed by large data centers doesn\u0027t power the computer servers that conduct online transactions, serve Web pages or store information. Instead, that electricity must be used for cooling the servers, a demand that continues to increase as computer processing power grows.\u003C\/p\u003E\n\u003Cp\u003EAnd the trend toward cloud computing will expand the need for both servers and cooling.\n\u003C\/p\u003E\n\u003Cp\u003EAt the Georgia Institute of Technology, researchers are using a 1,100-square-foot simulated data center to optimize cooling strategies and develop new heat transfer models that can be used by the designers of future facilities and equipment.  The goal is to reduce the portion of electricity used to cool data center equipment by as much as 15 percent.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022Computers convert electricity to heat as they operate,\u0022 said Yogendra Joshi, a professor in Georgia Tech\u0027s Woodruff School of Mechanical Engineering.  \u0022As they switch on and off, transistors produce heat, and all of that heat must be ultimately transferred to the environment.  If you are looking at a few computers, the heat produced is not that much.  But data centers generate heat at the rate of tens of megawatts that must be removed.\u0022\n\u003C\/p\u003E\n\u003Cp\u003ESummaries of the research have been published in the \u003Cem\u003EJournal of Electronic Packaging \u003C\/em\u003Eand \u003Cem\u003EInternational Journal of Heat and Mass Transfer \u003C\/em\u003Eand presented at the Second International Conference on Thermal Issues in Emerging Technologies, Theory and Applications. The research has been sponsored by the U.S. Office of Naval Research, and by the Consortium for Energy Efficient Thermal Management.\n\u003C\/p\u003E\n\u003Cp\u003EFive years ago, a typical refrigerator-sized server cabinet produced about one to five kilowatts of heat.  Today, high-performance computing cabinets of about the same size produce as much as 28 kilowatts, and machines already planned for production will produce twice as much.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022Some people have called this the Moore\u0027s Law of data centers,\u0022 observed Joshi, who is also the John M. McKenney and Warren D. Shiver Chair in the School of Mechanical Engineering.  \u0022The growth of cooling requirements parallels the growth of computing power, which roughly doubles every 18 months.  That has brought the energy requirements of data centers into the forefront.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EMost existing data centers rely on large air conditioning systems that pump cool air to server racks.  Data centers have traditionally used raised floors to allow space for circulating air beneath the equipment, but cooling can also come from the ceilings.  As cooling demands have increased, data center designers have developed complex systems of alternating cooling outlets and hot air returns throughout the facilities.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022How these are arranged is very important to how much cooling power will be required,\u0022 Joshi said.  \u0022There are ways to rearrange equipment within data centers to promote better air flow and greater energy efficiency, and we are exploring ways to improve those.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EBefore long, centers will likely have to use liquid cooling to replace chilled air in certain high-powered machines.  That will introduce a new level of complexity for the data centers, and create differential cooling needs that will have to be accounted for in the design and maintenance.  \n\u003C\/p\u003E\n\u003Cp\u003EJoshi and his students have assembled a small high-power-density data center on the Georgia Tech campus that includes different types of cooling systems, partitions to change room volumes and both real and simulated server racks.  They use fog generators and lasers to visualize air flow patterns, infrared sensors to quantify heat, airflow sensors to measure the output of fans and other systems, and sophisticated thermometers to measure temperatures on server motherboards.\n\u003C\/p\u003E\n\u003Cp\u003EBeyond studying the effects of alternate airflow patterns, they are also verifying that cooling systems are doing what they\u0027re supposed to do.\n\u003C\/p\u003E\n\u003Cp\u003EBecause tasks are dynamically assigned to specific machines, heat generation varies in a data center.  Joshi\u0027s group is also exploring algorithms that could help even out the computing load by assigning new computationally-intensive tasks to cooler machines, avoiding hot spots.\n\u003C\/p\u003E\n\u003Cp\u003EAnother issue they\u0027re studying is what happens when utility-system power to a data center is cut off.  The servers themselves continue to operate because they receive electricity from an uninterruptible power supply.  But the cooling equipment is powered by backup generators, which can take minutes to get up to speed.\n\u003C\/p\u003E\n\u003Cp\u003EDuring the brief time without cooling, heat builds up in the servers.  Existing computer models predict that temperatures will reach dangerous levels in a matter of seconds, but actual measurements done by Joshi\u0027s graduate students show that the equipment can run for as much as six minutes without cooling.  \n\u003C\/p\u003E\n\u003Cp\u003E\u0022We\u0027re developing models for different parts of the data center to learn how they respond to changes in temperature,\u0022 said Shawn Shields, a former graduate student in Joshi\u0027s lab.  \u0022Existing models consider that temperature changes across a server rack will be instantaneous, but we\u0027ve found that it takes quite a relatively long time for the server to reach a steady state.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EBeyond reducing cooling load, the researchers are also looking at how waste heat from data centers can be used.  The problem is that the heat is at relatively low temperatures, which makes it inefficient to convert to other forms of energy.  Options may include heating nearby buildings or pre-heating water, Joshi said.\n\u003C\/p\u003E\n\u003Cp\u003EData obtained by the researchers with thermometers and airflow meters is being used to validate computer models that are reasonably accurate, but run rapidly.  In the future, these models will help data center operators do a better job of optimizing cooling in real time, he said.\n\u003C\/p\u003E\n\u003Cp\u003EJoshi believes there\u0027s potential to reduce data center energy consumption by as much as 15 percent by adopting more efficient cooling techniques like those under development in his lab.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022Our data center laboratory is a complete sandbox in which we can study all sorts of options without affecting anybody\u0027s computing projects,\u0022 he added.  \u0022We can look at interesting ways to improve rack-level cooling, liquid cooling and thermoelectric cooling.\u0022\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\nGeorgia Institute of Technology\u003Cbr \/\u003E\n75 Fifth Street, N.W., Suite 100\u003Cbr \/\u003E\nAtlanta, Georgia  30308  USA\u003C\/strong\u003E\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contacts\u003C\/strong\u003E: John Toon (404-894-6986); E-mail: (\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E) or Abby Vogel (404-385-3364); E-mail: (\u003Ca href=\u0022mailto:avogel@gatech.edu\u0022\u003Eavogel@gatech.edu\u003C\/a\u003E).\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\n\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"Approximately a third of the electricity consumed by large data centers doesn\u0027t power the computer servers that conduct online transactions or serve Web pages. Instead, that electricity must be used for cooling the servers, a demand that continues to grow.","format":"limited_html"}],"field_summary_sentence":[{"value":"Researchers Use a Simulated Data Center to Study Cooling"}],"uid":"27303","created_gmt":"2009-06-02 00:00:00","changed_gmt":"2016-10-08 03:03:14","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2009-06-02T00:00:00-04:00","iso_date":"2009-06-02T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"46309":{"id":"46309","type":"image","title":"Measuring air temperature","body":null,"created":"1449174375","gmt_created":"2015-12-03 20:26:15","changed":"1475894416","gmt_changed":"2016-10-08 02:40:16","alt":"Measuring air temperature","file":{"fid":"101086","name":"trq71304.jpg","image_path":"\/sites\/default\/files\/images\/trq71304_0.jpg","image_full_path":"http:\/\/tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/trq71304_0.jpg","mime":"image\/jpeg","size":1514987,"path_740":"http:\/\/tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/trq71304_0.jpg?itok=Sd-bzEmF"}},"46310":{"id":"46310","type":"image","title":"Measuring air velocity","body":null,"created":"1449174375","gmt_created":"2015-12-03 20:26:15","changed":"1475894416","gmt_changed":"2016-10-08 02:40:16","alt":"Measuring air velocity","file":{"fid":"101087","name":"tkj71304.jpg","image_path":"\/sites\/default\/files\/images\/tkj71304_0.jpg","image_full_path":"http:\/\/tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/tkj71304_0.jpg","mime":"image\/jpeg","size":1708019,"path_740":"http:\/\/tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/tkj71304_0.jpg?itok=oKtGq2HL"}},"46311":{"id":"46311","type":"image","title":"Air circulation","body":null,"created":"1449174375","gmt_created":"2015-12-03 20:26:15","changed":"1475894416","gmt_changed":"2016-10-08 02:40:16","alt":"Air circulation","file":{"fid":"101088","name":"toz71304.jpg","image_path":"\/sites\/default\/files\/images\/toz71304_0.jpg","image_full_path":"http:\/\/tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/toz71304_0.jpg","mime":"image\/jpeg","size":1618079,"path_740":"http:\/\/tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/toz71304_0.jpg?itok=XMFocE9J"}}},"media_ids":["46309","46310","46311"],"related_links":[{"url":"http:\/\/www.me.gatech.edu\/","title":"George W. Woodruff School of Mechanical Engineering"},{"url":"http:\/\/www.me.gatech.edu\/faculty\/joshi.shtml","title":"Yogendra Joshi"}],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"153","name":"Computer Science\/Information Technology and Security"},{"id":"144","name":"Energy"},{"id":"145","name":"Engineering"},{"id":"154","name":"Environment"},{"id":"135","name":"Research"}],"keywords":[{"id":"439","name":"computer"},{"id":"437","name":"cooling"},{"id":"438","name":"data"},{"id":"436","name":"electricity"},{"id":"435","name":"heat"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cstrong\u003EJohn Toon\u003C\/strong\u003E\u003Cbr \/\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\u003Ca href=\u0022http:\/\/www.gatech.edu\/contact\/index.html?id=jt7\u0022\u003EContact John Toon\u003C\/a\u003E\u003Cbr \/\u003E\u003Cstrong\u003E404-894-6986\u003C\/strong\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}