As power costs soar and the demand for power in data centres grows saving energy is always going to be high on the to do list for man­agers, users and owners. Gartner have release an in depth report showing how to save up to 1 million kilo­watt hours per year.

The main areas for best prac­tice improve­ments are;

Plug holes in the raised floor: Most raised-floor envir­on­ments exhibit cable holes, conduit holes and other breaches that allow cold air to escape and mix with hot air. This single low-tech ret­ro­fit can save as much as 10 percent of the energy used for data centre cooling.

Install blank­ing panels: Any unused pos­i­tion in a rack needs to be covered with a blank­ing panel to manage airflow in a rack by pre­vent­ing the hot air leaving one piece of equip­ment from enter­ing the cold-air intake of other equip­ment in the same rack. When the panels are used effect­ively, supply air tem­per­at­ures are lowered by as much as 22 degrees Fahren­heit, greatly redu­cing the elec­tri­city con­sumed by fans in the IT equip­ment and poten­tially alle­vi­at­ing hot spots in the data centre.

Coordin­ate CRAC units: Older CRAC (com­puter room air-conditioning) units operate inde­pend­ently with respect to cooling and dehu­mid­i­fy­ing the air. These units should be tied together with newer tech­no­lo­gies so that their efforts are coordin­ated, or man­agers should remove humid­i­fic­a­tion respons­ib­il­it­ies from them alto­gether and place those respons­ib­il­it­ies on a newer piece of technology.

Improve under floor airflow: Older data centres typ­ic­ally have con­strained space under­neath the raised floor that is not only used for the dis­tri­bu­tion of cold air, but also has served as a place for data cables and power cables. Many old data centres have accu­mu­lated such a tangle of these cables that airflow is restric­ted, so the under floor should be cleaned out to improve airflow.

Imple­ment hot aisles and cold aisles: In tra­di­tional data centres, racks were set up in what is some­times referred to as “classroom style,” where all the intakes face in a single dir­ec­tion. This arrange­ment causes the hot air exhausted from one row to mix with the cold air being drawn into the adja­cent row, thereby increas­ing the cold-air-supply tem­per­at­ure in uneven and some­times unpre­dict­able ways. Newer rack layout prac­tices insti­tuted in the past 10 years demon­strate that organ­iz­ing rows into hot aisles and cold aisles is better for con­trolling the flow of air in the data centre.

Install sensors: A small number of indi­vidual sensors can be placed in areas where tem­per­at­ure prob­lems are sus­pec­ted. Simple sensors store tem­per­at­ure data that can be manu­ally col­lec­ted and trans­ferred into a spread­sheet, where it can be further ana­lyzed. Even this minimal invest­ment in instru­ment­a­tion can provide great insight into the dynam­ics of pos­sible data centres tem­per­at­ure prob­lems and can provide a method for ana­lyz­ing the results of improve­ments made to data centre cooling.

Imple­ment cold-aisle or hot-aisle con­tain­ment: Once a data centre has been organ­ized around hot aisles and cold aisles, dra­mat­ic­ally improved sep­ar­a­tion of cold supply air and hot exhaust air through con­tain­ment becomes an option. For most users, hot-aisle con­tain­ment or cold-aisle con­tain­ment will have the single largest payback of any of these energy effi­ciency best practices.

Raise the tem­per­at­ure in the data centres: Many data centres are run colder than an effi­cient stand­ard. ASHRAE (the Amer­ican Society of Heating, Refri­ger­at­ing, and Air-Conditioning Engin­eers) has increased the top end of allow­able supply-side air tem­per­at­ures from 77 to 80 degrees Fahren­heit. Not all data centres should be run at the top end of this tem­per­at­ure range, but a step-by-step increase, even to the 75 to 76 F range, would have a bene­fi­cial effect on data centre elec­trical use.

Install variable-speed fans and pumps: Tra­di­tional CRAC and CRAH (com­puter room air handler) units contain fans that run at a single speed. Emer­ging best prac­tices suggest that variable-speed fans be used whenever pos­sible. A reduc­tion of 10 percent in fan speed yields an approx­im­ately 27 percent reduc­tion in the fan’s elec­trical use, and a 20 percent reduc­tion in speed yields elec­trical savings of approx­im­ately 49 percent.

Exploit “free cooling”: Free cooling is the general term for any tech­nique that cools air without the use of chillers or refri­ger­a­tion units. The two most common forms of free cooling are air-side eco­nom­iz­a­tion and water-side eco­nom­iz­a­tion. The amount of free cooling avail­able depends on the local climate, and ranges from approx­im­ately 100 hours per year to more than 8,000 hours per year.

Design new data centres using modular cooling: Tra­di­tional raised-floor-perimeter air dis­tri­bu­tion systems have long been the method used to cool data centres. However, mount­ing evid­ence strongly points to the use of modular cooling (in-row or in-rack) as a more energy-efficient data centre cooling strategy

The entire report ($195) can be found on the Gartner Web site: “How to Save a Million Kilo­watt Hours in Your Data Center.”