Free cooling comes in the form of air-side and water-side economizers. With air-side economizers, often called fresh-air cooling, outside air is taken into a data center, usually filtered, and then used to cool the IT equipment. With water-side economizers, the outside air cools water in the outside chiller or water tower, which in turn cools a data center.
Both methods have become popular to reduce the electricity costs associated with mechanical refrigeration. Data center giants Google and Microsoft use free cooling where possible, and even smaller operations can use it to their advantage.Calculating the payoff
Canadian media company Quebecor Inc., for example, cools its 2,500-square-foot data center with air-side economizers. The economizers include baffles that open to varying degrees depending on the outside temperature and how much cooling a data center needs as well as three filters that pull bacteria-sized particulates out of the air and a humidifier to condition it for IT equipment. About 10% of the waste heat produced by the servers is then re-circulated to help condition the outside air that comes into a data center.
The Green Grid's online calculator includes a series of inputs -- location, temperature and humidity thresholds, IT load, and the cost of electricity are a few -- and at the other end spits out how many hours that data center can use air-side and water-side economizers, and how much money it could save.
A data center in Chicago, for example, with a 1 MW of IT load and a power usage effectiveness (PUE) of 1.6, paying 8 cents per kilowatt-hour and falling within ASHRAE's recommended temperature and humidity levels, can expect to save $20,000 a year by using air economizers for 660 hours, or $140,000 a year using water-side economizers for 4,861 hours, which is more than half the year.
In some parts of North America, such as northern Alaska and the far-north region of the Canadian province of Quebec, data centers can get as many as 8,000 hours of water-side economizing, which is more than 90% of the year. Other areas such as Miami, however, can only get 1,000 or fewer hours of water-side economizing.
The Green Grid, a nonprofit group, also created maps of North America with rough approximations of how many hours of economizing data centers can achieve in each location (fresh-air cooling image here, and water-side cooling image here). The free versions appear at a smaller resolution than the larger versions available for Green Grid members who want more detail.
"Fresh-air cooling and water-side economizers have become more popular," said Mark Monroe, a member of the Green Grid's board of directors and the director of sustainable computing at Sun Microsystems Inc. "This gives people a simple tool to get a quick estimate of how much free cooling they might be able to get with their data centers."
Let us know what you think about the story; email Mark Fontecchio, News Writer.