Case Study: Wells Fargo's Free Data Center Cooling System
A cooling tower outside and a heat exchanger inside are expected to save the bank $450,000 annually.
November 5, 2007 12:00 PM ETComputerworld -
Bob Culver generated $150,000 in free cooling last year by using water-side economizer technology in the air conditioning system serving Wells Fargo & Co.s Minneapolis data center. Culver, vice president of technology information group facilities, expects to save double that amount this year and up to $450,000 annually as the bank continues to expand operations in the new, 80,000-square-foot facility. Thats a 15% overall savings on energy use not bad for an investment that added $1million (about 1%) to total construction costs when the facility was built two years ago. Its one of the better decisions we made, Culver says.
The water-side economizer uses a combination of a cooling tower outside the building and a shell and tube heat exchanger inside. For about four months each year, the system can provide water thats sufficiently chilled by outside air to allow the heat exchanger to directly feed Wells Fargos data center with cold air, bypassing the chiller. Savings this year will come from shutting off two chillers that currently feed the data center. Culver expects to add a third chiller in the next few years as the data center expands to full capacity.

Bob Culver
Free cooling starts to kick in when outside temperatures hit about 55 degrees, and it can bypass the chillers when temperatures drop to about 35 degrees, says John Smith, vice president at Michaud Cooley Erickson, a Minneapolis engineering consulting firm that worked on the Wells Fargo project.
Water-side economizers are less appealing in warmer climates, however, and may not fit neatly into existing data centers. Its somewhat expensive to retrofit, says Culver, who has looked into using the technology at Wells Fargos other facilities.
Adds Smith: While it can be done, it does require more mechanical space to contain the equipment, which would probably be difficult to incorporate into an existing facility.
But Wells Fargo does use whats called an air-side economizer in its Roseville, Calif., facility. An air-side economizer works well in temperatures that wouldnt be low enough to provide free cooling in a chilled-water design, Culver says. But the systems, which directly use outside air to cool a facility, arent effective in most data centers because it takes more energy to control the humidity level of incoming air than the system saves. Its a good fit in Roseville, Culver says, because humidity control isnt an issue thanks to the moderate climate. The economizer saves energy by reducing chiller loads, and it occasionally allows one of the sites two chillers to be shut down.
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