The Big Chill

The planning process began in 2003, when Culver and his team worked with contractors, architects and consultants to design the facilities. Wells Fargo hadn't had excessively high energy costs in its other data centers, but with the new construction, Culver saw an opportunity to explore measures to lower consumption. That's become standard operating procedure for builders, so he and his team decided to run with it.

In the Minneapolis facility, Culver had to decide which kind of economizer to use. (Economizers are mechanical devices that help regulate energy usage.) One option was an air-side economizer, which uses air from outside the facility to cool the environment inside. But there was a downside: That would mess with the humidification needed to keep the air from becoming too dry, Culver says.

Instead, Culver turned to water-side economizers, which use evaporating water from a water tower to counteract heat emitted from servers. This method, known as "free cooling," let the company forgo chillers—machines that cool the water used to dehumidify the facility. That saved the company 300 kilowatts an hour per chiller, or about $150,000 a year so far, which Culver expects to double in the next two years.

The firm also looked into floor-level cooling for the Minneapolis data center. Many data centers use self-sustaining air conditioning units scattered around the floor and linked to chillers to distribute cool water. But Wells Fargo had eliminated the chillers, and for the density of servers in the facility, Culver and his team decided to go a different direction.

The engineering firm Wells Fargo had contracted for this project had built a central fan system for American Express, which had a lower-density data center. So Wells Fargo had the firm adapt that system to its new facility. The system is computer controlled and lets facility managers monitor how powerfully the fans operate at any given time. "It allows us to put the air where we need it," Culver says. "The system only works as hard as it needs to because it's regulated by the computer system."

And, he adds, it saved the company about 15 percent in power consumption.

In Tempe, though, Culver and his colleagues had to cope with an entirely different climate. Without Minneapolis' constant cooler temperatures, the Tempe facility wasn't a candidate for free cooling. So here the company used the modified floor-cooling system with variable- speed fans and chillers.

The controls in place at the two facilities have yielded impressive performance results: Both data centers have had 100 percent uptime since they went into operation, Culver says.