The Heat Is On

With triple digit temps, Duke's chilled water system pressed to keep campus cool

Duke's chilled water tanks cool water to about 40 degrees and pump it through 15 miles of pipes on campus to keep 70 buildings cool.
Duke's chilled water tanks cool water to about 40 degrees and pump it through 15 miles of pipes on campus to keep 70 buildings cool.

Darin Smith's job will be a little more difficult this week as temperatures climb into the triple digits. He's the person who manages Duke's chilled water system, which is responsible for keeping 70 buildings on campus cool. "Today will be a hell of a test," he said Wednesday, when temperatures reached 96 degrees with a heat index of 106. The National Weather Service is forecasting temperatures of 101 Thursday and Friday.Last week, Duke initiated its chilled water emergency response plan for the first time this year. The plan, which is a key element of operations at any large university in warm weather states, was put into play between six and eight days last year to help manage the demands on the system during extended periods of high heat and humidity during June, July, and August. The plan has three levels of management: level 3 indicates that demand has reached 95 percent of operating capacity, level 2 indicates that demand has exceeded operating capacity and reserve units are required, and level 1 indicates that demand has exceed total capacity and groups of buildings need to be taken offline - referred to as "load shed." "We've never had to load shed any building," Smith said. "That would only happen if something catastrophic happened such as a major electrical failure or we had a mechanical failure with more than one of our chillers."The plan includes contingencies to ensure that chilled water is always supplied to essential buildings such as the hospital, research labs, animal care facilities, Perkins Library and data centers. John Noonan, vice president for Facilities Management, said that if Duke ever reached level 1, the types of buildings that would be taken off the system would depend on the time of day, day of the week, and activities on campus during the summer months. "We would do our best to be flexible based on the unique circumstances," he said. "During a summer day, there are fewer people in the dorms and more people in classrooms and on the athletic fields, but at night people are moving back into dorms and fewer people are in classrooms." Kyle Cavanaugh, vice president for Administration said that Human Resources has a plan for how to manage staffing if buildings are taken off the chilled water system. "Staffing would depend on multiple factors such as how long a building was going to be offline, what time of day it was, and the temperature inside the building," he said.  "If temperatures inside a building became untenable and impacted normal work activities, we might look for other space available on campus or advise only employees in essential service positions in that building to remain at work."Cavanaugh, who also serves as Duke's emergency coordinator, said that the university would be monitoring the chilled water system closely during this latest heat wave and would coordinate campus-wide communication if load shedding became necessary. During the last 11 years, Duke has built an extensive central chilled water system that pumps cold water through 15 miles of pipes across campus to control temperatures and humidity for 10.5 million square feet of building space. In June, Duke added two more chillers to its system to help manage the additional demands of new buildings such as the Duke Cancer Center and the Duke Medical Pavilion currently under construction. While high temperatures can strain the chilled water system, Smith said that the combination of high humidity and heat can often create more problems. "Most university chilled water systems run water between 40 to 42 degrees," he said. "But when humidity is high, we try to operate our chilled water at 39 degrees. Colder water dehumidifies air better and the campus building systems can actually run with less horsepower."Smith said that managing the system during peak periods requires "a whole lot of help from some really talented people at Duke." "This is a team operation," he said. "We're watching the temperatures and working with people in the medical center and other units to juggle the load, make sure equipment is working properly and making decisions based on the situation."