How Duke Stays Cool During Heat Waves

Chiller system pumps water across campus to keep buildings cool

When temperatures in the Triangle set a record for most consecutive days at 100 degrees or more in the beginning of July, students, faculty, staff and visitors wouldn't have known it unless they stepped outside.

That's because Duke's chilled water system makes sure things stay cool inside.

The system constantly pumps 38.5-degree water through 15 miles of pipes across campus to control temperatures and humidity in 80 Duke buildings - even during triple digit heat for six-straight days, which struck the area July 3 to 8.

"We're constantly looking at the weather and checking the five-day forecast so we know what to expect," said Darin Smith, project manager for Duke's chilled water system. "We're always monitoring the system and making sure things are running to keep the campus cool."

Just as North Carolina was finishing a heat wave in June, Duke's Facilities Management was bringing online two new chillers to bring its total number to 23 for the system that features chillers on East and West campuses. So when temperatures hit 104 degrees on June 29, a new chiller helped keep things cool in buildings across campus. Smith said thanks to the new additions, Duke is able to withstand the hottest days Durham has seen this summer.

Two main chiller plants supply up to 42,000 tons of cooling capacity, which is the equivalent of keeping about 14,000 two-story homes cool. Additional "satellite" chillers offer another 5,000 tons of capacity. The most cooling Duke has needed this summer was 34,000 tons on June 29.

Duke is ready with a chilled water emergency response plan, a key element of operations at any large university in warm weather states, Smith said. Despite increasingly warm summers in recent years, Duke has never had to initiate the plan.

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."

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. If any buildings were ever temporarily forced off chilled water, Smith said that temperature and humidity would slowly rise in those selected areas, but Facilities would coordinate the movement of any faculty, staff, students or visitors to nearby buildings that could still provide cooling.

"With our new chillers online, we're now ahead of the game to the point where there wouldn't be a problem," Smith said. "We purposefully leave enough cushion so if weather got bad, no one would notice the difference."