Assessment Leads to Investment in Free Cooling at Utah State University

Founded in 1888, Utah State University’s (USU) main campus in Logan, Utah, is home to roughly 20,000 students. USU is the state’s only land grant institution, offering 168 undergraduate degrees.

An EVAPCO eco-Air series V-configuration dry cooler was installed at the USU central energy plant to provide winter cooling capacity.

The campus saw massive growth during the 1990s with its endowment increasing by more than tenfold. It went from a small regional college to a nationally prominent university, even adding a campus – USU Eastern, in Price, Utah.

As the main campus expanded, so did the need for cooling capacity. A central energy plant was constructed in the northern part of the campus. This facility provides cooling to the bulk of the campus. Since its construction, however, freezing ambient conditions have created maintenance and longevity issues for the open-loop cooling tower system at the university. As a result, USU looked for alternative cooling system options. 

Utah State University’s main campus in Logan, Utah, is home to roughly 20,000 students.

Winter Cooling Tower Challenges

“Evaporative cooling capacity for the district system is provided by a six-cell, open-loop cooling tower capable of 6,000 tons,” said Reid Olsen, USU Central Energy Plant Manager, who has been at the university for 26 years. “This tower serves the condensers of the water-cooled chillers at the heart of the district cooling system. There are four chillers in all, two of which are rated for 1,800 tons each, and the other two are 900 tons apiece. The cooling towers reject heat from the condenser water loop via evaporative cooling, allowing the chillers to supply chilled water to the campus cooling loop.”

During heating season, the campus cooling load drops by more than 90%. For roughly half the year, only server rooms and a constant temperature room in the library call for cooling capacity. It’s during this time that the university’s maintenance crew battle to mitigate ice buildup damage to the 16-year-old cooling towers.

“We’re at about 4,500 feet above sea level here,” said Olsen. “It’s common that our outdoor ambient temperatures drop below -10°F (-23.33°C) and stay there for weeks at a time, and -30°F (-34.44°C) isn’t unheard-of.”

Since they were constructed, the cooling towers have been a winter maintenance challenge. Fill media within the towers freezes solid, building up so much weight that ultimately results in damage to the units. After a decade of this, several of the cells required complete fill media replacement at a tremendous expense, despite efforts to combat the issue.

“We stopped using the tower unless absolutely necessary,” said Olsen. “Warming up the condenser water by turning the fans off only lessened the damage. What we really needed was an entirely different solution for the winter months – one that would allow us to completely shut down the cooling tower during the winter.”

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