Below the campus sidewalks and streets lies a vast network of interconnected pipes that carry chilled water to approximately 180 buildings across campus.

This chilled water flows through the pipes seven days a week, 365 days a year, but is especially important during the hot and humid summer months, when it helps to keep a diverse array of campus buildings cool, from College Hall and the Hospital of the University of Pennsylvania to the Quad and Irvine Auditorium.

This chilled water system is a feat of engineering that originates at Penn’s two air conditioning structures, MOD 6 and MOD 7. The latter is the University’s most recent chiller plant, built in 2000. Designed by Leers Weinzapfel Associates, the intricate network of chillers, pipes, and cooling towers is surrounded by a grey mesh screen, made out of corrugated perforated stainless steel. The building is a dramatic mechanical structure on the south side of campus.

MOD 7 is also a highly efficient building, supplying 30,000 tons of chilled water around campus. The chilling process is centralized, explains Ken Ogawa, executive director of operations and maintenance for Facilities and Real Estate Services (FRES), because it is easier and more sustainable to maintain and operate a central plant as opposed to air conditioning units on each campus building.

“The systems are designed to operate at peak efficiency,” Ogawa says. “By having it centralized, we’re better able to operate the plants and support the cooling needs of campus as efficiently as possible.”

Water constantly circulates around campus in a closed loop of pipes that are connected to the chiller plant. MOD 7 not only cools down water, but also filters it and pushes it back through the pipes, where it is pumped into air handling units in campus buildings. Air handlers are similar to large boxed fans and contain chilled water coils. Water chilled to around 42 degrees passes over the surface of the coil. The fan pulls in air from the building, which passes over the surface of the coil, cooling the air to a comfortable temperature.

The cooling process for the entire campus is run out of Penn’s Operations Control Center (OCC), a central hub in Facilities’ Left Bank offices—what Walt Molishus, utilities operations manager in the Operations and Maintenance Department of FRES calls, “the nerve center of the campus.”

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Molishus and his team monitor air conditioning, as well as steam and electricity usage through a complex computerized Supervisory Control and Data Acquisition (SCADA) System. They are able to control the chiller plant remotely, as well as oversee the temperature and pressure of the chilled water as it is pushed into buildings. The team can also monitor the temperature of the water as it is returned to MOD 7.

“That gives us some kind of idea and feedback about what’s happening on campus,” Molishus says. “Compared to what I’ve seen at most universities, this system is pretty sophisticated.”

On extremely hot days, the team works to reduce load as much as possible during peak hours of electricity usage. They conduct rolling air handler shutdowns and advise building administrators, eco-reps, and other occupants to shut off or sparingly use electrical appliances.

“Campus community members can make a difference by working with our operators,” says Ogawa, who notes that the Penn community can monitor campus-wide electricity usage and wholesale pricing online. “Sharing in the responsibility of managing our utility usage helps support the University’s Climate Action Plan goals and ultimately cost savings that lead to a unified bottom line.”      

FRES plans to expand the capacity of MOD 7 in the next several years, adding two 5,000-ton chillers, which will bump up the plant’s capacity to 40,000 tons of water and increase energy efficiency. Unlike the current machines, which run on electricity, the new machines will be steam-powered as part of a larger diversification of Penn’s energy resources.