The Ice Machine Cooling Chicago’s Skyscrapers: Inside Downtown Neighborhood Cooling Systems

ByShannon J. Cortes

Sep 1, 2022

CHICAGO – If you pass under the old Main Post Office on the Eisenhower Expressway, just across the river, you’ll see a nondescript building that’s easy to miss. The building appears to have a windowless concrete base and electrical equipment on the roof.

Most people “just don’t know exactly what they’re looking at,” according to Geoff Bares, an engineer who works indoors.

It is perhaps one of the most important buildings in the city. This is Centrio Plant #2, near the corner of South Franklin and West Van Buren streets.

“You don’t see our pipes running everywhere, so we’re very indescribable that way,” said Jim Rylowicz, CenTrio’s vice presidents of business development. “We make ice at night when the pressure on the power grid is lowest, prices are lowest.”

Center is a district energy company with operations in multiple cities. In Chicago, it operates the largest district cooling network in North America, helping to keep the city livable and functional when the mercury rises during the sweltering summer months.

“We serve downtown with chilled water for their cooling needs,” Rylowicz said. “Primarily air conditioning for their high-rise buildings.”

Air conditioning is becoming increasingly important as climate change affects our climate. The non-profit researcher Central Climate recently released data shows that Chicago summers are getting hotter, with an average of seven more summer days above normal temperature compared to the city in 1970.

Centrio takes the concept of “central air conditioning” and applies it to Chicago’s central business district.

A network of five plants spread across Chicago provides cooling for 115 downtown buildings, including icons like the Chicago Board of Trade, the Merchandise Mart and the former Main Post Office.

They are all connected to a closed loop of pipes.

Cities like Nashville, New Orleans, New York, San Diego, and Baltimore have adopted district cooling as a cheaper alternative to single-building air conditioning systems, but none are as extensive as Chicago’s system.

“We have the largest capacity in the United States,” Bares said. “There are a number of other systems, but we’re taking the cake.”

The Chamber of Commerce building is one of 115 included in the cooling network

This concrete base of Plant #2 contains an enormous storage tank measuring over 100 feet long, 90 feet wide, and 30 feet high.

The reservoir contains what you might call an industrial-size ice maker – 435 miles of tubing and 434 cooling coils.

“We have these machines called chillers,” Rylowicz said. “They can cool that water, or they can produce super cold glycol, it’s like antifreeze that’s pumped through tubes that are submerged in a reservoir of water, and on those tubes, ice gets form because of the super cold glycol flowing through them.”

CenTrio makes ice at night when demand on the electrical grid is lowest and cost is lowest by harnessing the power of thermal energy from ice.

“The thermal energy of ice is like any battery,” Bares said. “We charge our battery with thermal energy, as opposed to electrical energy.”