DuPage County Governmental Center

Chilled Water Storage System, Design

Chilled Water Storage System, Design - Wheaton, IL


The primary goal of the project was to add 1,000 tons of cooling capacity to the central chilled water plant to accommodate the current and future growth of the county governmental complex. A secondary goal was to correct distribution problems with both the chilled and high-temperature hot water systems.


Source Award
1995 Excellence in Engineering Award, ASHRAE Illinois Chapter


  • Thermal energy storage (TES) takes the place of a 1,000-ton chiller to add additional on-peak cooling capacity during discharge. Chilled water at 42°F is generated off-peak by existing chillers.
  • TES is provided by a 150,000-cubic-foot, 10,000-ton-hour above-ground storage tank with new variable-speed transfer pumps and pressure-sustaining valves.
  • Existing chilled water distribution was converted to a primary/secondary/tertiary system with variable flow secondary and tertiary loops.