Purpose

To store chilled water produced at night using off-peak electricity for daytime distribution to downtown St. Paul district cooling customers

Provider

District Cooling St. Paul Inc., an affiliate of District Energy St. Paul, Inc.

Location

The first chilled-water storage tank is located adjacent to Hans O. Nyman Energy Center on Kellogg Boulevard; a second storage tank is located at 10th and Sibley Streets.

Benefits

• Increases efficiency of chilled-water production
• Increases reliability of the district cooling system
• Increases cooling capacity for Saint Paul, Minn
• Reduces regional peak electric demands
• Reduces use of CFC refrigerants and groundwater
• Improves regional air quality

Capacity

1994: 2.5-million-gallons of chilled water, enough to cool approximately 2 million square feet of building space
2003: Additional 4-million-gallons of chilled water

Construction and size

1994:Cylindrical steel tank, covered with insulation and an aesthetic shell, measuring 72 feet high by 80 feet in diameter
2003:Cylindrical steel tank, 90 feet in diameter and 90 feet high; design approved after extensive public input

Storage system funding

Funded by tax-exempt revenue bonds which are secured by long-term customer contracts and a utility rebate

Chilled-water storage systems elsewhere

Large chilled-water storage tanks are in use throughout the U.S., including a 4-million-gallon tank at 3M in Maplewood, Minn., and at Cornell University in Ithaca, N.Y.