NY-87-02-1 — Operating Experience with a Large Thermally Stratified Chilled-Water Storage Tank

A large chilled water storage tank, using thermal stratification to separate chilled water from warm return water, has been in full operation for about six years in a major office/courts complex in Vancouver, B. C. Operational data are presented showing the effectiveness of the chilled water storage tank in reducing or eliminating daytime chiller use. Two aspects of these data will be of particular interest. First, the very high percentage of total tank volume that is available for effective cooling in actual operation proves the validity of the thermal stratification design concept in chilled water storage. Second, the positive impact on the overall operation of the chilled water plant (chillers and storage tank) made possible by a series of energy conservation measures reinforces the importance of considering the interrelationships between systems in both design and operation. Operational limitations and guidelines applicable to this installation will be described. Finally, the paper includes observations concerning conditions inside the tank itself after several years of use.