Aquifer Thermal Energy Storage District Cooling in Downtown St. Paul, Minnesota: Feasibility Study

摘要

Potential district cooling customers currently incur relatively low costs for cooling. Very little opportunity exists for district cooling to provide economic benefits by enabling customers to avoid capital expenditures for chilling systems. As an overall average, buildings are using an estimated 60% of the capacity of the installed chillers. The Prairie du Chien-Jordan aquifer is the most cost-effective aquifer for chilled water storage, but it is also the most heavily used aquifer in downtown St. Paul, so aquifer storage may interfere with other wells. Well interference can be minimized by placing storage wells near the Mississippi River. Daily chilled water storage can reduce storage well costs, in addition to increasing operational flexibility. Discharge water from existing winter heat pump operations can economically be used as the source water for winter chilling. Water chilling using ambient winter air can be done by cooling a brine in a cooling tower and then chilling water via a heat exchanger. Use of the steam pipes and tunnels can significantly reduce distribution system costs. However, there are significant legal barriers to access to the steam tunnels, and potential legal liabilities related to asbestos insulation. Although ATES can be cost-competitive compared to installing new chiller systems, ATES district cooling in the study area is not economically feasible. (ERA citation 12:047709)