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Roseville Skating Center and City Hall Feasibility Study September 23, 2007 9. RECOMMENDATIONS AND CONCLUSIONS The buildings on the Roseville City Hall campus have a diversity of heating, cooling and refrigeration loads. The Ice Arena and the Speed Skating Oval by their very nature must reject thermal energy whenever they are in operation. The Ice Arena operates year round and the Speed Skating Oval during the coldest winter months. The thermal energy that is now wasted to the outside air has significant value and can be used to provide space heating and hot water for all of the buildings on the campus. The buildings and mechanical systems on some of the buildings are relatively new and have been well maintained. Portions of the Maintenance Garage are only a few years old, as is the Public Safety addition to the City Hall and major renovations were completed within the last two years to the refrigeration system for the Oval. 9.1. The Ice Arena 1 Banquet Hall The refrigeration plant in the [ce Arena must be replaced and the HVAC equipment in the Banquet Hall is approximately 9-10 years old. One of the rooftop units has been replaced in the last 3 years. The replacement of the refrigeration plant presents an opportunity to integrate the HVAC system with the refrigeration system. The large intermittent peak cooling loads in the banquet hall are greater than the peak heating loads of the facility. This presents an opportunity to incorporate thermal ice storage into an integrated HVACR system. This will reduce summertime peak electrical loads by an estimated 25 kW, and reduce the size of the GHX required to service this building. A simple payback of 18 years can be expected for this facility. While this is not a quick payback, the system can become the basis for a larger integrated system that will reduce overall energy consumption of the other buildings on the city hall campus. 9.2. City Hall 1 Public Safety Building The two mechanical systems in the City Hall ! Public Safety Building are both comprised of large air cooled condensing units and gas fired boilers. Both systems have a VAV air distribution system with gas fired hydronic reheat systems. The energy costs in this building totaled approximately $110,500 in 2006 ($73,100 — electricity and $37,400 in natural gas). The installed cooling capacity in the City Hall is 50 tons (600,000 Btulhr) and in the Public Safety Building is 60 tons (720,000 Btulhr), for a total cooling capacity of 110 tons (1,320,000 Btulhr). The estimated peak heating load for this type of building typically ranges from 10 to 12 Btulhr per square foot. Including the parking garage under the Public Safety Building, the total are of the building is 67,660 square feet. The peak heat loss is estimated at between 670,600 and 811,900 Btulhr. The roof mounted cooling unit on the City Hall is relatively new and the Public Safety Building is less than four years old. This makes it difficult to justify the replacement of the equipment in the short term, but as the equipment ages and requires more maintenance, Geo-XergySystems Page 27 of 33