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Roseville Skating Center and City Hall Feasibility Study September23, 2007 event of a power outage, and provides more consistent ice temperatures during peak use of the ice rink. In addition to helping maintain consistent ice temperatures during peak use of the ice, the cold mass beneath the ice surface helps freeze water quickly when the ice is resurfaced by providing a portion of the refrigeration capacity that is normally provided by the refrigeration plant operating with high flow rates through the rink piping. The cost of replacing the existing refrigeration plant with modular chillers and installing a new floor complete with the proposed "thermal storage buffer" (complete with insulation, under ice heating pipe and concrete surface) has been estimated at approximately $625,000. The table in Figure 22 shows an overall cost comparison between the installation of Option 1 and Option 2. There benefits of incorporating a"thermal storage buffer include: • Maintaining ice for extended periods in the event of a power outage • Reducing the capacity and power consumption of the pump needed to circulate chilled fluid through the rink surface to reduce both peak electrical demand as well as kV� consumption. * Lower pumping horsepower requirements reduces the refrigeration capacity required, further reducing electrical demand and power consumption requirements of the refrigeration plant by an estimated 7-10% • Improving the consistency and quality of the ice surface temperature. In discussion with several facility operators that have installed rink floors with a thermal storage buffer, there were several comments about the quality and consistencyof the ice surface. With the second option the existing refrigeration compressors will be replaced with several modular chillers that will be integrated with the heating, ventilation and air conditioning system of the Ice Arena / Banquet Hall. Thermal energy removed from the ice surface and the thermal storage buffer is stored in the GHX by circulating warm fluid produced by the modular chiller through the GHX rather than rejecting it to the outdoor air through a cooling tower. The earth around the GHX pipes is warmed with the energy removed from the ice, in effect storing large quantities of low grade thermal.energy. The energy stored in the ground is withdrawn by circulating fluid through the GHX and geothermal heat pumps located in the Banquet Hall or in adjacent buildings on the City Hall Campus. The temperature of the ground is much warmer than it normally would be because of the stored energy taken from the ice surface. Heat pumps operate at significantly higher efficiency when the temperature of the heat source is greater. For example, a heat pump using 40°� water as a heat source will operate at a coefficient of perFormance (COP) of 4.2, and the same heat pump will operate at a COP of 5.6 if the source water temperature is 70°�...an increase in efficiency of 33%. An integrated geothermal system includes a GHX that is used to store excess thermal energy that cannot be used immediately. The stored thermal energy can be used in the Ice Arena / Banquet Hall Facility, or can be used in other buildings on the campus. The size and cost of the GHX is determined by the amount of thermal energy storage that is available and the amount of energy that can potentially be used in the building and other nearby buildings. Geo-Xergy Systems Page 23 of 33