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2 3 � 5 � � d � � r5 1 �I 1� 7� 1� 15 1� �7 75 1 �] �� 21 �� 2� �� �� 2� �7 �� 2� �� ,� 1 �2 �3 �� �5 �6 ,} f �� 39 40 �41 �� �� �� �� ��6 �r ��3 �9 �� Ros�vi{�� Skating Center and City Hall Campus September23, 2007 ��CI�Tn�l� SUMMARY The City of Roseville, MN has a number of facilities, including the City N�lf / Public Safety Building, Maintenance Garage, Ice Arena / Banquet Hall, Fire Hall and Speed Skating Oval, located on a City Hall Campus. The Ice Arena refrigeration system was installed in 1969. It is a direct expansion, R22 refrigerant system that is being replaced in 2008. The City has asked Geo-Xergy Systems Inc. to review two options to replace the refrigeration system. The first option is to simply replace the direct expansion plant with a conventional refrigeration system and replace the existing rink floor system to operate with a secondary refrigerant. The second option is to determine the feasibility of a long-term plan to integrate the refrigeration system with the heating, ventilation and air conditioning system (HVACR) for the Ice Arena f Banquet Hall facility in the short term, and with other buildings on the campus on the longer term. The buildings on the campus currently consume 105,000 CCF, or the equivalent of 3,060,000 k�+h (EkWh) of natural gas annually, at a cost of $115,000. Electrical consumption totals 3,450,000 k1�'�� of electricity annually, at a cost of $250,000. An estimated 43% of the electrical consumption or 1,490,000 k'��91 is used by the refrigeration plant. The electrical energy plus the thermal energy removed from the ice surfaces produces approximately 3,725,000 EkWh of energy that can be used in the various buildings on the campus. This is more than is needed in the buildings to provide space and water heating. This energy is not always available when needed and cannot always be used when it is. A ground heat exchanger (GHX) can be built on the property and connected to the various buildings. Heat pumps can be used to replace the gas rooftop 1 air conditioning units, gas boilers, chillers and water heaters in the buildings. Because of the amount of thermal energy rejected to the GHX by the refrigeration plants the fluid temperatures will be much warmer than a conventional geothermal system. The heat pumps connected to the system will operate at a higher coefficient of performance (COP) than a conventional geothermal system. it is anticipated the cost of heating the buildings can be reduced by approximately 60% for an annual saving of $70,000 at today's utility rates. Further savings can be realized because of energy savings in cooling the buildings. Because of the need to replace the refrigeration plant in the ice Arena and the rooftop units are approximately 9 years old, there is an opportunity to build an integrated HVACR system. Since several of the buildings and mechanical systems are relatively new are well maintained, it will be more cost-effective to develop a long-term plan to integrate the various building systems when it is most appropriate and cost-effective. If the refrigeration plants in both the Ice Arena and the Speed Skating Oval are integrated into a common system using a GHX, there will be more thermal energy rejected into the ground in most years than is needed to heat the other buildings on the campus. There i$ an opportunity to connect additional buildings to the system. These buildings can be located on the campus, or possibly on other nearby building sites. An indoor or outdoor swimming pool would be a good example of a heating dominant building that could be connected to an integrated system. Snow melt on some of the sidewalks on the campus could also be considered. G�cr-��rgy Systems i