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Roseville Skating Center and City Hall
<br />Feasibility Study September 23, 2007
<br />When fluid in the GHX is circulated through water source heat pumps, thermal energy
<br />can be either extracted to or rejected from the fluid. When heat is extracted from the fluid
<br />the GHX is an energy source for the heat pumps.
<br />Heat pumps operate at a coefficient of perFormance (COP) of 3.0 to 4.0 when extracting
<br />thermal energy from fluid that is 32°F. When a heat pump is operating at a COP of 4.0
<br />this means that 1.0 unit of electricity is used to power the equipment and 3.0 units of
<br />thermal energy are extracted from the fluid circulating through the heat pump. Since only
<br />the electricity is purchased and the energy in the GHX is free, each f�J'!i� of electricity
<br />produces 4.0 units of thermal energy. If the cost of electricity is $0.064, the cost of
<br />heating a building is $0.0641 4.0 =$0.016 per kVllh. In 2006, the cost of natural gas
<br />used on the City Hall Campus averaged $0.0376 per �kWh. The cost of heating a
<br />building with a geothermal system operating at a COP of 4.0 is only $0.0161 $0.0376 x
<br />100 = 42% of the cost of heating the building with natural gas.
<br />When the GHX temperature is higher, the heat pump operates at a significantly higher
<br />COP. When the GHX temperature is 60°F to '70°�, a heat pump will operate at a COP as
<br />high as 5.0. This reduces the cost of heating to $0.064 1 5.0 =$0.013 per kWh. In
<br />comparison to natural gas this provides a saving of $0.0131$0.0376 x 100 = 35% of the
<br />cost of heating with natural gas.
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<br />5.2. Excess Thermal Energy at the Ice Arena and Banquet Hall
<br />The following graph illustrates the amount of thermal energy dissipated by the
<br />refrigeration plant in the ice Arena compared to the amount of thermal energy required
<br />for space heating and hot water in the Ice Arena 1 Banquet Hall facility.
<br />Geo-Xergy Systems Page 15 of 33
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