11-04-2024 Special JDA Agenda Packet

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13 4.2.2. CLOSED-LOOP GEOTHERMAL WELLFIELDS Closed-loop geothermal wellfields coupled with a tepid water district energy system utilize the stable ground temperature (approximately 55°F) for heating and cooling. A network of closed-loop wells is drilled into the ground to circulate water, which acts as a heat transfer fluid. This water would circulate through a closed-loop system, transferring heat to or from the ground as needed. In winter, the ground's warmth is extracted and distributed to buildings via the tepid water district energy system network. Conversely, in summer, heat is transferred from buildings to the ground for cooling. Figure 5. Closed-loop geothermal well Geothermal wellfields can be installed beneath parking lots, athletic fields, and most green spaces. The wells are fully concealed, allowing uninterrupted use of the surface area above. Each well typically costs around $30,000, but costs can vary significantly depending on soil conditions and well depth. Each well can produce 1 to 3 tons of cooling or heating capacity. At an average capacity of 2 tons per well, the cost for geothermal is $15,000 per ton, or approximately $1.25 million per MMBtu/hr. To serve the entire RCC development, approximately 2,850 wells would be required, occupying 27.5 acres of land for geothermal wellfields, at a total estimated cost of $86 million. Figure 6 illustrates potential locations for well fields (shown in orange), which when combined, would exceed the high-performance building heating and cooling demand for RCC. The district energy system allows the wellfields to be split up and installed in various locations along the distribution loop. This provides system redundancy and can allow for reduced distribution pipe sizes. A district energy network may require 20% to 30% less wells when compared to each building installing their own wells, due to system load diversity.