11-04-2024 Special JDA Agenda Packet

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17 TGRS In-Ground HE Geothermal Wellfields Cost per Ton of Cooling $/Ton $2,420 $5,000 $15,000 Cost per MMBtu/hr of Heating $/MMBtu/hr $200,000 $830,000 $1,250,000 Table 5. Estimated probable cost per unit of production capacity Integrating heat transfer with the groundwater remediation process offers the lowest installation cost per unit of energy, it could reduce the RCC district energy production source cost by over $7 million. The groundwater remediation system would eliminate the requirement for 10 in-ground heat exchangers or 365 geothermal wells (approximately 3.5 acres of wellfield). However, there is sufficient capacity for district energy from other solutions if it is not possible to use the TGRS. Assuming the next available lowest-cost energy solution is the in-ground heat exchangers, the impact on the total cost for production capacity is shown in Table 6. Without TGRS Connection With TGRS Connection RCC Full District Energy MM$ $48.9 $41.7 Town Center District Energy MM$ $26.0 $19.4 Table 6. Cost comparison of the district energy system using the groundwater remediation system to the energy system or not 4.3. District Energy System Distribution The community-wide district energy distribution system would operate as a tepid water loop, enabling buildings to both reject and extract heat. This system would be closed-loop and comprise supply and return piping in the Town Center and Outlot A and single-pipe loops in the residential neighborhoods. The water in this closed-loop tepid water system will originally come from the city water system, not the aquifer. Constructed of high-density polyethylene (HDPE), the distribution piping is estimated to range in diameter from 2 to 16 inches, except for service laterals. To serve every building on the RCC site a conceptual pipe route is shown in Figure 9, the route includes over 45,000 trench feet (8.5 miles) of piping. The estimated cost to install the piping network is $34.3 million. One strategy to reduce distribution costs involves implementing a single-loop main pipe instead of the traditional supply and return mains. Each building connection would require a supply and return service pipe equipped with a pump to circulate water. The water would be drawn from the main loop, passed through a heat pump, and then returned to the loop. This single-pipe loop approach was assumed for the residential neighborhoods, which reduces installation costs. However, during periods of high demand, the loop may trend warmer or colder for buildings located on the far end of the loop, slightly impacting their equipment efficiency.