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OPEN LOOP GEOTHERMAL SYSTEMS

OPEN LOOP GEOTHERMAL SYSTEMS. Gary Dannemiller CPG, PG, Hydrologist. TRITERRA.

Albert_Lan
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OPEN LOOP GEOTHERMAL SYSTEMS

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  1. OPEN LOOP GEOTHERMAL SYSTEMS Gary Dannemiller CPG, PG, Hydrologist

  2. TRITERRA • A major cost in the installation of a geothermal system is the ground source heat exchange system. There are three major types used in Michigan, closed horizontal and vertical loops and open loop (well). Costs can vary from 50% to 100% between each method. • Triterra specializes in open loop systems. Open loop systems require the services of experienced hydrologists and geochemists due to the complex requirements.

  3. Requirements for a Feasibility Evaluation Open Loop Geothermal System • Determine amount of groundwater required for operation. • Perform literature search of available well logs, area hydrologic investigations , permit requirements and groundwater quality reports. • Perform preliminary evaluation of alternatives for discharge water disposal. • Prepare a feasibility report with the likelihood of an open loop system operating, discharge alternatives, potential water quality issues and cost estimates.

  4. Detailed Components ofFeasibility Evaluation • Heat/Cooling Load • Obtain thermal loads from architect and assign an estimated production rate of 2 gpm per ton of requirement. • Consider different heat loads from changes in construction and evaluate construction cost changes to costs in changing geothermal capacity requirements.

  5. Detailed Components ofFeasibility Evaluation • Literature Search • MDEQ well log files • USGS hydrologic investigations • University research papers • County Health Department files • MDEQ Leaking Underground Storage Tank files (Part 213) • MDEQ hazardous materials (Part 201) • EDR radius map for sites of environmental contamination • Evaluate pumping rate allowable through MDEQ Groundwater Assessment Tool • Permit requirements

  6. Detailed Components ofFeasibility Evaluation • Discharge Alternatives • Land surface discharge • NPDES permit for flow and temperature • Storm sewer discharge available capacity • Wetland/lake discharge • Groundwater discharge • Water garden • Infiltration gallery • Injection back into the aquifer • If above 300,000 BTU/Hr need groundwater discharge permit

  7. Triterra Services for ConstructionOpen Loop • Prepare bid specifications for installation of production well and two observation wells. • If there are nearby areas of contamination , address the potential impact by installing monitoring wells in the flow path of the contamination between production well and contamination site. • Provide well construction management oversight. • Evaluate production well screen efficiency if applicable, water quality, area of impact, safe yield, aquifer hydraulic characteristics by conducting a step and aquifer stress test.

  8. Triterra Services for ConstructionOpen Loop • Prepare bid specifications • Specify depth, diameter, well development, type of grout, casing, screen type if applicable, type of pump for installation of production well and two observation wells. • If preliminary feasibility study indicates area contamination of concern, design a monitoring plan and number of monitoring wells that would be used during the aquifer stress test to evaluate if there is a problem.

  9. Triterra Services for ConstructionOpen Loop • Construction Management • Provide construction management oversight of well construction. • Monitor construction of well, annular space sealing and aquifer drilling to obtain proper depth to place casing, screen length and slot size if used and depth of open hole in the aquifer.

  10. Triterra Services for ConstructionOpen Loop • Well Testing • Provide construction management oversight of well construction. • Monitor construction of well, annular space sealing and aquifer drilling to obtain proper placing casing, screen length and slot size if used and depth of open hole. • Design and perform aquifer step test (8 hour) to obtain pumping rate to operate aquifer stress test, obtain preliminary aquifer characteristics and evaluate well screen efficiency if present.

  11. Triterra Services for ConstructionOpen Loop • Well Testing (Continued) • Perform aquifer stress test (24 hour confined aquifer or 72 hour unconfined aquifer). • Record water level changes in production and monitoring wells every minute by use of well water level recorders. • Use groundwater model AQTESOLV to interpret groundwater characteristics such as hydraulic conductivity, storativity and transmissivity. • Project 100 day draw down with continuous pumping

  12. Vertical Open Loop – Well - Lake Discharge

  13. Cross-section of an Open Loop System with an Injection Well

  14. Aquifer Stress Test

  15. Aquifer Stress Test Analysis

  16. Glacial and Bedrock Geology of MichiganLower Penninsula

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