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GeoExchange Technologies Utility Geothermal Working Group Webcast April 18, 2006

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GeoExchange Technologies Utility Geothermal Working Group Webcast April 18, 2006

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    2. Presentation Outline Overview of geothermal heat pump (GeoExchange) systems Brief history System components Areas of recent technology improvements Heat pump equipment Thermal conductivity testing Borehole heat exchanger design Hybrid systems Computer-aided simulation methods New perspectives Loads integration Community loops Sustainable buildings (LEEDS, etc.)

    3. Overview: Brief Historical Summary Early days Open-loop systems using groundwater wells or surface water First commercial applications beginning in 1940s 1970s - early 1980s Beginnings of R & D of closed loop systems (simultaneously in Sweden and U.S.) Several 1980s failures of air-source heat pumps gave all heat pumps a bad reputation Late 1980s - 2000 Emergence and slow growth of GHP market Continuing R & D; development of design tools and manuals Certifications for designers through various organizations (IGSHPA, ASHRAE, AEE)

    4. Heating Cooling Hot water Humidity control Ice making Overview: What do GHP systems provide?

    5. Earth connection Closed-loop (vertical, horizontal, lake or pond) Open-loop Water-source heat pump Vapor-compression cycle Interior heating/ cooling distribution subsystem Conventional ductwork Radiant system Components of GHP Systems

    6. Components: Types of Earth Connection

    7. Components: Types of Earth Connection

    8. Design Considerations

    9. Technology Improvements: Heat Pump Equipment Numerous small improvements over past 10 years Variable-speed fans Microprocessor controls (allows easier troubleshooting) Improved water-refrigerant coils New refrigerants (non-ozone depleting) Low-temperature heat pumps for refrigeration applications

    10. Technology Improvements: Thermal Conductivity Testing ASHRAE-sponsored research project in (1999-2000) compiled field-test methods and data analysis methods Testing time depends on borehole design 40-hour test is recommended Probably not cost-effective on small commercial and residential projects

    11. Technology Improvements: Borehole Heat Exchanger Design Goal is to lower the borehole thermal resistance

    12. Technology Improvements: Pond Heat Exchanger Design

    13. Technology Improvements: Standing Column Well Design ASHRAE-sponsored research project (2000-2002) Identified several hundreds of installations, mostly in New England and Eastern Canada (areas of hard rock with good groundwater quality) Good for locations with limited land area Detailed computer modelling identified the most important parameters as: Bleed strategy Borehole depth Rock thermal & hydraulic properties Borehole diameter Water table depth

    14. Technology Improvements: Hybrid Systems Current ASHRAE-sponsored research project just underway Motivation is due to necessity of large loops in applications with unbalanced annual loads (due to thermal storage effects of soils/rocks) A supplemental piece of equipment handles some portion of the load: Boiler Solar collectors Cooling tower Pond or swimming pool Shallow heat rejecters What is the optimal system design and control (time of day? year?)

    15. Hybrid Systems: Shallow (or surface) Heat Rejecters SHRs (shallow or surface) heat rejecters Shallow horizontal loops are used to thermally “unload” vertical borehole field in winter or during cool nights Additional benefit of slab warming and snow melt assistance Could also incorporate turf systems or storm water ponds

    16. Hybrid Systems: Solar Applications Uses some old ideas of borehole heat storage with some new concepts

    17. Technology Improvements: Simulation of Complex Systems Development of many component-based, modular computer models Driven by hourly weather data Allows optimization of designs However, can be cumbersome and not available to everybody Working toward making these more usable

    18. New Perspectives: Loads Integration with GeoExchange Example of an ice arena

    19. New Perspectives: Community Loops Not a new idea, but New ideas of heat exchange Sewers (gray, black water) Thermal storage Several ownership scenarios Home-owner associations Third-party Developer-owned Utility-owned Developers are the key

    20. Conclusions GeoExchange technologies have evolved considerably since their beginnings Most recent efforts in making GeoExchange more economic include applications that have balanced or shared loads => these applications are almost limited by our imagination Hybrid systems and integrated load systems can be tricky to design, but we’re currently working toward developing streamlined design tools GX playing increasingly larger role in sustainable buildings and in reduction in CO2 emissions

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