Geothermal Heat Pump Presentation

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GeoExchange Technologies Utility Geothermal
Working Group Webcast April 18, 2006
Chiloquin Community Center 16 vertical
boreholes water-water heat pump providing
radiant floor heating and cooling

Andrew Chiasson Geo-Heat Center Oregon Institute
of Technology
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Presentation Outline
Slide 2

• 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.)

Detroit, MI
Australia
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OverviewBrief Historical Summary
Slide 3

• 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)

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OverviewWhat do GHP systems provide?
Slide 4

• Heating
• Cooling
• Hot water
• Humidity control
• Ice making

Residential Heat Pump

• but also
• Energy efficiency
• Decreased maintenance
• Decreased space needs
• Low operating costs
• Comfort air quality

Lowell, MA

• No outdoor equipment (no noise or outdoor
  maintenance)
• For utilities reduced peak electrical loads in
  summer, additional electrical use in winter

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Components of GHP Systems
Slide 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

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ComponentsTypes of Earth Connection
Slide 6

• Vertical (GCHP)
• Rocky ground
• More expensive
• Little land used
• High efficiency per unit length

• Horizontal (GCHP)
• Most land used
• Less expensive, easier to install
• Ground temperature varies

• Groundwater (GWHP)
• AquiferInjection
• Lower cost than closed-loop
• Regulations
• Possible fouling/scaling concerns

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ComponentsTypes of Earth Connection
Slide 7

• Surface Water (SWHP)
• Low cost
• Integrate into landscape
• Different heat transfer processes (evaporation,
  thermal storage)

• Standing Column Well (SCW)
• Hard rock geology with high quality groundwater
• Low ft/ton and very little land area
• Open closed-loop characteristics
• Groundwater regulations

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Design Considerations
Slide 8
Undisturbed Earth Temperature
Average Thermal Conductivity Heat Capacity
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Technology ImprovementsHeat Pump Equipment
Slide 9

• 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

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Technology ImprovementsThermal Conductivity
Testing
Slide 10

• 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

First generation unit (trailer)
Compact testing units
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Technology ImprovementsBorehole Heat Exchanger
Design
Slide 11

• Goal is to lower the borehole thermal resistance

Geo-Clip Spacers
Double U-tubes
Thermally-enhanced grouts improved grout
pumps (Bentonite sand mixtures)
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Technology ImprovementsPond Heat Exchanger
Design
Slide 12
Copper Pond Loop Experiment (OSU)
Geo-Lake Plate
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Technology ImprovementsStanding Column Well
Design
Slide 13

• 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

500 2000 ft
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Technology ImprovementsHybrid Systems
Slide 14

• 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?)

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Hybrid SystemsShallow (or surface) Heat
Rejecters
Slide 15

• 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

Photo credit Marvin Smith, OSU
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Hybrid SystemsSolar Applications
Slide 16
University of Wyoming Test Site

• Uses some old ideas of borehole heat storage with
  some new concepts

4 single U-tube vertical borehole heat
exchangers (200 ft deep)
Source E. Kjellsson, IEA Heat Pump Newsletter,
Vol. 23, No. 1
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Technology ImprovementsSimulation of Complex
Systems
Slide 17

• 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

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New PerspectivesLoads Integration with
GeoExchange
Slide 18

• Example of an ice arena

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New PerspectivesCommunity Loops
Slide 19
Lake Las Vegas Resort Closed-Loop in Lake

• 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

Sewer Heat Exchanger Rabtherm Corp.
Groundwater Loop, B.C. Central production wells
with infiltration galleries at each home
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Conclusions
Slide 20

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