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Geothermal Heat Pump Presentation

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GeoExchange Technologies. Utility Geothermal Working Group Webcast. April 18, 2006 ... Low ft/ton and very little land area. Open & closed-loop characteristics ... – PowerPoint PPT presentation

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Title: Geothermal Heat Pump Presentation


1

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
2
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
3
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)

4
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

5
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

3
2
1
6
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

7
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

8
Design Considerations
Slide 8
Undisturbed Earth Temperature
Average Thermal Conductivity Heat Capacity
9
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

10
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
11
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)
12
Technology ImprovementsPond Heat Exchanger
Design
Slide 12
Copper Pond Loop Experiment (OSU)
Geo-Lake Plate
13
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
14
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?)

15
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
16
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
17
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

18
New PerspectivesLoads Integration with
GeoExchange
Slide 18
  • Example of an ice arena

19
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
20
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
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