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Geothermal Heat Pump SystemsGeothermal Heat Pump SystemsBeing Green by using the GroundBeing Green by using the Ground

Presented by:Warren (Trey) Austin,Warren (Trey) Austin,

PE, CEM, CGD, LEEDPE, CEM, CGD, LEED--AP AP GeoGeo--Energy Services, LLCEnergy Services, LLC

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What is the difference between geothermal, ground-source or GeoExchange?Where does the energy come from?What makes ground-source heat pumps energy efficient?How does it heat/cool?How much does it cost?What are the O&M costs?Are there rebates or grants?What are the applications?

Most Often Asked QuestionsMost Often Asked Questions

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Geothermal 101Geothermal 101Terminology

GeoExchange- General term that groups all aspects of the technology and industry together

Ground Source Heat Pump- A heat pump the uses the earth or ground as a source for heat of absorption or heat of rejection

COP- Coefficient of Performance; Rating for Heating Mode- DHW Heating Only for our case

EER- Energy Efficiency Ratio; Rating for Cooling Mode

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Geothermal 101Geothermal 101Terminology Continued

BoreholeHDPEGrout

Ground Thermal Conductivity

dtdTkq ground=&

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Answers to Common QuestionsAnswers to Common QuestionsWhat is the difference between Geothermal and Ground-Source?

Geothermal is the typically associated with a direct-use application of high temperature ground water- ACTIVEGround-source is a term that means you are using the near constant temperature of the earth as a heat sink or heat source- PASSIVE

Where Does the Energy Come From?Two Sources

• The natural passive geothermal gradient• The energy absorbed by the Sun!

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The earth is like a solar battery absorbing nearly half of the sun’s energy. The ground stays a relatively constant

temperature through the seasons.

45% absorbed by

ground

Space

Atmosphere

Earth

U.S. Dept. of Energy

Passive geothermal gradient

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Answers to QuestionsAnswers to QuestionsWhat makes ground-source heat pumps energy efficient?

Ground-coupled heat pumps take advantage of 2 ½ to 1 gain in energy output to energy input with the characteristics of heat transfer to fluid in the loop with the ground.

How does it Cool?Refrigeration circuit with phase changes moves energy from a “hot” source to a “cold” source even at high fluid temperatures (>95°F).

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Ground Loop Temperature ProfileGround Loop Temperature Profile

0

10

20

30

40

50

60

70

80

90

100

1 11 21 31 41 51 61 71 81 91 101 111 121 131 141 151 161 171 181 191 201 211 221 231Time (months)

Tem

pera

ture

(F)

TgroundTfluidTheatTcoolTideal

Tfluid = 9600’

Tideal = 32,960’

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30%-60% Lower Operating / Energy Cost40%-70% reduction in Green House Emissions Longer life span Greater ComfortLess Maintenance, Simplified ControlsBetter Aesthetics (no exposed outdoor equipment)LEED/Green Building solutions

Benefits of GSHP SystemBenefits of GSHP System

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Internal Component of Internal Component of GeoExchange SystemsGeoExchange Systems

CV Air UnitsHorizontal HPVertical HPConsole HPRooftop HP

Hydronic UnitsWW HP

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Cost and PaybacksCost and PaybacksInstallation cost ranges $10.00 to $20.00 / ft2

Operating costs $0.35 to $0.85 /ft2-yr Paybacks can be immediate to 5 years

Average: 5-8 yearsSome systems can be 8-12 years

Rebates Depend on local utilities

Tax CreditsFederal and some State

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Project ConsiderationsProject ConsiderationsKnow the Design Parameters

Space Heating/Cooling• Air Distribution• Radiant Floor Heating• Hot Water/Chilled Water Integrated Systems

Other Auxiliary Loads• DHW• Snowmelt- Heat Rejection• Refrigeration

Thermal Conductivity Test

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Project ConsiderationsProject ConsiderationsLoop Fields

Performance indifferent when properly designed at the same EWTsEfficiency of equipment directly correlated to EWT Pond/Lake Loops or Plates

• Be cautious about Icing or OverheatingHorizontal Loops

• Sizing loop must account for frost depths, surface snow, seasonal amplitude temperature changes

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Loop Fields (continued)Vertical Boreholes

• Least site restrictive due to greater depths for heat transfer

• Accounts for majority of all installation (>80%)• Typical 2” and 3” header lines

2” = 4-7 boreholes per header3” = 6-12 boreholes per header

• Generally like to be the lowest utility

Project ConsiderationsProject Considerations

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Loop Fields (continued)Hybrid Configuration

• Combine any of three traditional loop field designs to help reduce cost

• Combine with condensing boiler/solar heating technologies in heating load dominant situations

• Combine with fluid coolers/cooling towers in cooling load dominant situations

• Due to increasing use, further research is underway

Project ConsiderationsProject Considerations

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Loop Fields (continued)In certain situations, a retrofit may be site prohibitive.Combine energy efficiency improvementsPrevious energy efficiency improvements may PROHIBIT a feasible retrofit Consider electrical service upgrades

Project ConsiderationsProject Considerations

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Heat Rejection/Absorption SynergiesHeat Rejection/Absorption SynergiesSpace Cooling

Refrigeration Rejection

Hot WaterHeating Load

Shallow HeatRejection Slab

GreywaterReclaim

Fluid Cooler

Rainwater Reclaim

Ground LoopHeat

Exchanger

Space Heating

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Vertical Loop Installation EquipmentVertical Loop Installation Equipment

FusionEquipment

FlushingTrailer

Grout

Pipe

DrillRig

VerticalGround

Loop

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Vertical Loop FieldVertical Loop Field

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VaultVault

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Horizontal Slinky (Pit) LoopHorizontal Slinky (Pit) Loop

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Pond/Lake LoopPond/Lake Loop

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Pond LoopPond Loop-- Plate Heat ExchangerPlate Heat Exchanger

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The The CxCx PerspectivePerspectiveInternal

No Different that any other HVAC system• Piping

½” Insulation only for condensationHDPE pipe for interior as potential a cost saving measure

• DuctworkFlex duct collars to isolate vibration

• Circulating PumpsPrimary/SecondaryLead/LagZone Pumping/Individual

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The The CxCx PerspectivePerspectiveInternal (continued)

Equipment• Location important for sufficient access

Filter ReplacementFan Motor/HousingCompressor MaintenanceMfr’s Recommended Clearance- Specific Areas

• P/T Ports at Unit- can be integrated with hose kitsEquipment Cx- Flow and Capacity

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The The CxCx PerspectivePerspectiveInternal (continued)

Equipment• Air

PSC- Fixed Speeds (L/M/H)ECM-Variable Speed (Dip Switch)

Conjoined with 2-speed compressors

Controls• Basic T-stat operation• DDC with integrated internal/external controllers

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The The CxCx PerspectivePerspectiveInternal (continued)

Space Temperature Control• Standard heating and cooling setpoints (5 diff.)• Single setpoint with autochangeover

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The The CxCx PerspectivePerspectiveExternal

P/T Ports• Supply and Return Header lines

Pipe• Fusion Joints

Butt FusionSocket FusionElectro Fusion

• Reverse Return

Properly Flush and Purged

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The The CxCx PerspectivePerspectiveExternal (continued)

Grout• Properly mixed

Periodic samples- independently tested by mfr (free service)

• Grouted from bottom to top• No native backfill or pea gravel (by preference)

Proper balanced headers at manifoldProper tracer wire/metallic tape

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The Good, The Bad, The UglyThe Good, The Bad, The Ugly

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Developing the Developing the ““SolutionSolution””Optimization of Energy Performance must consider:

Utility RatesEvaluation of ALL System interactions

Select a GSHP for the right applicationEnergy performance criteria can influence decisions that may be different for each applicationBecome cognizant and aware of real issues so that informed decisions can be madeUnderstand Peak Load Durations based on system configuration

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International Ground Source Heat Pump Associationwww.igshpa.okstate.edu

Geothermal Heat Pump Consortiumwww.geoexchange.org

ASHRAE:Commissioning, Preventive Maintenance, and Troubleshooting Guide for Commercial Ground-Source Heat Pump Systems –ASHRAE Publication

Operating Experiences with Commercial Ground-Source Heat Pump Systems- 1998 ASHRAE Publication

Comparative Analysis of Life-Cycle Costs of Geothermal Heat Pumps and Three Conventional HVAC Systems- 2000 ASHRAE Transactions

Internet and Literature ResourcesInternet and Literature Resources

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Questions?Questions?