10 16 2014 1030 charles cauchy direct insertion ground loop heat exchanger

8/18/2019 10 16 2014 1030 Charles Cauchy Direct Insertion Ground Loop Heat Exchanger

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Direct Insertion Ground Loop

Heat Exchanger

Charles Cauchy

October 15 - 16, 2014

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IGSHPA Technical Conference & Expo

Baltimore, Maryland


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Outline

1. Challenge – Solution

2. US DOE Program Goals

3. Technology

4. Thermal Test Results

5. Technology Review

6. Areas of Use

7. Example System Costing

8. Method Comparisons

9. Conclusions10.Acknowledgements

11.Closing

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The Challenge

• Biggest barrier to

greater geothermal

heat pump use

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• High cost• Large area

• Large & expensive

equipment


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Development Overview

Awarded US Dept. of Energy Grant - 2013

GOAL of Program:

To develop a ground loop heat exchanger that can be:

• Expediently inserted into the earth• Via the use of man-portable equipment• Resulting in low cost, space efficient ground loops for

ground source heat pumps• Thermally testing the heat exchanger

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The Direct Insertion Ground Loop Heat Exchangeraddresses key barriers to wider GSHP adoption by:

• Significantly reducing high installation costs for ground loops

• Reducing space requirements for ground coupling (slinky

field or large drilling equipment in densely built areas)

• Greatly reducing ground cover disruption and providing a

flexible grid structure for placement around obstacles

• Allows for angular ground loop placement enhancing under-

structure installation or radial center point headering

Potential Benefits

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The Technology

EarthSpar ™

Core Concept – Part A

Water Jets/Metal Driving Tip

• Loosening soil

• Lubricating insertion

• Dislodging rocks

• Displacement

• Hard soil erosion

• Deflection

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The Technology

Core Concept – Part B

Concentric Tube DesignUp Pipe Flow

Down Pipe Flow

• Single Tube Heat Exchanger

• With same flow rate achieve

laminar flow in down-flow

• Turbulent flow in up-flow

• Improved thermal performance

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The Technology

Pressure Drop in 20ft. EarthSpar ™

Coaxial Heat Exchanger

Same cross-sectional area

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The Technology

Pressure Drop in 20ft. EarthSpar ™

Coaxial Heat Exchanger

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The Technology

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Core Concept – Part C

Insertion Platform


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The Technology

Heat Exchanger Insertion

• Insertion into varying soil types

• Sand, sandy loam

• Gravel, cobble

• Clay

• Subsurface boulder field (Insertion halted)

• Insertion speed ~ 2 – 4 ft/min

• Insertion for 24, 30ft heat exchangers ~ 6 hours at 2 ft/min

[700 ft] 3 hours at 4 ft/min

(total insertion time, including equipment placement ontargets, will be increased)

• Extraction of heat exchanger – straightforward and rapid

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Thermal Testing

• ASHRAE 1118-TRP

• Inline water heating device

• Precision Watt meter – energy-in

• Input power control

• Thermocouples – in-flow &

out-flow temperatures

• Flow meter – in-line

• ~ 10°F ΔT• Wireless data acquisition

20’ EarthSpar ™ Testing

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y = 2.2366ln(x) + 80.241

Slope of Ave. Temp.

0

20

40

60

80

100

120

3 : 3 0 : 5 9 P M

4 : 0 6 : 0 0 P M

4 : 4 1 : 0 0 P M

5 : 1 6 : 0 1 P M

6 : 3 7 : 2 3 P M

7 : 1 2 : 2 4 P M

8 : 0 2 : 3 6 P M

8 : 3 7 : 3 7 P M

9 : 1 2 : 3 7 P M

9 : 0 8 : 5 7 A M

9 : 4 3 : 5 8 A M

1 0 : 1 8 : 5 8 A M

1 0 : 5 3 : 5 9 A M

1 1 : 2 8 : 5 9 A M

1 2 : 0 4 : 0 0 P M

1 2 : 3 9 : 0 0 P M

1 : 2 5 : 1 1 P M

2 : 0 0 : 1 2 P M

2 : 3 5 : 1 2 P M

3 : 1 0 : 1 3 P M

3 : 4 5 : 1 3 P M

4 : 2 0 : 1 4 P M

5 : 0 1 : 0 0 P M

5 : 3 6 : 0 1 P M

6 : 1 1 : 0 1 P M

8 : 4 7 : 1 2 P M

8 : 0 6 : 2 2 A M

8 : 4 4 : 4 1 A M

T e m p e r a t u r e

Time ~ 41.5 Hours

After 5 Hours Stabilization

IN

OUT

Ave. Δ T

Ambient

Linear (IN)

Linear (OUT)

Log. (Ave. Δ T)

Linear (Ambient)

Thermal Testing

Test Data

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Thermal Testing

Thermal conductivity: Line Source Method

= 3.412 ×

4 ×

= 3.412 ×56

7.8 ×.66 = 2.249 Btu/hr-ft-°F

• 20W/ft heat rate

• 17.8 ft of tested length – heat exchanger

• ~ 10°F ΔT (heated IN – earth cooled OUT)• Thermal insulation between down-flow & up-flow

concentric tubes for 67% of length

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0.96

1.44

2.00

2.24 EarthSpar

y = 850.06x-0.473

0

100

200

300

400

500

600

700

800

900

1000

0 0.5 1 1.5 2 2.5 3 3.5

L o o p L e n g t h f t

Thermal k Btu/hr-ft-F

Effect of Ground Loop Heat Exchanger Thermal

Conductivity on Loop Length

Performance Benefit

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System Flexibility

• Angular insertions

• Under structures

• Radial loop field• Extraction - straightforward

• Shallow water wells

• Under structure races for

utilities, communicationslines, water lines

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• Water-jet technology

• Soil displacement/insertion

• Tangential obstruction dodging• One-step process

• Concentric - High thermal performance

• Agile insertion platform – tight areas

• Angular insertion• Easily extract heat exchanger

Technology Review

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Areas of Use

Where Drilling or Trenching May Be Superior

• Where bedrock is close to the surface

• Areas/soils with closely spaced large rocks

• Large commercial/industrial/institutional systems

• Single source ground loop/non-distributed• Excavation already planned (i.e.. Parking lot)

• Capital equipment (i.e.. Drilling rigs) on-site and can be

amortized over many borings

• Limited space (tons/ft2) – drilling excels

EarthSpar ™ will not replace existing ground loop methodologies

EarthSpar ™ will be strong adjunct methodology in many applications

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Cost Advantage

Estimated Ground Loop Cost Comparison

Standard Ground Loop $ vs. DIGLHE $4 ton example (700’ Vertical)

Boreholes DIGLHE

Drilling w/grout $9,100 $1,400 Insertion labor

Pipe $1,252 $2,240

Connection Pipe, Fittings $ 400 $1,000

Completion labor, etc. $1,100 $1,400

Total $11,852 $6,040

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Method Comparisons

Low Cost

LandscapePreservation

Limited

Access

High

Performance

Drilling OtherEarth Moving

Existing Loop

Paradigms

EarthSpar ™

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1. The EarthSpar ™ concept is a viable technology2. Core concepts were proven to work to drive pipe, displace soils

and function even with obstructions (rocks)3. Insertion times (> 2 ft/min) allow for rapid placement of GSHP

ground loops

4. High thermal performance may lead to shorter lengths of heatsink in the ground than with conventional designs

5. Small, mobile insertion equipment allows for ground loops to beplaced in space restrained areas

6. Capital costs associated with ground loops (bore drilling andlarge horizontal field processes) are greatly reduced

7. Project goals were met (rapid insertion & thermal testing)8. Can reduce ground loop installation cost by 50%9. Will expand GSHP market in residential & small commercial

Conclusions

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Special thanksto the U.S. Department of Energy and Bahman

Hebibzadeh (DOE Program Manager)

for supporting the development of the EarthSpar ™Direct Insertion Ground Loop Heat Exchanger

&

Rex Ambs – Geofurnace LLC

&

IGSHPA

Acknowledgements

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Charles Cauchy

[email protected]

231-633-1702

www.promethientgeo.com

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mailto:[email protected]:[email protected]

10 16 2014 1030 charles cauchy direct insertion ground loop heat exchanger

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