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IGSHPA Technical Conference & Expo
Baltimore, Maryland
Direct Insertion Ground Loop
Heat Exchanger
Charles Cauchy
October 15 - 16, 2014
Slide 1 of 24
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. Conclusions
10.Acknowledgements
11.Closing
Slide 2 of 24
The Challenge
• Biggest barrier to
greater geothermal
heat pump use
• High cost
• Large area
• Large & expensive
equipment
Slide 3 of 24
The Solution
EarthSpar™
•
•
•
•
•
50% Cost Reduction
Low landscape disruption
Gets into small areas
Fast installation
High thermal performance
Patent Pending
Slide 4 of 24
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
Slide 5 of 24
Potential Benefits
The Direct Insertion Ground Loop Heat Exchanger
addresses 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 understructure installation or radial center point headering
Slide 6 of 24
The Technology
Core Concept – Part A
Water Jets/Metal Driving Tip
•
•
•
•
•
•
Loosening soil
Lubricating insertion
Dislodging rocks
Displacement
Hard soil erosion
Deflection
EarthSpar™
Slide 7 of 24
The Technology
Core Concept – Part B
Up Pipe Flow
Concentric Tube Design
• Single Tube Heat Exchanger
• With same flow rate achieve
laminar flow in down-flow
• Turbulent flow in up-flow
Down Pipe Flow
• Improved thermal performance
Slide 8 of 24
The Technology
Pressure Drop in 20ft. EarthSpar™
Coaxial Heat Exchanger
Same cross-sectional area
Slide 9 of 24
The Technology
Pressure Drop in 20ft. EarthSpar™
Coaxial Heat Exchanger
Slide 10 of 24
The Technology
Core Concept – Part C
Insertion Platform
Slide 11 of 24
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 on
targets, will be increased)
• Extraction of heat exchanger – straightforward and rapid
Slide 12 of 24
Thermal Testing
20’ EarthSpar™ 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°FΔT
• Wireless data acquisition
Slide 13 of 24
80
3:30:59 PM
4:06:00 PM
4:41:00 PM
5:16:01 PM
6:37:23 PM
7:12:24 PM
8:02:36 PM
8:37:37 PM
9:12:37 PM
9:08:57 AM
9:43:58 AM
10:18:58 AM
10:53:59 AM
11:28:59 AM
12:04:00 PM
12:39:00 PM
1:25:11 PM
2:00:12 PM
2:35:12 PM
3:10:13 PM
3:45:13 PM
4:20:14 PM
5:01:00 PM
5:36:01 PM
6:11:01 PM
8:47:12 PM
8:06:22 AM
8:44:41 AM
Temperature
Thermal Testing
Test Data
120
100
y = 2.2366ln(x) + 80.241
Slope of Ave. Temp.
60
40
20
0
IN
OUT
Ave. Δ T
Ambient
Linear (IN)
Linear (OUT)
Log. (Ave. Δ T)
Linear (Ambient)
Time ~ 41.5 Hours
After 5 Hours Stabilization
Slide 14 of 24
Thermal Testing
Thermal conductivity: Line Source Method
𝑘 = 3.412 ×
𝑃
4𝜋𝐿 × 𝑆𝑙𝑜𝑝𝑒
356𝑊
𝑘 = 3.412 × 4𝜋17.8𝑓𝑡 ×2.2366 = 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
Slide 15 of 24
Performance Benefit
Effect of Ground Loop Heat Exchanger Thermal
Conductivity on Loop Length
1000
900
0.96
800
y = 850.06x-0.473
Loop Length ft
700
1.44
2.00
600
500
2.24 EarthSpar
400
300
200
100
0
0
0.5
1
1.5
2
2.5
3
3.5
Thermal k Btu/hr-ft-F
Slide 16 of 24
System Flexibility
• Angular insertions
• Under structures
• Radial loop field
• Extraction - straightforward
• Shallow water wells
• Under structure races for
utilities, communications
lines, water lines
Slide 17of 24
Technology Review
•
•
•
•
•
•
•
•
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
Slide 18 of 24
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
Slide 19 of 24
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
Pipe
$1,252
$2,240
Connection Pipe, Fittings
$ 400
$1,000
Completion labor, etc.
$1,100
$1,400
Total
Insertion labor
$11,852 $6,040
Slide 20 of 24
Method Comparisons
EarthSpar™
Drilling
Earth Moving
Other
Low Cost
Landscape
Preservation
Limited
Access
High
Performance
Existing Loop
Paradigms
Slide21 of 24
Conclusions
1.
2.
3.
4.
5.
6.
7.
8.
9.
The EarthSpar™ concept is a viable technology
Core concepts were proven to work to drive pipe, displace soils
and function even with obstructions (rocks)
Insertion times (> 2 ft/min) allow for rapid placement of GSHP
ground loops
High thermal performance may lead to shorter lengths of heat
sink in the ground than with conventional designs
Small, mobile insertion equipment allows for ground loops to be
placed in space restrained areas
Capital costs associated with ground loops (bore drilling and
large horizontal field processes) are greatly reduced
Project goals were met (rapid insertion & thermal testing)
Can reduce ground loop installation cost by 50%
Will expand GSHP market in residential & small commercial
Slide 22 of 24
Acknowledgements
Special thanks
to 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
Slide 23 of 24
Charles Cauchy
[email protected]
231-633-1702
www.promethientgeo.com
Slide 24 of 24