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Kenneth Von Bank, PE, CCPMechanical EngineerSustainable Engineering Group LLC
Commissioning Geothermal Systems
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Learning Objectives
1. Gain a better understanding of the challenges of geothermalsystem design, installation, and operation.
2. Demonstrate the ability to incorporate the knowledge ofgeothermal systems into all phases of the commissioningprocess.
AIA Quality Assurance
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Assumptions
Geothermal system has been shown tobe the best fit for the project through aLife Cycle Cost Analysis or similar
Geothermal feasibility study has beenperformed
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Energy From the Earth/Sun
Earth = solar battery
Absorbs nearly halfof the suns energy.
The ground stays arelatively constanttemperature
Warm heat source inwinter
Cool heat sink in
summer
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The earth is like a solar battery absorbing nearly half of the suns energy.
The ground stays a relatively constant temperature through the seasons,
providing a warm source in winter & a cool heat sink in summer.
4% absorbedby clouds.
17% reflected
by clouds.
6% reflected
by surface.
19% absorbed by
water vapor, dust
46% absorbed bythe ground
Outer SpaceOuter SpaceOuter SpaceOuter Space
AtmosphereAtmosphereAtmosphereAtmosphere
EarthEarthEarthEarth
100%100%100%100%
Nearly of thesuns energy is
absorbed by earth
5
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Ground-Source Heat Pumps
GSHP
A term applied to a variety of system
components that use the ground,groundwater, or surface water as a heatsource and sink.
Also Known As: Ground-Coupled Heat Pumps (GCHP)
Ground-Water Heat Pumps (GWHP)
Surface Water Heat Pumps (SWHP)
Direct Expansion (DX) GCHP
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Ground Coupled Heat Pumps (GCHP)
Closed-loop ground-source
heat pumps
Reversible vaporcompression cycle
Closed ground loop heatexchanger
Water or Water/antifreezesolution
Most common typeWater-to-air heat pump
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Focus on Geothermal Field:
Once the system is buried, it should remain
buried for 50+ years.
Repairing geothermal systems is difficult and
costly after the system has been backfilled.
Proper design, installation, and Cx willminimize the chances that the buried systemwill need repairs.
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GCHP Further Subdivided
Type of ground heat exchanger design
Vertical vs. Horizontal
Hybrid System
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Advantages of Vertical GCHP
Requires relatively small plots
Soil varies very little in temperature andthermal properties
Requires smallest amount of pipe andpumping energy
Can yield the most efficient GCHP
system performance
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Disadvantages of Vertical GCHP
Higher cost becauseof equipment needed
to drill borehole
Drill Rig
Grout
Grout Mixer
Limited experienced
contractors
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Horizontal GCHP
Advantages
Less Expensive than
vertical GCHP Residential
applications haveadequate ground area
More trainedequipment operators
Disadvantages
Larger Ground area
requirement Greater adverse
variations inperformance
Ground Temperatures
Rainfall
Burial Depth
Higher Pumping-Energy Requirements
Lower SystemEfficiencies
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Commissioning Phases
Planning
Design
Construction
Occupancy/Operations
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Commissioning Phases
Part 1: Planning Phase
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Planning Phase
Approval from DNR or other governing body
or Authority Having Jurisdiction (AHJ)
Formation & Thermal Conductivity (TC) Test to
determine ground properties
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Field Tests
Drill to desired depth
Use same pipediameter and grout
Wait 5 days
Insulate entire device
Minimum test length
= 48 hours
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Thermal Conductivity Test
Advantages
Accurate borefield size Indicates level of effort
required to insert loop
Type of drilling
Reduce Contractorsuncertainty
May reduce bid price
Can use test bore in design
Disadvantage Initial cost
Results can be inaccurate
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F&TC Test Report
Copy of Drill Log
Ground ThermalConductivity (Btu/hftF)
Ground ThermalDiffusivity (ft2/day)
Undisturbed GroundTemperature (F)
Depth to Water Table
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Water Problems
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Commissioning Phases
Part 2: Design Phase
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Design Review: What to Look For
Qualifications: Geothermal contractor
certified by IGSHPA As-built drawings of geo field required
(including GPS coordinates)
F&TC Test results Contractor to integrate test bore into the
geothermal field
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Design Review: What to Look For
Pipe and fittings shall be HDPE classified for
geothermal installation (IGSHPA) 50 year warranty provided by pipe manufacturer
Heat transfer fluid must be approved by DNR orState Regulatory Agency
Locating Wire and Warning Tape
Thermal Grout: TC of at least 1.0 Btu/hr-ft-F (obtainsamples for testing)
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Thermally Enhanced Grout
80
90
100
110
120
130
Bores
0.45 0.6 0.85 1 1.2
Grout Conductivity (Btu/hftF)
200-Ton, 300' deep Vertical System
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Design Review: What to Look For
Header Pit Vault HDPE classified for geothermal installations
Factory pressure tested no leaks at 1 psi air test for at least 30minutes
Entry to vault minimum 28 diameter, neoprene gasket on lid,traffic rated frame and cover if located in traffic area.
Ladder Conform to current OSHA guidelines Anti-buoyancy calculations amount of concrete needed to
anchor vault
Valves: Isolation valve on supply line of each circuit. Balancing
valve on return line of each circuit. P/T port on each supply and return main and all circuit pipes
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Vault Installation
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Header Pit Vault
Circuits routed tounderground vault
o Typically 3 Dia Circuits
o Balancing Valves
Only two pipes go backto building
Concrete vs HDPE
o
Concrete cheapero HDPE water tight
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Design Review: What to Look For
Pressure Testing
Flushing and PurgingGrouting
Backfilling
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Design Review: What to Look For
Borefield Design
Minimum bore spacing Bore depth
Reverse Return piping configuration
Minimum burial depth of lateral pipes (based on frost layer
depth)
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Frost Layer
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Example: 100 Bore System
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Circuit
Below Grade in Sand Bedding
Reverse Return Balanced Flow
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Commissioning Phases
Part 3: Construction Phase
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Construction Verification
Before Excavation Begins
Contractor Qualifications
Shop drawings must be approved prior to ordering materials orstarting work
Site Erosion Control Plan in place
DNR and/or State Regulatory Agency approval
Timing is critical
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Construction Verification
During Excavation / Drilling / Pipe Installation Bore spacing / depth
Materials on site: pipes, grout, backfill materials, vault, etc.
Lateral pipe (trench) depth below frost line
Grouting Procedure
Must grout within 24 hours of drilling. No more than four un-grouted
boreholes at any one time. Test grout mixture samples early.
Seal open ends of pipes to prevent entry of contaminants
Timing of verification is critical
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Open Pipe Ends
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Construction Verification
Prior to Backfilling Pressure Testing successful and witnessed
Test with water, NOT air
Flushing and Purging successful and witnessed
At least 2 ft/sec to remove air and debris
Bedding material (sand) is free of rocks, clay, and sharp objects
Locating wire installed on pipes Location of bores and pipes have been surveyed as-built
drawings are accurate
Did I mention that timing of verification is critical?
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Unapproved Pipe Bedding
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Construction Verification
During Backfilling
No backfilling in freezing weather or with frozen materials
Warning tape installed approximately 36 above pipes
C
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Commissioning Phases
Part 4: Occupancy/Operations Phase
S M i
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System Maintenance
Borefield is essentially maintenance-free
Verify glycol concentrationVerify system pressure
Check fluid temperatures range of 30F to 100F isnormal
Annual check of vault interior (if applicable)
C li & H ti EWT Effi i
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Cooling & Heating EWT - Efficiency
0
1
2
3
4
5
6
20 30 40 50 60 70 80 90 100
Entering Water Temp (F)
COP_
0
5
10
15
20
25
EER_
EER & COP
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EER & COP
EER = Energy Efficiency Ratio
Cooling Mode Typical Range 18-27 EER
COP = Coefficient of Performance
Heating Mode
Typical range 2.8-4.0 COP
)(
)/(
WInputElectrical
hrBtuOutputCoolingEER =
)/(
)/(
hrBtuInputElectrical
hrBtuOutputHeatingCOP =
R
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Resources
1. Kavanaugh, S.P., K. Rafferty. 1997. Ground-Source Heat Pumps:Design of Geothermal Systems for Commercial and InstitutionalBuildings, ASHRAE.
2. 2007 ASHRAE Handbook-HVAC Applications, Chap. 32.
3. 2008 ASHRAE Handbook-HVAC System & Equipment, Chap. 48.
4. 1988. Closed-Loop Ground-Source Heat Pump Systems:Installation Guide, Oklahoma State University & International
Ground Source Heat Pump Association.
5. Wisconsin Department of Natural Resources. http://dnr.wi.gov
6. U.S. Department of Energy, EERE Program.http://www.eere.energy.gov
Q estions?
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Questions?
AIA Quality Assurance
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AIA Quality Assurance
Portland Energy Conservation, Inc is a registered provider with TheAmerican Institute of Architects Continuing Education Systems. Creditearned on completion of this program will be reported to CES Records
for AIA members. Certificates of Completion for non-AIA members areavailable on request.
This program is registered with the AIA/CES for continuingprofessional education. As such, it does not include content that maybe deemed or construed to be an approval or endorsement by the AIAof any material of construction or any method or manner of handling,using, distributing, or dealing in any material or product. Questions
related to specific materials, methods, and services will be addressedat the conclusion of this presentation.
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THANK YOU
Kenneth Von Bank, PE, CCP