13 Ncbc-2011-Validating Energy Sources-Von Bank

7/23/2019 13 Ncbc-2011-Validating Energy Sources-Von Bank

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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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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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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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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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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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Pressure Testing

Flushing and PurgingGrouting

Backfilling


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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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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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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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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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During Backfilling

No backfilling in freezing weather or with frozen materials

Warning tape installed approximately 36 above pipes

C


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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?



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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

13 Ncbc-2011-Validating Energy Sources-Von Bank

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