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Geothermal Respose TestBorder ConditionsMeasurements at IAG Test Site Darmstadt, WillichTechnical University of Darmstadt

Clemens Lehr

GRT Workshop Prague

Geotechnik LehrDevelopment of Measuring Tools and Measuring Service:

Geothermal Response Test (GRT, eGRT)Fiber Optical Systems: Distributed Temperature Sensing (eGRT),Strain, Pressure, Accelerometer Grout Control – Digital Recording of Flow, Density and Pressure while Grouting Flow Rate and Yielding Resistance Test, Pressure and Tightness Test on Borehole Heat Exchanger Temperature Depth Profiles, Groundwater Detection, Grout Survey Ultra Slim Probes BHE Logs - Susceptibility, Deviation, Temperature, Depth Survey Dimensioning of BHE Arrays and Heat Pump Systems Technical Equipment for Engineers and Designers, Courses of Instruction

Software DevelopmentTRT 2.0 Software for Evaluation of Geothermal Response Test and Enhanced Geothermal Response Test Data. SF numerical Software for Dimensioning and hydro-thermical Simulations.

EA GeothermieThe Geothermal Energy Study Group was set up in Bochum in 2004 and became the joint DGGV/DGGT study group in 2007. Some 20 specialists from universities, authorities and engineering consultants are active in the group and meet two or three times a year.

Lecturer at Technical University of Darmstadt (Institute of Applied Geosciences)

Member of German Geothermal Society, German Heating Pump Society, International Geothermal Society (IAG)

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+

3

Overview former Investigations

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Test Site Darmstadt

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Hybrid Cable

BHE

Grout

B 2

Hybrid Cable

Quaternary

GranodioriteWeathering Zone

5

GranodioriteGranular

Desintegration Zone

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Density (dry)Thermal Conductivity Porosity

saturated

dry

Dep

th[m

]

Labortory Tests Drilling Core B2

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Date Time Power

Air

Tem

per

atu

re[°

C]

Effe

ctiv

eTh

erm

al C

on

du

ctiv

ity

[W /

(m

K)]

GRT Coaxial- BHE

GRT Duplex-U-BHE

Moving Avarage7 Days

January 2009 July 2009 January 2010 July 2010 January 2011 July 2011

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Date Time Power A

ir T

emp

erat

ure

[°C

]

July 2010 January 2011 July 2011 January 2012 July 2012

EGRT Duplex-U- BHE

EGRT Coaxial- BHE

8

Moving Avarage7 Days

Effe

ctiv

eTh

erm

al C

on

du

ctiv

ity

[W /

(m

K)]

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Measurements in 2016

5 Different Measurement Devices at B 2

6 Different Evaluation Methods:

Evaluation by Device owning Company/ InstitutionEvaluation via TRT 2.0 Software:Line Source – Averaged Heating PowerLine Source – Variable Power/ SuperpositionCylinder Source – Averaged Heating PowerCylinder Source – Variable Power/ Superposition

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TEST SITE WILLICHOn the Test Site Willich various Configurations and Combinations of Borehole Heat Exchangers and Heat Pumps will be examined. In a first Step the thermo-physical Environment will be determined. Thereafter different Combinations of BHE Types and Heat Pumps under realistic operation Conditions will be investigated. As a Result Temperature Behavior and Efficiency of the Settings are analyzed. Comparison of various Borehole Heat Exchanger Types and Grouting

3 Duplex-U-BHE 32 mm, 30 m3 Coaxial-BHE Ø 140 mm (Heat-Storage-BHE), 30 m3 Single-U-BHE 40 mm, 30 m

Each Type of BHE were completed with 3 Kinds of Grouting Materials:

Simple Grouting (λ 1,2 W/(mK))Enhanced Grouting (λ 2,0 W/(mK))Clay Pellets (λ 1,2 W/(mK))

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Each BHE is equipped with Flowmeter and Temperature Sensors. Flow Rate and Temperatures are recorded to Analyze different operational Configurations.

Each BHE is equipped with Flowmeter and Temperature Sensors. Flow Rate and Temperatures are recorded to Analyze different ope

a) Single-U-BHE b) Duplex-U-BHE c) Coaxial-BHE.Source: EA Geothermie, Graphics after: Sass & Mielke 2012

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Border Conditions

Geology and Environment

- Vast homogeneous Geology (e.g. Granite, Clay, etc.)

- Low Groundwater Influence

- Groundwater Observation Wells

- Weather Station

-Technical

-Stable Power Supply

13Geothermie-Kongress Dortmund 201406.03.2014 C. Lehr

Drilling

Cored Drilling

Geophysical Survey

Geophysical Investigation on Cores (e.g. Thermo-Scanner, Porosity, Saturation, etc.)

Controlled Completion

- Straight Completion with Spacers

- Monitored Grouting

-Thermophysical Approval -> Backfilling

-Thermopysical Investigation -> Border Conditions/ Groundwater/ EGRT

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Cross Section

Borehole

BHE

Cable Strap

Spacer

Square Tubing

14

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Missing Grout

°C

Time [s]

Depth

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Undesturbed Start Heating Phase End Heating Phase Circulation

Groundwater Flow

Minute

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EA-Geothermie - Recommendations on Design,

Construction, Operation and Monitoring (2016)

The recommendations summarise the state of the art. Their aim is the proper exploitation of the ground for geothermal purposes without adversely affecting the ground or the groundwater on the one hand and the operation of the system and nearby buildings on the other. The recommendations should be used during consulting, design, installation and operation in order to achieve optimum and sustainable use of the ground at a specific location. Authorities responsible for supervising and approving projects can use the recommendations as a guide when taking decisions and making stipulations.

Edited by German Geological Society e.V. (DGGV)

and German Geotechnical Society e.V. (DGGT).

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Thank You !

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The result of the evaluation of GRT data by inverse numerical approximation of theT(t)-Curve (Best Fit) is the effective thermal conductivity [𝜆𝑒𝑓𝑓] and the effective volumetric heat

capacity. The effective values include conductive and convective thermal flow.The evaluation is based on Kelvin‘s Line Source or Cylinder Source Approach.

∆𝜈 𝑟, 𝑡 =ሶ𝑄𝐻

4𝜋𝜆𝑒𝑓𝑓𝐸𝑖

𝑟2

4𝛼𝑡

𝛼 = 𝑡ℎ𝑒𝑟𝑚𝑎𝑙 𝑑𝑖𝑓𝑓𝑢𝑠𝑖𝑣𝑖𝑡𝑦 Τ𝑚2 𝑠𝐸𝑖 = 𝑒𝑥𝑝𝑜𝑛𝑒𝑛𝑡𝑖𝑎𝑙 𝑖𝑛𝑡𝑒𝑔𝑟𝑎𝑙

ሶ𝑄𝐻 = 𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 ℎ𝑒𝑎𝑡𝑖𝑛𝑔 𝑝𝑜𝑤𝑒𝑟 Τ𝑊 𝑚𝑟 = 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑜 ℎ𝑒𝑎𝑡𝑖𝑛𝑔 𝑠𝑜𝑢𝑟𝑐𝑒 𝑚Δ𝜐 = 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 𝑡𝑜 𝑢𝑛𝑑𝑒𝑠𝑡𝑢𝑟𝑏𝑒𝑑 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑢𝑛𝑑𝑒𝑟𝑔𝑟𝑜𝑢𝑛𝑑 𝐾𝜆𝑒𝑓𝑓 = 𝑒𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒 𝑡ℎ𝑒𝑟𝑚𝑎𝑙 𝑐𝑜𝑛𝑑𝑢𝑐𝑡𝑖𝑣𝑖𝑡𝑦 Τ𝑊 𝑚𝐾

𝜋 = 𝑃𝑖 3.141

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Ingersoll & Plass (1948) were presenting an approximate solution.

Recently GRT results are still evaluated in using the linear steady state like behaviour(straight line method) which is a simplified derivation from Ingersoll & Plass equation.

Using this simplified simplification leads to a loss of important informations [e.g. near field information at beginnig of the test, volumetric heat capacity is not determinable].

4

Heff

Q

bHH

f RQr

tQTtT

20

4ln

4)(

Simplyfications