Implementation of the Distributed Thermal Response Test at Characteristic Geological Regions throughout Croatia

Transcription

1 Implementation of the Distributed Thermal Response Test at Characteristic Geological Regions throughout Croatia Vladimir SOLDO* Leon LEPOŠA* Luka BOBAN* Staša BOROVIĆ** *University of Zagreb, Faculty of Mechanical Engineering and Naval Architecture, Croatia **Croatian Geological Survey Results of the research were obtained within the project Research and the promotion of use of shallow geothermal potential l in Croatia This project is funded by the European Union under contract number IPA2007/HR/16IPO/ ,, in the amount of ,36 EUR This publication has been produced with the assistance of the European Union. The content of this publication are the sole responsability of the authors and can in no way be taken to reflect the views of the European Union.

2 CONTENT 1. INTRODUCTION 2. BOREHOLE HEAT EXCHANGER INSTALLATION 3. METHODOLOGY - Determination of ground thermal properties 4. RESULTS AND DISCUTION 5. CONCLUSION AND FUTURE WORK 1. Introduction This paper presents the results of the EU IPA project Research and the promotion of use of shallow geothermal potential in Croatia Aims of the project: - determination of the thermal properties of shallow geothermal potential in characteristic regions throughout the Republic of Croatia - promotion of application of GSHP technology as renewable energy source. Research is carried out on eight different locations that include different geologicaly regions. The improved method for evaluation of the local thermal conductivity in the soil and the thermal resistance of a borehole heat exchanger known as Distributed Thermal Response Test (DTRT) is used (implementation of the fiber optic cables). The work presented in this paper shows measurements from the first borehole heat exchanger installation located in the city of Osijek, Croatia, and determination of ground thermal conductivity of the soil using three different approaches. 4

3 1. Introduction IPA PROJECT: Reference of the Call for Proposal Project title Beneficiry Partner Associates Locations ot the action IPA IIIC, Operation Science and Innovation Investment Fund/SIIF, 2nd call, phase II, IPA2007/HR/16IPO/ , EuropeAid/131920/M/ACT/HR, Grant sheme Research and the promotion of use of shallow geothermal potential in Croatia University of Zagreb, Faculty of Mechanical Engineering and Naval Architecture Croatian Geological Survey 6 technical high schools and one institute Counties: Osječko-baranjska, Požeško-slavonska, Međimurska, Grad Zagreb, Ličko-senjska, Istarska, Zadarska, Šibensko-kninska Implementation period 24 months ( ) Budget ,36 eur (sufinancing ,53 eur; 17,88 %) 5 1. Introduction Drilling locations throughout Croatia Associate (1) Techcical school Čakovec Associate (3) Vocational School Gospić Associate (4) Technical school Osijek Associate (6) Technical school Požega Associate (7) Technical school Zadar Associate (2) Vocational school king Zvonimir Knin Associate (5) Institute of Agriculture and Tourism Poreč Beneficiry (8) Faculty of Mechanical Engineering and Naval Architecture, Zagreb 6

4 2. Borehole heat exchanger installation In mid April 2014 the project implementation started with drilling of a 100 m deep borehole of 152 mm in diameter in the vicinity of Technical school in Osijek Soil properties determination - CGS Drilling with soil sampling on location Osijek (23 April 2015) 7 2. Borehole heat exchanger installation Together with the BHE in the form of a double polyethylene U-pipe, the fiber optic cable was inserted into the borehole After the installation of borehole heat exchanger, the borehole was filled with a special grouting material mm fiber optic cables 2 - U tube 3 - distance holder 4 - grouting material Figure 1: a) Position of the optical cables inside the U pipe BHE; b) The optical cables installed inside the U pipe 8

5 3. Methodology As part of this project three different approaches were applied for determination of ground thermal conductivity: 1. Direct measurement of sediment thermal properties (CGS) 2. Conventional Thermal Response Test TRT (FMENA) 3. Distributed Thermal Response Test DTRT (FMENA) Temperature measurement along the borehole heat exchanger was carried out with fibre optic cable coupled with AP Sensing Linear Pro Series DTS instrument. Multimode 50/125 fiber optic cable is installed in both tubes of U-pipe borehole heat exchanger (Fujii 2006, Acuna 2008) 9 3. Methodology Ø The obtained thermal properties are presented according to the characteristic ground layers with their respective thickness. Borehole sections 10

6 3. Methodology After BHE installation 2 weeks of ground stabilization I. phase: Undisturbed temperature measurement 72 hours II. phase: Thermal response test 48 hours III. phase: Borehole recovery 48 hours Thermal response test (TRT) was performed with GeoGert 2,0 - injection heat power: 8,2 kw - water flow rate: 0,34 l/s Results and discussion Temperature [ C] Temperature [ C] 14,0 14,5 15,0 15,5 16, h 48 h Borehole depth [m] Upward flow tube Downward flow Borehole depth [m] Downward flow ( :45h) Upward flow ( :45h) Downward flow ( :55h) Upward flow ( :55h) Fluid mean temperature ( :55h) Undisturbed ground temperature profile Temperature distribution along borehole during the DTRT (location Osijek) 12

7 4. Results and discussion W/(m K) R b, (K m)/w 0 0,02 0,04 0,06 0,08 0,1 0, Section interval, m Section interval, m Thermal conductivity of the ground Borehole thermal resistance Ground thermal conductivity varies from 1,52 W/(m K) to 2,3 W/(m K), which is in accordance with the results obtained by the experts from the Croatian Geological Survey. The difference between thermal conductivity in each sector occurs because of the different soil layer along the borehole. The result of averaging all the sectors results is equal to 1,93 W/(m K) Results and discussion Ø Results obtained with 3 different medthods are as follows: Ground thermal conductivity, λ [W/mK] Borehole thermal resistance, R b [Km/W] Direct measurement of sediments 1,80 - Thermal Response Test 1,92 0,0932 Distributed Thermal Response 1,93 0,0900 Test 14

8 Present works Osijek Čakovec Požega Soil samples on 8 locations Zadar Gospić Zagreb Poreč Knin 15 Present works On going activities: - Analysis of the measurement results Ground thermal conductivity λ, W/(m K) Undisturbed ground temperature soil, C 16

9 FUTURE WORKS Application of the GSHP technology Equiping the heat pump system with sensors - Measurement of the SPF - Heat pump, Frigo Plus d.o.o. - Heating cappacity 8,6 kw (B0/W45) Conclusion In this paper Distributed Thermal Response Test was applied for determination of vertical distribution of the ground thermal properties TRT and DTRT shows good agreement for ground thermal conductivity, while TRT slightly overestimates borehole thermal resistance (by 4% percent). This project setting pocedures for testing of shallow geothermal resources in Croatia. For the future research it is planning to equip the heat pumps on 8 locatins with monitoring system (SPF measurement) 18

10 Thankyouforyourattention! Prof.Dr. Vladimir Soldo, project leader; Leon Lepoša, Ph.D. student; Luka Boban, Ph.D. student; University of Zagreb, Faculty of Mechanical Engineering and Naval Architecture Staša Borovic, Ph.D. student; Croatian Geological Survey 19