Casasso A

Chicco J

Della Valentina S

Giordano N

Mandrone G

Raymond J

Sethi R

English

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08 November 2022POLITECNICO DI TORINORepository ISTITUZIONALEMapping the geothermal potential of a borehole heat exchanger in Kuujjuaq, Québec, Canada / Della Valentina, S;Chicco, J; Giordano, N; Casasso, A; Sethi, R; Mandrone, G; Raymond, J. - (2018). ((Intervento presentato al convegnoRFG 2018 PREMIER CONFERENCE ON ENERGY - MINERALS - WATER - THE EARTH nel Giugno 2018.OriginalMapping the geothermal potential of a borehole heat exchanger in Kuujjuaq, Québec, CanadaPublisher:PublishedDOI:Terms of use:openAccessPublisher copyright(Article begins on next page)This article is made available under terms and conditions as specified in the  corresponding bibliographic description inthe repositoryAvailability:This version is available at: 11583/2915358 since: 2021-07-27T14:36:52ZVancouver Convention CenterRESOURCES FOR FUTURE GENERATIONPREMIER CONFERENCE ONENERGY - MINERALS - WATER - THE EARTHJUNE 16 - 21 | VANCOUVER CONVENTION CENTERVANCOUVER, BC, CANADACONTACTS Nicolò Giordano nicolo.giordano@ete.inrs.caABSTRACTMapping the geothermal potential of a borehole heat exchanger in Kuujjuaq, Québec, Canada.S. Della Valentina1, J. Chicco2, N. Giordano3, A. Casasso1, R. Sethi1, G. Mandrone2, J. Raymond31 Dipartimento di Ingegneria dell’Ambiente, del Territorio e delle Infrastrutture, Politecnico di Torino - Corso Duca degli Abruzzi, 24 - 10129 Torino (IT)2 Dipartimento di Scienze della Terra, Università di Torino - Via Valperga Caluso, 35 - 10125 Torino (IT)3 Centre Eau Terre Environnement, Institut national de la recherche scientifique - 490, Rue de la Couronne - G1K 9A9 Québec, QC (CA)GEOLOGICAL SETTING & THERMAL PROPERTIESFigure 2 - Map of the quaternary sedimentsKuujjuaq (58.10°N, -68.42°E) is located in the west part of SoutheasternChurchill Province, part of the Canadian Shield (Fig. 1). The mainlithological units present in Kuujjuaq and surroundings are diorites andgabbros from “Complexe de Kaslac” (1.8 Ga), tonalitic gneisses of “Plutonde Kuujjuaq” (1.8 Ga) and granoblastic paragneisses of the “Suite de laBaleine” (Archean to Paleoproterozoic) (Simard et al., 2013).Figure 3 - Thermal conductivity and heat capacity of quaternary sedimentsand rock samples in saturated conditionsMETHODOLOGYRESULTS & DISCUSSIONREFERENCESCasasso, A. and R. Sethi. 2016. G.POT: A quantitative method for the assessment and mapping of the shallow geothermal potential. Energy, 106: 765-773.Fortier, R. et al. 2011. Cartographie des dépôts quaternaires des villages nordiques de Whapmagoostui-Kuujjuarapik, Umiujaq, Salluit et Kuujjuaq. Rapport de synthèse de la phase I, MDDEPQ, GM 65971.Raymond, J., et al. 2017. The geothermal open laboratory: a free space to measure thermal and hydraulic properties of geological materials. IGCP636 Annual Meeting, Santiago de Chile.Simard, M. et al. 2013. Géologie de la région de Kuujjuaq et de la baie d’Ungava (SRNC 24J, 24K). Québec, Canada: Gouvernement du Québec.Figure 1 - Geological mapത𝑄𝐵𝐻𝐸 =0.0701 · 𝑇0 − 𝑇𝑙𝑖𝑚 · 𝜆 · 𝐿 · 𝑡𝑐′−0.619 · 𝑡𝑐′ · 𝑙𝑜𝑔 𝑢𝑠′ + 0.532 · 𝑡𝑐′ −0.962 · 𝑙𝑜𝑔 𝑢𝑐′ − 0.455 · 𝑡𝑐′ − 1.619 + 4𝜋𝜆 · 𝑅𝑏With: 𝑢𝑐′= Τ𝜌𝑐 · 𝑟𝑏2 4𝜆𝑡𝑐 , 𝑢𝑠′ = Τ𝜌𝑐 · 𝑅𝑏2 4𝜆𝑡𝑠 , 𝑡𝑐′ = 𝑡𝑐/𝑡𝑦Parameter Symbol Value UnitThreshold fluid temperature Tlim -3 °CBorehole depth L 100/ 200/ 300 mUndisturbed ground temperature 𝑻𝟎 1.0/ 1.75/ 2.75 °CBorehole radius rb 0.038 mSimulated lifetime ts 50 yearsLength of the heating season 𝒕𝒄 270 daysBorehole thermal resistance Rb 0.1 mK/WTable 1 – Parameters adopted for the application of the G.POT method in KuujjuaqFigure 6 – Shallow geothermal potential in Kuujjuaq according to different BHE lengths: a) 100 m; b) 200 m; c) 300 m.Three different maps of geothermal potential has been drawn (Fig. 6) to compare three different BHE lengths. Due mainly to the reduced range of variation ofthermal conductivity values, the small surface considered and the minimal altitude differences, values of geothermal potential are very homogenous.The G.POT (Casasso and Sethi, 2016) method was adopted for the estimationof the geothermal potential (QBHE). This method provides an empiricalrelationship (Eq. 1) involving thermal properties of the ground and the BHE,and operational/design parameters of the plant (Tab. 1). It allows the estimationof the maximum sustainably exchangeable energy of a BHE in a homogeneousporous medium.Equation 1GROUND TEMPERATURE &THERMAL LOADSThe shallow underground temperature inthe study area is slightly higher than 0°Cand the vertical geothermal gradient is verylow (Fig. 4). This is a limiting factor forthe efficiency of geothermal applications.The average undisturbed groundtemperature over the length of the borehole(𝑇0) was estimated in 1.0 °C, 1.75 °C and2.75 °C over the first 100, 200 and 300 m.The total annual demand for space heatingand domestic hot water of a typical semi-detached house in Kuujjuaq is around 43MWh/y (Fig. 5).BHE length (m)Geothermal Potential (MWh/y)BHEsrequiredTotal drilled length (m)100 3.7 12 1200200 9.0 5 1000300 16.5 3 900Table 2 – BHE to be drilled in Kuujjuaq to cover 43 MWh/yFigure 5 –Annual thermal loads (MWh)The geothermal potential increases more than linearly with the length of the borehole, thanks to thehigher temperatures reached and the lower influence of shallow less conductive quaternary deposits.In the municipal territory, the potential ranges from 3.4 to 4.2 MWh/y in the 100 m case; from 8.6 to10.0 MWh/y in the 200 m case; from 15.8 to 18.2 MWh/y in the 300 m case. The energy demand ofa typical semi-detached house in Kuujjuaq (43 MWh/y, Fig. 5) can be fulfilled by 12, 5 and 3boreholes respectively, with total drilled lengths decreasing from case 1 to 3 according to theincreasing potential (Tab. 2).Ground thermal conductivity (𝜆) and heat capacity (𝜌𝑐) maps were realisedaccording to the laboratory analyses shown in Fig. 3 and considering thepresence and thickness of quaternary deposits.02468JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DECInuit communities of Nunavik, Northern Québec, strongly rely on fossil fuels for building’s space heating. Diesel furnaces are spread in all the 14 Inuit villages, totalizing 12,000inhabitants and situated along the coast of the Ungava Peninsula. A feasibility study has been carried out in Kuujjuaq, the capital of Nunavik, to evaluate the possibility of usinglow-enthalpy geothermal energy as a renewable and sustainable heating source. The present contribution highlights the geothermal potential of a borehole heat exchanger (BHE)calculated with the G.POT method. This method is based on a simplified heat transfer model taking into account ground thermal properties and a wide range of installationdesign parameters. The main constraints of the surveyed area are related to the low underground temperature, with discontinuous permafrost depending on the local geologicalconditions, and high building heating needs with over 8,500 heating degree day below 18°C. Different borehole characteristics were analyzed, according to the technologiesavailable in the area. A geothermal potential of 3.8 MWh/y has been calculated for a 100 m deep borehole installed in the town center and it is highly influenced by the thresholdtemperature of the heat carrier fluid. This result is low if compared to common applications in the south, but the high cost and the adverse environmental effects of fossil fuelscurrently used allow to consider shallow geothermal energy as a possible solution for the area of Kuujjuaq.Figure 4 – T-depth profile in W18The quaternary sediments mainly consist of littoral and pre-littoralsediments alternating to intertidal deposits related to different cycles oftransgression and regression of the Iberville sea (Fig. 2). From a geo-morphological point of view, two small parallel valleys can be highlightedin the territory of Kuujjuaq, both of them southward degrading to theKosoak River whose estuary outlets in the Ungava Bay around 50 km inthe NNE direction. Glacial till deposits often cover bedrock outcrops andit is common to find them underlying the marine sediments. Alluvialcoarse grained materials are only found along the small streams of theabove mentioned valleys (Fortier et al., 2011).Thermal conductivity and heat capacity were analysed in the laboratory bya needle probe for the unconsolidated quaternary sediments and by a heatflow meter for the rock samples (Fig. 3, Raymond et al., 2017).Sediments Rocksa) b) c)

Mapping the geothermal potential of a borehole heat exchanger in Kuujjuaq, Québec, Canada

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Mapping the geothermal potential of a borehole heat exchanger in Kuujjuaq, Québec, Canada

Mapping the geothermal potential of a borehole heat exchanger in Kuujjuaq, Québec, Canada

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