KBS-3 and very deep borehole (VDH) concepts are two major types of long-term geologicaldisposal methods for high-level radioactive waste (HLW) isolating from the biosphere. TheKBS-3V concept for isolating the HLW at the depth of 400-500 m, is the officially proposedoption in Sweden and has been the subject of considerable research in the past few decades,while the VDH concept was considered as an option in the 1950s but later became discouragedbecause of insufficient experience in drilling technology. The greatest merit of the VDHconcept is that the almost stagnant groundwater in the deep boreholes prevents the transport ofthe possible release of radionuclides into the rock or up to the ground level. Since variousdisadvantages of the KBS-3V concept were found in previous research, the superiority of VDHconcept attracted the researchers to continue studying it into the late 1980s.The geological repositories of both of KBS-3V and VDH types primarily consist of a naturalbarrier (host rock) and of an engineering barrier (also known as a buffer/backfill barrier).According to the principle of IAEA and national relative research organizations, thebuffer/backfill material should have low permeability and good expandability, as well assuitable physical and sealing properties.The thesis concerns the VDH concept and is focused on the construction and performance ofthose parts of the sealed repository that are not affected by high temperature or gamma radiation.In the lower part of a VDH repository, the clay packages containing HLW will be exposed tohigh temperature (100-150 􀄇 ) in the borehole and to highly saline groundwater. In theinstallation phase of HLW, the groundwater will be pumped out and replaced by medium-softsmectite clay mud in which the HLW packages are installed vertically. During the hydrationand maturation of the clay components, the microstructural reorganization, water transport,migration of clay particles and redistribution of the density of the components take place. Thematuration determines the transient evolution of the clay seals and influences the rheologicaland soil mechanical behavior in the installation phase. The maturation of clay system alsodetermines their ultimate sealing potential of VDH repositories.This study presents the work carried out for investigating the maturation of the buffer-backfillclay in the HLW deep borehole. Initially in the study three types of clays, the Namontmorillonite,magnesium-rich and illite-smectite mixed layer clays, were examined for estimating their performance as the barrier candidate material. This is mainly presented in theliterature review. The experimental study was conducted on montmorillonite GMZ clays andI/S mixed-layer Holmehus clay. The expandability and permeability tests were carried out forinterpretation of the recorded swelling development and assessment of the effect of the salineconditions, with the goal of deriving a relationship between swelling pressure and hydraulicconductivity for different dry densities. The maturation tests of initially fully-saturatedHolmehus clay and partly saturated GMZ clay were performed. During the tests, the shearstrength mobilised by the relative movement of densified mud and migrated dense clay -contained in a perforated central tube - were determined. According to the results of shearstrength tests, the maximum operation time or the number of clay packages to be placed in asingle operation was evaluated, whilst the suitable saturation degree of the dense clay wasdiscussed as well.A model of the maturation of initially water-saturated clay seals based on Darcy’s law wasworked out and the evolution of the clay components in a lab-scale borehole using Holmehusclay were performed and compared with the experimental recordings. Good agreementsbetween the physical behaviors of the theoretical simulations and the measurements wasachieved by which the validity of the model was verified. Using the results, the hydration andsoil migration in the entire maturation process were presented in diagram. The model was alsoused for preliminary evaluation of the maturation products in real boreholes by assuming thesame Holmehus clay as used in the tests. Two constellation of borehole and dense clay withdifferent diameters, 80 cm borehole /60 cm clay and 80cm/50cm, were assumed. The resultsrespecting dry density and hydraulic conductivity of the ultimate maturation products, and thedegree of homogeneous of the buffer and backfill clay system in the assumed boreholes, arepresented and discussed. The options of different mineral types and initial physical propertiesof the candidate buffer clays provide a reference for engineering barrier design of HLW disposalin VDH.

The sales of Ground Source Heat Pumps in Sweden and many other countries are having a rapid growth in the last decade. Today, there are approximately 360 000 systems installed in Sweden, with a growing rate of about 30 000 installations per year. The most common way to exchange heat with the bedrock in ground source heat pump applications is circulating a secondary fluid through a Borehole Heat Exchanger (BHE), a closed loop in a vertical borehole. The fluid transports the heat from the ground to a certain heating and/or cooling application. A fluid with one degree higher or lower temperature coming out from the borehole may represent a 2-3% change in the COP of a heat pump system. It is therefore of great relevance to design cost effective and easy to install borehole heat exchangers. U-pipe BHEs consisting of two equal cylindrical pipes connected together at the borehole bottom have dominated the market for several years in spite of their relatively poor thermal performance and, still, there exist many uncertainties about how to optimize them. Although more efficient BHEs have been discussed for many years, the introduction of new designs has been practically lacking. However, the interest for innovation within this field is increasing nowadays and more effective methods for injecting or extracting heat into/from the ground (better BHEs) with smaller temperature differences between the heat secondary fluid and the surrounding bedrock must be suggested for introduction into the market. This report presents the analysis of several groundwater filled borehole heat exchangers, including standard and alternative U-pipe configurations (e.g. with spacers, grooves), as well as two coaxial designs. The study embraces measurements of borehole deviation, ground water flow, undisturbed ground temperature profile, secondary fluid and groundwater temperature variations in time, theoretical analyses with a FEM software, Distributed Thermal Response Test (DTRT), and pressure drop. Significant attention is devoted to distributed temperature measurements using optic fiber cables along the BHEs during heat extraction and heat injection from and to the ground. / <p>QC 20100517</p> / EFFSYS2 / Efficient Use of Energy Wells for Heat Pumps

In order to reduce emissions from the building sector, which stands for than a fifth of the global energy consumption today, efficient and fossil free heating and cooling systems are of importance. This study investigates the combination of solar photovoltaic thermal collectors and ground source heat pump systems in order to regenerate energy to the ground in combination with free cooling. Research questions investigated was how techno-economically efficient a system with photovoltaic thermal collectors, ground source heat pumps and free cooling in a commercial building is. Moreover, the study evaluates what benefits and challenges such system can have. In addition, Polysun as a modeling tool was evaluated for modeling a system includingthese components. Polysun was used as a model tool to first set up a replication of an existing system in TRNSYS provided by researchers at KTH. The model was then scaled and adjusted with parameters to represent a commercial building using free cooling from Vasakronan, a Swedish property company. Photovoltaic thermal collectors were added to the model of the existing building, with two different configurations, and the heating and cooling demand of the building was varied. The results showed that a configuration with photovoltaic thermal collectors added after the evaporator side of the heat pump generated more energy to the system compared with an installation before the evaporator side of the heat pump. The possibilities of free cooling decreased with increasing number of solar collectors, due to the rise of temperature in the ground. From an economic perspective, photovoltaic thermal collectors are more expensive than photovoltaic modules, since it has an additional cost for the hydraulic system that depends on the building. However, photovoltaic thermal collectors also provide thermal energy that can help balancing borehole systems and reduce the risk for a need of additional drilling. The study performed an uncertainty and sensitivity analysis of the results, showing that the electricity price is the most sensitive parameter to the net present value of investing in photovoltaic thermal collectors. With the electricity price assumed in this study, the net present values were positive for all cases for the given interest rate and lifetime of 25 years. It was also concluded that the modeling tool Polysun has a user friendly interface where energy systems easily can be modeled. In terms of borehole configurations, there is a lack of modeling alternatives which resulted in unexpected temperature rises in the ground for the model. / Byggnadssektorn står idag för mer än en femtedel av den globala energiförbrukningen, där över hälften av energin kommer från fossila bränslen. Därför är det viktigt med effektiva och fossilfria uppvärmnings- och kylsystem för att minska utsläppen, där värmepumpar är ett bra alternativ. Denna studie undersöker kombinationen av termiska solceller och bergvärmepumpssystem i kommersiella fastigheter, med syfte att återladda energi till marken i kombination med frikyla. Syftet var att undersöka hur teknoekonomiskt effektivt ett sådant system är och vilka fördelar samt nackdelar som finns. Dessutom utvärderades modelleringsverktyget Polysun som användes föratt modellera systemen. Arbetet inleddes med att efterlikna ett befintligt system i Polysun från en tidigare studie från KTH som använt modelleringsverktyget TRNSYS. Därefter justerades detta system så att det skulle efterlikna en av Vasakronans byggnader som idag använder bergvärme och frikyla. Tre scenarier konstruerades till basmodellen där samtliga innefattade termiska solceller. Resultaten visade att antalet termiska solceller kunde minska i antal då dessa var kopplade efter förångarsidan av värmepumpen, jämfört med om de är installerade före förångarsidan av värmepumpen. Genom att öka antalet termiska solceller i systemet ökade temperaturen i borrhålen, vilket ledde till en minskad möjlig användning av frikyla. Ur ett ekonomiskt perspektiv är termiska solceller dyrare än solceller som enbart genererar elektricitet, med en extra kostnad för det hydrauliska systemet som även beror på byggnadens utformning. Dock finns det andra fördelar med termiska solceller såsom att de kan hjälpa till att balansera borrhålssystem och minska behovet för att borra ytterligare borrhål. I studien utfördes en osäkerhets- och känslighetsanalys av resultaten, vilken visade att elpriset har stor påverkan på nettonuvärdet av en investering i termiska solceller. Med det elpris som antogs i denna studie var nettovärdet positivt för alla fall med den givna kalkylräntan och livstiden för systemet. Polysun visade sig vara ett modelleringsverktyg med ett användarvänligt gränssnitt där energisystem lätt kan modelleras. När det gäller konfigurationer av borrhål finns det begränsade modelleringsalternativ, där resultaten visade oväntade temperaturstegringar för marken i modellen.

The devastating levee failures associated with hurricanes Katrina and Rita, and the more recent Midwest flooding, placed a spotlight on the importance of levees and our dependence on them to protect life and property. In response to levee failures associated with the hurricanes, Congress passed the Water Resources Development Act of 2007 which established a National Committee on Levee Safety. The committee was charged with developing recommendations for a National Levee Safety Program. The Secretary of the Army was charged with the establishment and maintenance of a National Levee Database. The National Levee Database is a critical tool in assessing and improving the safety of the nation's levees. However, the NLD data model, established in 2007, lacked a structure to store seepage and slope stability analyses – vital information for assessing the safety of a levee. In response, the Levee Analyst was developed in 2008 by Dr. Norm Jones and Jeffrey Handy. The Levee Analysis Data Model was designed to provide a central location, compatible with the National Levee Database, for storing large amounts of levee seepage and slope stability analytical data. The original Levee Analyst geoprocessing tools were created to assist users in populating, managing, and analyzing Levee Analyst geodatabase data. In an effort to enhance the Levee Analyst and provide greater accessibility to levee data, this research expanded the Levee Analyst to include modifications to the data model and additional geoprocessing tools that archive GeoStudio SEEP/W and SLOPE/W simulations as well as export the entire Levee Analyst database to Google Earth. Case studies were performed to demonstrate the new geoprocessing tools' capabilities and the compatibility between the National Levee Database and the Levee Analyst database. A number of levee breaches were simulated to prototype the enhancement of the Levee Analyst to include additional feature classes, tables, and geoprocessing tools. This enhancement would allow Levee Analyst to manage, edit, and export two-dimensional levee breach scenarios.

The performance of ground-source heat pump (GSHP) systems can be negatively affected over time by soil temperature degradation of boreholes (BH) in heating dominated climates. Land area is scarce in the dense urban environments typical of multi-family houses (MFH) and can lead to accelerated degradation- in tight BH fields. Heat extracted from photovoltaic thermal collectors (PVT) can help with BH regeneration; thus, limiting degradation. Additionally, free cooling (FC) is proposed in this study to tackle the anticipated cooling demandi ncrease in Sweden, while resolving the listed challenges of GSHP systems. A novel multi-source (MS) system integrating FC, PVT and GSHP together shall be investigated in this study. Firstly, implementing FC in a GSHP system for the scenario considered only provided marginal regeneration of the BH in the longterm. Both the SPF4+ and total life cycle cost (TLCC) of an FC+GSHP and GSHPsystem remained virtually constant. Furthermore, operation interference of FC and PVT in the MS system can be mitigated by considering their relative location in the system. In this study, cooling is the priority, thus placing the FC system after the BH field but before the PVT system in the brine loop is recommended. In that case, only 0.56% of the annual cooling is not delivered due to FC operation interference and the PVT thermal yield is decreased on average by 3.52%. By decreasing the BH spacing from 15 to 5 m, a slight SPF4+ increase to 3.22 is possible in a system with FC and 48 PVT collectors. With a sensitivity analysis it was shown that if a 15% decrease is achieved in electricity prices then the TLCC of this system can be lower than the TLCC of 2.13 MSEK for a GSHP system. / Prestandan hos ytjordvärmepump (GSHP) kan påverkas negativt över tid av försämrad marktemperatur i borrhål (BH) i klimat som domineras av uppvärmning. I täta stadsmiljöer med flerfamiljshus (MFH) är markytan knapp, vilket kan leda till accelererad nedbrytning i trånga BH-fält. Värme som utvinns från solfångare (PVT) kan bidra till regenerering av BH, vilket begränsar nedbrytningen. Dessutom föreslås frikyla (FC) i denna studie för att hantera den förväntade ökningen av kylbehovet i Sverige, samtidigt som man löser de listade utmaningarna med GSHP-system. Ett nytt multikällsystem (MS) som integrerar FC, PVT och GSHP tillsammans ska undersökas i denna studie. För det första gav implementeringen av FC i ett GSHP-system för det aktuella scenariot endast marginell regenerering av BH på lång sikt. Både SPF4+ och den totala livscykelkostnaden (TLCC) för ett FC+GSHP och GSHP-system förblev praktiskt taget konstant. Dessutom kan driftstörningar från FC och PVT i MS-systemet minskas genom att ta hänsyn till deras relativa placering i systemet. I denna studie prioriteras kylning, och därför rekommenderas att FC-systemet placeras efter BH-fältet men före PVT-systemet i brineslingan. Endast 0.56% av den årliga kylningen levereras inte på grund av störningar i FC-driften och PVT:s värmeutbyte minskar i genomsnitt med 3.52%. Genom att minska BH-avståndet från 15 till 5 m är en liten ökning av SPF4+ till 3.22 möjlig i ett system med FC och 48 PVT-kollektorer. En känslighetsanalys visade att om elpriserna minskar med 15% kan TLCC för detta system bli lägre än TLCC på 2.13 MSEK för ett GSHP-system.

Borehole heat exchangers are widely used in heat pumps of residential buildings and industrialsystems. It is known as one of the most energy ecient technologies which provides heatingand cooling by using sustainable geothermal energy. The life time of borehole heat exchangerslasts more than 50 years which is longer than combustion boilers. Therefore, designing abore eld with accurate sizing is important for its future applications. Due to the large volumeof the ground, the transient heat transfer process of the bore eld lasts for a long time span. Because of this, only a few of the heat transfer models for borehole ground heat exchangersare validated by experiments. Besides, experimental validation in a real scale borehole can bedicult because of the uncertainty of the composition and thermal properties of the ground. A solution to faster experimental validation is to scale down the size of the borehole andground. This report presents the construction process of a lab-scale model simulating a 4x4 bore eldof 300 m depth vertical boreholes. The process of experimental construction is describedin detail, including ground set up, conductivity test, construction of hydraulic system anddata acquisition system. The pressure drop of hydraulics system is around 2.8 bar under the a flow rate of 200 ml/min and corresponding pump speed is around 2900 to 3100 rpm. The property of the sand has been investigated through a series of conductivity tests, which shows an average thermal conductivity of 1.75 W / (m • K) and average thermal diffusivity of 8.14x10-7 m2/s. Numerical simulation (via COMSOL) is carried out for preliminary validation. Comparison of experimental and simulation results shows discrepancies and one possible reason can be: the actual heat injection rate in experiment is lower than simulation due to heat losses of hydraulic system; uncertainty of ground (saturated sand) conductivity and thermal diffusivity. / Borrhålsvärmeväxlare används ofta i värmepumpar i bostadshus och industrisystem. Det är känt som en av de mest energieffektiva teknikerna som tillhandahåller värme och kyla genom att använda hållbar geotermisk energi. Livslängden för borrhålsvärmeväxlare varar mer än 50 år vilket är längre än förbränningspannor. Därför är det viktigt att utforma ett borrfalt med exakt dimensionering för dess framtida tillämpningar. På grund av den stora markvolymen varar den transienta värmeöverforingsprocessen i borrfältet under lång tid. På grund av detta är endast ett fåtal av värmeöverföringsmodellerna för borrhålsjordvärmeväxlare validerade genom experiment. Dessutom kan experimentell validering i ett borrhål i verklig skala vara svårt på grund av osäkerheten i markens sammansättning och termiska egenskaper. En lösning för snabbare experimentell validering är att skala ner storleken på borrhålet och marken. Denna rapport presenterar konstruktionsprocessen av en modell i labbskala som simulerar ett 4x4-borrfält med 300 m djupa vertikala borrhål. Processen for experimentell konstruktion beskrivs i detalj, inklusive markuppställning, konduktivitetstest, konstruktion av hydraulsystem och datainsamlingssystem. Tryckfallet for hydrauliksystemet är cirka 2,8 bar under en flödeshastighet pa 200 ml/min och motsvarande pumphastighet är runt 2900 till 3100 rpm. Sandens egenskaper har undersökts genom en serie konduktivitetstester, som visar en genomsnittlig värmeledningsformåga pa 1,75 W/(m • K) och en genomsnittlig termisk dffusivitet på 8.14x10 -7 m2/s.  Numerisk simulering (via COMSOL) utförs för preliminär validering. Jämförelse av experimentella och simuleringsresultat visar avvikelser och en möjlig orsak kan vara: den faktiska värmeinsprutningshastigheten i experimentet är lägre än simulering på grund av värmeförluster i hydraulsystemet; osäkerhet i markens (mättad sand) konduktivitet och termisk diffusivitet.

Given the coinciding growth-trend in the production of consumer electronics and generation of data, the increase in server halls and data centers, as a means for hosting storage capacity for the generated data, has been prominent over the last decades. The establishment of data centers in already existing infrastructure can entail major changes in terms of energy system design. The activity of data processing and storage is power intensive and as the centers demonstrate substantial heat generation, one of the most important fractions of the energy use comes from the need to provide cooling. The study is a techno-economic analysis purposed for determining the feasibility of different cooling systems for a data center in Sweden. The investigated building currently hosts an industrial printing press hall in which paper printing has been conducted for the several decades. This press hall is subject to a refurbishment process to eventually be converted into a data center. In order to achieve the objectives, a data center building model is developed, designated for the estimation of the internal heat generation and demand for cooling. The design and energy requirements of a number of cooling solutions are then investigated and evaluated using a number of performance metrics: Power Usage Effectiveness (PUE), Capital Expenditure (CapEx), Operational Expenditure (OpEx) and Life Cycle Cost (LCC). More specifically the systems incorporate technologies for utilizing air-based free cooling, ground-source free cooling through borehole ground source heat exchangers (GHEs), mechanical cooling through compressor-driven machines as well as District Cooling (DC). The results of the study show that free cooling is a viable solution for covering the vast majority of the yearly cooling requirements, during sufficiently low outdoor temperatures. Free cooling, provided through borehole GHE’s, is feasible as a partial solution from a technical point of view, to provide cooling capacity during warmer periods. However, it can not alone act to provide a major part of the relatively high and constant cooling capacity requirements throughout the year. All of the investigated scenarios display a similar energy performance in terms of total PUE, at values well below the national average of 1.37. It is also seen, that the scenario that displays the lowest LCC includes a combination of free cooling and compressor-driven cooling. This holds for the studied sensitivity cases. It is found that a combined system incorporating borehole GHE’s and compressor cooling machines perform the best in terms of a low PUE. However, the relative difference in energy performance turns out to be lesser than the relative difference in LCC, when substituting the borehole GHE’s for additional cooling machine capacity. / I takt med digitaliseringen och en ökad global användningen- och produktionen av hemelektronik, vilket föranlett en ökad generering av data, har antalet datahallar blivit allt fler de senaste decennierna. Datahallens syfte är att hantera och bereda lagringskapacitet för den data som genereras vilket involverar en rad energikrävande processer. Upprättandet av datahallar i redan befintlig infrastruktur kan medföra förändringar när det kommer till utformningen av byggnadens energisystem. Att bedriva datalagring och informationsbehandling kräver påtagliga mängder elektricitet vilket medför stor intern värmealstring och därtill behov av aktiv kylning.  Denna studie, som valt att benämnas som en tekno-ekonomisk fallstudie, undersöker lämpligheten i implementeringen av olika kylsystem för ett byggnadskomplex i Stockholm. I byggnadens lokaler återfinns idag en industrihall där det sedan flera decennier bedrivits tryckeriverksamhet. Industrihallen är föremål för en konverteringsprocess för att på sikt bli en datahall. Studien är centrerad kring denna konverteringsprocess. För att utvärdera kylbehoven för den framtida datahallen har en modell utvecklats som uppskattar interna värmelaster samt reglerar inomhusklimatet efter rådande krav på inomhuskomfort. Därefter studeras utformning och energibehov för flera olika typer av kylsystemlösningar där en utvärdering av dessa system görs utifrån indikatorerna Power Usage Effectiveness (PUE), Capital Expenditure (CapEx),Operational Expenditure (OpEx) and Life Cycle Cost (LCC). Mer konkret undersöks kombinerade kylsystem som utnyttjar luftburen frikyla, geotermisk frikyla via bergvärmeväxlare (GHEs), mekanisk kyla via kompressordriven kylmaskin samt regional fjärrkyla. Resultaten från studien visar att frikyla från kylmedelskylare är en lämplig lösning för att täcka majoriteten av datahallens kylbehov över ett år, med undantag för årets varmare perioder. Geotermisk frikyla via borrhål är möjlig som partiell lösning ur ett tekniskt perspektiv, men kan inte enskild leverera en majoritet av effekt- eller energibehovet av kyla. Resultatet visar också att alla undersökta scenarier uppvisar en liknande energiprestanda i termer av total PUE, med värden som underskrider det nationella genomsnittet 1,37. Lägst LCC påvisades för ett system som kombinerar luftburen frikyla via kylmedleskylare och mekanisk kyla via kompressordrivna kylmaskiner. Denna låga LCC är signifikant vilket påvisas i utförd känslighetsanalys. Slutligen konstateras att ett system innefattande luftburen och geotermisk frikyla i kombination med kompressordrivna kylmaskiner resulterar i lägst PUE bland de undersökta scenarierna. Den relativa skillnaden i energiprestanda visar sig vara mindre än den relativa skillnaden i LCC, när geotermisk frikyla ersätts med ytterligare kapacitet från kylmaskiner.

The thermal response of a borehole field is often described by non‐dimensional response factors called gfunctions.The g‐function was firstly generated as a numerical solution based on SBM (Superposition BoreholeModel). An analytical approach, the FLS (Finite Line Source), is also accepted for generating the g‐function. In thiswork the potential to numerically produce g‐functions is studied for circular borehole fields using the commercialsoftware COMSOL. The numerical method is flexible and allows the generation of g‐functions for any boreholefield geometry. The approach is partially validated by comparing the solution for a square borehole field containing36 boreholes (6x6) with g‐functions generated with the FLS approach and with the program EED (Earth EnergyDesigner). The latter is based on Eskilsons SBM, one of the first documents where the concept of g‐functions wasintroduced. Once the approach is validated, the square COMSOL model is compared with a circular geometryborehole field developed by the same method, consisting of 3 concentric rings having 6, 12, and 18 boreholes.Finally the influence on the circular geometry g‐function is studied when connecting the boreholes in radial zoneswith different thermal loads. / Den termiska responsen för ett borrhålsfält beskrivs ofta med den dimensionslösa responsfunktionen kallad gfunktion.Responsfunktionen togs först fram som en numerisk lösning med SBM (Superposition Borehole Model).En analytisk metod, FLS (Finite Line Source) är också accepterad för framtagandet av g‐funktioner. I det här arbetetundersöks förutsättningarna att numeriskt ta fram g‐funktioner för cirkulära borrhålsfält genom att använda detkommersiella simuleringsprogrammet COMSOL Multiphysics. Den numeriska metoden är flexibel och kananvändas för alla typer av borrhålsgeometrier. Metoden att använda COMSOL valideras delvis genom att jämföraresultatet för ett kvadratiskt borrhålsfält innehållande 36 borrhål (6x6) med lösningar framtagna med FLS och meddimensioneringsprogrammet EED (Earth Energy Designer). Det senare har sin grund i Eskilsons SBM, ett av deförsta arbeten där begreppet g‐funktion introducerades. När metoden att använda COMSOL verifierats, jämförsden kvadratiska borrhålsmodellen med en cirkulär borrhålskonfiguration, upprättad med samma metod,innehållande 3 koncentriska ringar om vardera 6, 12, 18 borrhål. Slutligen undersöks hur den termiska responsenpåverkas då borrhålen i ett cirkulärt borrhålsfält kopplas samman och grupperas i radiella zoner med olika termiskalaster. / SEEC Scandinavian Energy Efficiency Co.

Tesis por compendio / [ES] El sistema de bomba de calor geotérmica (GSHP) es una tecnología prometedora para utilizar la energía geotérmica somera (EGS). En este sistema, un intercambiador enterrado de calor de perforación (BHE) desempeña un papel principal e influye directamente en el coeficiente de rendimiento estacional (SCOP) de este sistema geotérmico poco profundo. Se han llevado a cabo diferentes estudios para mejorar el rendimiento del BHE, incluyendo el uso de materiales avanzados para el plástico de las tuberías, uso de fluido caloportador (o de transferencia de calor) y de relleno/grouting, de mayor transferencia de calor, diseño de nuevas geometrías, y la optimización del BHE para ser utilizado como sistemas de almacenamiento de energía térmica (BTES). Los costes de perforación, el consumo eléctrico de las bombas de calor y la resistencia térmica de las perforaciones pueden reducirse utilizando materiales con propiedades termofísicas adecuadas, como los nanofluidos y los materiales de almacenamiento térmico. De este modo, no sólo se produce una transferencia de calor más significativa entre el fluido caloportador, el relleno y el terreno, sino que también se reduce el efecto térmico sobre el entorno. El fluido de transferencia de calor es uno de los factores de optimización de la BHE que se utilizará para el almacenamiento de energía térmica (TES). Una mayor conductividad térmica en el fluido de transferencia de calor mejora la eficacia de la transferencia de calor entre el fluido y los materiales alrededor, lo que lleva a alcanzar con mayor rapidez la temperatura de cambio de fase en los materiales de almacenamiento. Cuando se usa un fluido de transferencia de calor con una conductividad térmica superior, la temperatura del material de almacenamiento de calor experimenta fluctuaciones más rápidas, lo que reduce significativamente la duración necesaria para un cambio de fase completo. Además, usar materiales de cambio de fase (PCM) para almacenar calor en lugar del relleno convencional permite aprovechar el BHE como sistema BTES. Además de disminuir considerablemente la profundidad de perforación necesaria, el sistema BTES puede almacenar y liberar energía diaria y estacionalmente para reducir la carga durante las horas punta. Sin embargo, hay un vacío notable en la bibliografía sobre la exploración y aplicación de nuevos materiales de almacenamiento de calor y fluidos de transferencia de calor en las BHE para hacerlas aptas para fines de BTES. Aunque se han aplicado diversas innovaciones para mejorar el rendimiento de los BHE, como el uso de materiales plásticos avanzados y la optimización del diseño, la mayor parte de la investigación se ha centrado en el uso convencional de los BHE. Debería prestarse más atención a las ventajas potenciales del aprovechamiento de los intercambiadores de calor mediante la aplicación de nanofluidos y PCM como fluidos de transferencia de calor y medios de almacenamiento de calor, respectivamente. Como ya se ha mencionado, estos materiales poseen propiedades termofísicas superiores que pueden dar lugar a una transferencia de calor más eficiente, una reducción de los costes de perforación, un menor consumo de electricidad en las bombas de calor y una disminución de la resistencia térmica de la perforación. Esta laguna en la investigación hace necesaria una investigación en profundidad para determinar la viabilidad y factibilidad de la aplicación de estos materiales avanzados en las BHE, facilitando en última instancia su transformación en sistemas BTES fiables. Por lo tanto, los principales objetivos de esta tesis doctoral son estudiar experimental y numéricamente los impactos del uso de materiales avanzados para el fluido caloportador y el relleno/grouting tales como nanofluidos y PCMs, en el rendimiento del BHE como sistemas BTES. El estudio pretende seleccionar los materiales más favorables, convirtiéndose en una referencia práctica y fiable para futuros proyectos y sectores industriales. / [CA] El sistema de bomba de calor geotèrmica (GSHP, en anglès) és una tecnologia prometedora per a utilitzar l'energia geotèrmica succinta (EGS). En este sistema, un bescanviador enterrat de calor de perforació (BHE, en anglès) exercix un paper principal i influïx directament en el coeficient de rendiment estacional (SCOP) d'este sistema geotèrmic poc profund. S'han dut a terme diferents estudis per a millorar el rendiment del *BHE, incloent-hi l'ús de materials avançats per al plàstic de les canonades, ús de fluid termòfor (o de transferència de calor) i de grouting, de major transferència de calor, disseny de noves geometries, i l'optimització del BHE per a ser utilitzat com a sistemes d'emmagatzematge d'energia tèrmica (BTES, en anglès). Els costos de perforació, el consum elèctric de les bombes de calor i la resistència tèrmica de les perforacions poden reduir-se utilitzant materials amb propietats termo-físiques adequades, com els nanofluids i els materials d'emmagatzematge tèrmic. D'esta manera, no sols es produïx una transferència de calor més significativa entre el fluid termòfor, el farciment i el terreny, sinó que també es reduïx l'efecte tèrmic sobre l'entorn. El fluid de transferència de calor és un dels factors d'optimització de la *BHE que s'utilitzarà per a l'emmagatzematge d'energia tèrmica (*TES). Una major conductivitat tèrmica en el fluid de transferència de calor millora l'eficàcia de la transferència de calor entre el fluid i els materials al voltant, la qual cosa porta a aconseguir amb major rapidesa la temperatura de canvi de fase en els materials d'emmagatzematge. Quan s'usa un fluid de transferència de calor amb una conductivitat tèrmica superior, la temperatura del material d'emmagatzematge de calor experimenta fluctuacions més ràpides, la qual cosa reduïx significativament la duració necessària per a un canvi de fase complet. A més, usar materials de canvi de fase (PCM, en anglès) per a emmagatzemar calor en lloc del farciment convencional permet aprofitar el BHE com a sistema BTES. A més de disminuir considerablement la profunditat de perforació necessària, el sistema BTES pot emmagatzemar i alliberar energia diària i estacionalment per a reduir la càrrega durant les hores punta. No obstant això, hi ha un buit notable en la bibliografia sobre l'exploració i aplicació de nous materials d'emmagatzematge de calor i fluids de transferència de calor en les BHE per a fer-les aptes per a fins de BTES. Encara que s'han aplicat diverses innovacions per a millorar el rendiment dels BHE, com l'ús de materials plàstics avançats i l'optimització del disseny, la major part de la investigació s'ha centrat en l'ús convencional dels BHE. Hauria de prestar-se més atenció als avantatges potencials de l'aprofitament dels bescanviadors de calor mitjançant l'aplicació de nanofluids i PCM com a fluids de transferència de calor i mitjans d'emmagatzematge de calor, respectivament. Com ja s'ha esmentat, estos materials posseïxen propietats termo-físiques superiors que poden donar lloc a una transferència de calor més eficient, una reducció dels costos de perforació, un menor consum d'electricitat en les bombes de calor i una disminució de la resistència tèrmica de la perforació. Esta llacuna en la investigació fa necessària una investigació en profunditat per a determinar la viabilitat i factibilitat de l'aplicació d'estos materials avançats en les BHE, facilitant en última instància la seua transformació en sistemes BTES fiables. Per tant, els principals objectius d'esta tesi doctoral són estudiar experimental i numèricament els impactes de l'ús de materials avançats per al fluid termòfor i el grouting com ara nanofluids i PCMs, en el rendiment del BHE com a sistemes BTES. L'estudi pretén seleccionar els materials més favorables, convertint-se en una referència pràctica i fiable per a futurs projectes i sectors industrials. / [EN] Due to severe environmental pollution and worldwide energy deficiency, exploiting renewable energies has become more critical than ever. Shallow geothermal energy (SGE) is considered a sustainable and renewable energy source with significant advantages in space heating and cooling, industrial applications, greenhouses, electricity production, agriculture industry devices, and hot water production, among others. The ground source heat pump (GSHP) system is a promising technology for utilizing SGE. In this system, a borehole heat exchanger (BHE) plays an important role and directly influences the coefficient of performance (COP) of this shallow geothermal system. Different approaches have been carried out to enhance the performance of the BHE, including using advanced materials for pipes, heat transfer fluids, and backfill/grout, designing new geometries, and optimizing the BHE to be used as borehole thermal energy storage (BTES) systems. Drilling costs, heat pump electricity consumption, and borehole thermal resistance can be reduced using materials with appropriate thermo-physical properties like nanofluids and heat storage materials. This results in not only a more significant heat transfer between the heat transfer fluid, the backfill/grout, and the soil but also lessens the thermal effect on the surroundings. Heat transfer fluid is one of the factors in optimizing the BHE to be used for thermal energy storage (TES). Increased thermal conductivity in the heat transfer fluid enhances heat transfer efficiency between the fluid and the heat storage materials, leading to a more rapid attainment of the phase change temperature in the storage materials. In essence, when employing a heat transfer fluid with superior thermal conductivity, the temperature of the heat storage material experiences quicker fluctuations, resulting in a significant reduction in the duration required for a complete phase change. Moreover, the use of phase change material (PCM) as a heat storage medium instead of conventional backfill/grout enables the BHE to be beneficial and applicable as a BTES system. In addition to decreasing the required borehole depth considerably, the BTES system can store and release energy daily and seasonally to reduce the load during peak hours. However, there is a notable gap in the literature concerning exploring and applying new heat storage and heat transfer fluid materials in BHEs to render them suitable for TES purposes. While various approaches have been undertaken to enhance BHE performance, including using advanced materials and design optimizations, most research has concentrated on the conventional goal of BHEs. More attention should be given to the potential advantages of these heat exchangers by applying nanofluids and PCMs as heat transfer fluids and heat storage media, respectively. As mentioned above, these materials possess superior thermo-physical properties that can lead to more efficient heat transfer, reduced drilling costs, lower electricity consumption in heat pumps, and diminished borehole thermal resistance. This research gap necessitates an in-depth investigation to determine the feasibility and practicality of implementing these advanced materials in BHEs, ultimately facilitating their transformation into reliable BTES systems. The outcomes of such research endeavors hold the promise of addressing environmental concerns and global energy deficiencies by advancing the utilization of renewable energy sources like SGE sustainably and effectively. Therefore, the main objectives of this doctoral dissertation are to study experimentally and numerically the impacts of using advanced materials for heat transfer fluid and backfill/grout, such as nanofluids and PCMs, on the performance of the BHE as BTES systems. The study aims to select the most favorable materials, making it a practical and reliable reference for future projects and industry sectors. / This research has received funding from the European Union’s Horizon 2020 Research and Innovation program named GEOCOND under grant agreement No [727583]. / Javadi, H. (2024). Experimental and Numerical Study of the Thermo-Fluid Dynamics of Borehole Heat Exchangers Incorporating Advanced Materials to be Optimized for use as Thermal Energy Storage (BTES) [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/203144 / Compendio

Le suivi de la déformation de la croûte terrestre durant la phase intersismique pour la recherche des transitoires nécessite des instruments précis capables d'opérer pour de très longues durées. Le projet ANR-LINES a visé le développement de trois nouveaux instruments : un sismomètre mono-axial, un inclinomètre hydrostatique à longue base et un inclinomètre de forage pendulaire. Ces trois instruments profitent d'un capteur interférométrique de déplacement à longues fibres optiques du type Fabry-Pérot Extrinsèque (EFFPI). Leurs architectures mécaniques et l'utilisation de longues fibres permettent à ces instruments géophysiques nouvellement fabriqués d'atteindre les objectifs fixés.Le premier objectif de cette étude est de proposer des méthodes adaptées à l'estimation de la phase du chemin optique dans les cavités Fabry-Pérot. Une modulation du courant de la diode laser, suivie par une démodulation homodyne du signal d'interférence et un filtre de Kalman permettent de déterminer la phase en temps réel. Les résultats sont convaincants pour des mesures de courtes durées mais exigent des solutions complémentaires pour se prémunir des effets de la variation des phénomènes environnementaux.Le capteur EFFPI intégré dans l'inclinomètre de forage LINES lui offre l'opportunité d'établir une mesure différentielle de l'oscillation de la masselotte pendulée grâce à trois cavités Fabry-Pérot. Le sismomètre LINES utilise lui aussi le capteur de déplacement EFFPI pour la mesure du déplacement de sa bobine. Une description de l'architecture mécanique de ces instruments et une analyse des phénomènes détectés (mouvements lents, marées, séismes, microséismes . . . ) font partie de cette thèse. / Monitoring crustal deformation during the interseismic phase when searching for earth transients requires precise instruments able to operate for very long periods. The ANR-LINES project aimed to develop three new instruments: a single-axis seismometer, a hydrostatic long base tiltmeter and a borehole pendulum tiltmeter. These three instruments benefit of an extrinsic Fabry-Pérot interferometer (EFFPI) with long optic fibers for displacement detections. Their mechanical architectures and their disposal of long fibers help these newly manufactured geophysical instruments complete their goals.The first objective of this study is to propose appropriate methods for estimating the phase of the optical path in the Fabry-Pérot cavities. A modulation of the laser diode current, followed by a homodyne demodulation of the interference signal and a Kalman filter, allow determining the phase in real time. The results are convincing while taking short periods measurements but require additional solutions for protection against environmental phenomena variations. The EFFPI sensor integrated in the LINES borehole tiltmeter gives it the opportunity to establish a differential measurement of the bob's oscillation thanks to three Fabry-Perot cavities. The LINES seismometer also uses the EFFPI displacement sensor to measure its coil's displacement. A description of the two instruments' mechanical structures and an analysis of the detected phenomena (slow movements, tides, earthquakes, microseisms . . . ) are part of this thesis.Keywords: Laser interferometry, wavelength modulation, synchronous homodyne demodulation, ellipse fitting, Kalman filter, temperature compensation, borehole tiltmeter, simple pendulum, differential measurements, slow drift, seismicobservations, seismometer.