Žemės šilumos siurblių sistemos surenka žemės šilumą, dažniausiai vertikaliu U formos gręžinio šilumokaičiu. U formos gręžinio šilumokaičio našumas priklauso nuo šiluminių žemės savybių, taip pat nuo gręžinyje naudojamo skiedinio ar užpildo. Siekiant, kad Žemės šilumos siurblių sistemos pasiteisintų, projektuojant reikia atsižvelgti į geologinių struktūrų šiluminį laidumą ir gręžinio šilumokaičio šiluminę varžą. Šio darbo tikslas buvo nustatyti šilumos siurblio, naudojančio grunto šilumą, pritaikymo individualioje sodyboje siurblio techninis ir ekonominis įvertinimas. Nustatyta, kad investicijos projektui įgyvendinti, kai gyvenamajam pastatui šildyti ir buitiniam karštam vandeniui ruošti šildymo sezono metu šilumą gamina šilumos siurblys, naudojantis grunto šilumą, palyginti su tiesioginiu elektros naudojimu pastatui šildyti ir buitiniam karštam vandeniui ruošti, atsiperka per 6,3 metus. Šiluminės reakcijos testas padeda nustatyti šiluminį žemės laidumą (λ) gręžinio šilumokaičio įrengimo vietoje, bei efektyvią gręžinio šilumokaičio šiluminę varžą (Rb). Pagrindinis tikslas buvo suderinti gręžinio šilumokaitį su žemės sąlygomis, taip pat nustatyti gręžinio gylio poveikį (60 m: VB2; 90 m: VB3). / Ground source heat pump systems exchange heat with the ground, often through a vertical, U-tube, borehole heat exchanger. The performance of this U-tube borehole heat exchanger depends on the thermal properties of the ground formation, as well as grout or backfill in the borehole. The design and economic probability of ground source heat pump systems need the thermal conductivity of geological structure and thermal resistance of borehole heat exchanger. An economic and technical evaluation of the heat pump, which is using ground heat, in individual homestead. It was found that the investment for this project, when heat pump using ground heat is used to heat residential building and domestic hot water in heating season, compared with the use of direct electric heating of buildings and domestic hot water payback within 6.3 years. Thermal response test method allows the in-situ determination of the thermal conductivity (l) of the ground formation in the vicinity of a borehole heat exchanger, as well as the effective thermal resistance (Rb) of this latter. The main goal has been to determine same in-situ ground type of borehole heat exchanger, including the effect of borehole’s depths (60 m: VB2; 90 m: VB3).

In 2009 Ball State University began construction on the nation’s largest ground-source geothermal system in attempt to reduce its environmental impacts and heating/cooling expenses. Since late November 2011, half of the geothermal system has been operational. Due to only partial geothermal use and a warm winter in 2011, thermal increases can be seen throughout the Phase 1 fields. After system initiation in 2011, an average temperature increase of 4.33°C has been observed in the bottom 80-120+ meters in the middle of the South Field, while no increase was found in the southern-edge well of the North Field. To evaluate thermal increases, hydraulic characteristics were gathered including groundwater flow direction, hydraulic gradients and hydraulic conductivities. Varying temperatures throughout the area may affect the groundwater geochemistry. Geochemical results indicate a calcium-bicarbonate facies. / Geothermal well field construction -- Study site -- Methods -- Results -- Discussion. / Department of Geological Sciences

An investigation was conducted to determine the response of landfills to the operation of a vertical ground source heat pump (i.e., heat extraction system, HES). Elevated landfill temperatures, reported various researchers, impact the engineering performance of landfill systems. A numerical model was developed to analyze the influence of vertical HES operation on landfills as a function of climate and operational conditions. A 1-D model of the vertical profile of a landfill was developed to approximate fluid temperatures in the HES. A 2-D model was then analyzed over a 40 year time period using the approximate fluid temperatures to determine the heat flux applied by the HES and resulting landfill temperatures. Vertical HES configurations simulations consisted of 15 simulations varying 5 fluid velocities and 3 pipe sizes. Operational simulations consisted of 26 parametric evaluations of waste placement, waste height, waste filling rate, vertical landfill expansions, HES placement time, climate, and waste heating. Vertical HES operation in a landfill environment was determined to have 3 phases: heat extraction phase, transitional phase, and ground source heat pump phase. During the heat extraction phase, the heat extraction rate ranged from 0 to 2550, 310 to 3080, and 0 to 530 W for the first year, peak year, and last year of HES operation, respectively. The maximum total heat energy extracted during the heat extraction phase ranged from 163,000 to 1,400,000 MJ. The maximum difference in baseline landfill temperatures and temperatures 0 m away from the HES ranged from 5.2 to 43.2°C. Climate was determined to be the most significant factor impacting the vertical HES. Trends pertaining to performance of numerous variables (fluid velocity, pipe size, waste placement, waste height, waste filling rate, vertical landfill expansions, HES placement time, climate, and waste heating) were determined during this investigation. Increasing fluid velocity until turbulent flow was reached increased the heat extraction rate by the system. Once turbulent flow was reached, the increase in heat extraction rate with increasing fluid velocity was negligible. An increase in the heat extraction rate was caused by increasing pipe diameter. Wastes placed in warmer months caused an increase in the total heat energy extracted. Increasing waste height caused an increase in the peak heat extraction rate by 43 W/m waste height. Optimum heat extraction per 1 m of HES occurred for a 30 m waste height. Increasing the waste filling rate increased the total heat energy extracted. Heat extraction rates decreased as time between vertical landfill expansions increase. Total heat energy extracted over a 35 year period decreased by approximately 21,500 MJ/year for every year after the final cover was placed until HES operation began. For seasonal HES operation, the total heat energy obtained each year differs and the fourth year of operation yielded the most energy. Wet Climates with higher heat generating capacities yielded increased heat extraction rates. Maximum temperature differences in the landfill due to the HES increased by 16.6°C for every 1 W/m3 increase in peak heat generation rate. When a vertical HES was used for waste heating, up to a 13.7% increase in methane production was predicted. Engineering considerations (spacing, financial impact, and effect on gas production) for implementing a vertical HES in a landfill were investigated. Spacing requirements between the wells were dependent on maximum temperature differences in the landfill. Spacing requirements of 12, 12, 16, and 22 m are recommended for waste heating, winter-only HES operation, maximum temperature differences in the landfill less than 17°C, and maximum temperature differences in the landfill greater than 17°C, respectively. A financial analysis was conducted on the cost of implementing a single vertical HES well. The energy extracted per cost ranged from 0.227 to 0.150 $/MJ for a 50.8 mm pipe with a 1.0 m/s fluid velocity and a 50.8 mm pipe with a 0.3 m/s fluid velocity, respectively. A vertical HES could potentially increase revenue from a typical landfill gas energy project by $577,000 per year.

Nowadays Ground Source Heat Pumps (GSHP) are widely used to provide heating and/or cooling as well as domestic hot water in commercial and residential buildings. The Swedish GSHPs market is the first one in the European Union with more than 378,000 units installed until 2010 according to the Swedish Heat Pump Association (SVEP). This thesis focuses on the improvement of a Thermal Response Test (TRT) apparatus available at KTH Royal Institute of Technology – Energy Technology Department. This equipment aims at improving Borehole Heat Exchanger (BHE) design in terms of size. Its key purpose is to evaluate two main BHE properties: the ground thermal conductivity and the borehole thermal resistance. A new command software is developed in order to control the TRT equipment and run TRT measurements. This new software is developed using Python as programming language and replaces an older program which needed LabVIEW to run. The TRT command software designed in this thesis provides the user with a simple and user-friendly interface to control each device of the equipment. Measurements are exported and saved to files which can be open with both Microsoft Excel and the analysis tool also developed in this thesis. The stand-alone evaluation tool can be used to analyse TRT and/or DTRT measurements. This analysis tool helps the user to compute large amount of data with few data manipulation and low computation time. Model parameters and TRT/DTRT measurement can be imported from files into it and different fitting settings are available to run the optimization, i.e. account for baseline variations (early activities in the borehole, different optimization periods, analysis during thermal recovery of the ground, single/multi-sectional analysis along the depth, among others). This report covers a theoretical description of TRT experiments and its models, the objectives of such a project and the development of the control and evaluation tools.

Solar photovoltaic-thermal (PVT) modules produce heat and power via a heat exchanger attached to the rear of the PV cells. The novel PVT collector in this study is previously untested and therefore its behaviour and thermo-electric performance due to fluid channel configuration and in various climate and operating conditions are unknown. Moreover, the working fluid flowing through the heat exchanger cause a temperature gradient across the module such that a cell near the inlet and a cell near the outlet may have significant temperature differences. PV cells are sensitive to temperature; however the most common way to simulate power output from a PVT is to use the average temperature and ignore the gradient. In this study, a single diode PV model is incorporated into a commercial thermal solver to co-simulate the thermal and electrical output of a novel PVT module design with cell level resolution. The PVT system is modelled in steady state under various wind speeds, inlet temperatures, ambient temperatures, flow rates, irradiation, convection coefficients from coolant and back of the module and two different fluid channel configurations. The results show that of the controllable variables, the inlet temperature has the highest influence of the total power output and that a parallel flow of the fluid channel configuration is preferable. The difference between the cell resolution and the module resolution simulations do not motivate the use of a higher resolution numerical simulation. / En kombinerad solcellspanel och solvärmefångare (PVT) producerar värme och elenergi på samma yta genom att en värmeväxlare upptar värmen från baksidan av solcellspanelen. Den PVT som berörs i denna studien är nyutvecklad och har aldrig tidigare testats, vilket medför att data för hur den beter sig samt dess termo-elektiska prestanda saknas för olika driftförhållanden samt flödeskonfigurationer. Vidare ger mediet som flödar genom värmeväxlaren upphov till en temperaturgradient, vilken kan innebära en påtaglig skillnad i temperatur mellan solcellerna i solcellspanelen vid mediets in- respektive utlopp. Trots solcellers temperaturkänslighet, så sker simulering i allmänhet med avseende på panelens medeltemperatur istället för att hänsyn tas till denna temperaturgradient. I den här studien implementeras en så kallad  ”single diode”-modell i en kommersiell numerisk mjukvara termiska beräkningar för att samsimulera termiskt och elektriskt effektuttag ur den nyutvecklade PVT-designen. Designen modelleras statiskt under givna variationer av vindhastighet, inloppstemperatur, omgivande temperatur, flödeshastighet, solinstrålning och konvektionskoefficienter för mediet samt baksidan av modulen. Resultaten visar att kontrollerbara variabler som inloppstemperatur har högst inverkan på den totala effekten samt att en parallell flödeskonfiguration lämpar sig bäst. Studien visar också att skillnaden mellan simulering på cellnivå och modulnivå inte motiverar en numerisk beräkningsmetod med upplösning satt till solcellsnivå.

A ground source heat pump (GSHP) system utilizes a borehole heat exchanger to extract energy from the ground during the heating season and to deposit energy during the cooling season. This requires the drilling of an extended borehole, typically ranging from 100 to 200 meters in length, with a diameter of approximately 6 to 8 inches. Inside the borehole, a U-shaped tube is placed and surrounded by a grout that aids heat transfer between the tube and the surrounding soil. A heat transfer fluid, often a mixture of water and glycol, circulates through the tube to exchange heat with the ground. During the winter, the system draws energy from the ground for household space heating, while in the summer, when air conditioning is used, it expels energy from the house into the ground. In regions with heating-dominated climates, such as Canada, more energy is withdrawn from the ground during the winter than can be naturally restored during the summer. Consequently, the soil progressively cools over time, leading to reduced heat pump coefficient of performance and a decline in the overall system efficiency. This study explores a solution to this issue by integrating solar domestic hot water systems which employ solar thermal collectors to heat water for domestic purposes. These systems are relatively straightforward, consisting of solar thermal collectors, piping, pumps, a hot water tank, and controllers. The collector area is designed to deliver high solar fractions during the summer, but it typically exhibits lower efficiency in the winter. In Toronto, annual solar fraction, defined as the proportion of energy supplied by the solar thermal system to the total energy required by the load, typically range between 50-70%. This research aims to leverage solar thermal collectors for recharging the ground during the summer months. This approach enables the installation of larger collector areas, improving system performance in the winter, while simultaneously depositing excess energy into the ground during the summer. Notably, this study focuses on a single household located in Toronto, Canada, where the recommended solar thermal collector area is 10 square meters, and the borehole heat exchanger length is 150 meters. Also, it is assumed that four people are living in this house and required energy for heating and cooling of the house are 28000 and 7000 kWh per year, respectively. This approach offers a promising solution to balance seasonal heat transfer to the ground, mitigating the long-term decline in GSHP performance. The study demonstrates that by coupling the solar thermal system with the GSHP, the targeted outcomes are achievable. / Thesis / Master of Applied Science (MASc)

Yes / The performance of Ground Source Heat Pump (GSHP) systems for domestic use is an increasing area of study in the UK. This paper examines the thermal performance of three bespoke shallow horizontal GSHP systems installed in newly built residential houses in the North of England against a control house which was fitted with a standard gas boiler. A total of 350 metres of High Density Polyethylene pipe with an external diameter of 40 mm was used for each house as a heat pump loop. The study investigated (i) the performance of a single loop horizontal Ground Heat Exchanger (GHE) against a double loop GHE and (ii) rainfall effects on heat extraction by comparing a system with an infiltration trench connected to roof drainage against a system without an infiltration trench above the ground loops. Parameters monitored for a full year from October 2013 to September 2014. Using the double GHE has shown an enhanced performance of up to 20% compared with single GHE. The infiltration trench is found to improve performance of the heat pumps; the double loop GHE system with an infiltration trench had a COP 5% higher than that of the double loop GHE system without a trench.

The borehole heat exchangers of today suffer from poor thermal and hydrodynamic performance. The purpose of this thesis is to improve the performance of ground source heat pump systems and thermal energy storages by increasing the energy efficiency of the borehole heat exchangers. For this reason, the annular coaxial borehole heat exchanger (CBHE) has been analyzed. This type of heat exchanger is interesting in terms of both thermal and hydrodynamic performance. A model has been set up in the program Comsol Multiphysics in order to investigate the heat transfer characteristics along the borehole. A literature survey that summarizes the analytical calculation methods developed in earlier Swedish research is presented in the report. Different geometries with or without insulation of the central pipe have been analyzed and the effective borehole resistance for each geometry has been calculated based on the simulation results. The model has been validated against a recently performed thermal response test, and shows very good correlation with reality. The results from the simulations show that by using the annular CBHE an increase of 2-3 °C in the evaporator of the heat pump can be achieved. Calculations show that the pump work (head loss) can be reduced to 1/6 of the corresponding case with a single U-pipe. There arises a vertical temperature gradient in the bedrock when recharging and extracting heat with the annular CBHE. This means that the annular CBHE acts like a counter-flow heat exchanger which is thermally optimal. In total, the simulation result shows that the annular CBHE geometry in this thesis can increase a system's seasonal performance factor (SPF) with 10-19 % in comparison with a U-pipe BHE. This is equivalent to 10-19 % lower electrical power consumption every year.

The ground source resources are becoming more and more popular and now the ground source heat pumps are frequently used for heating and cooling different types of buildings. This thesis aims at giving a contribution in the development of the thermal modelling of borehole heat storage systems. Furthermore, its objective is to investigate the possibility of implementing of a GSHP (ground source heat pump) with vertical boreholes, in order to deliver the heating and cooling demand for a passive house and to emphasize some certain advantages of this equipment even in the case of a small building (e.g. residential house). A case study is presented to a suitable modelling tool for the estimation of the thermal behaviour of these systems GSHP by combining the outcome from different modelling programs. In order to do that, a very efficient residential solar house (EFden House – a passive residential single-family house, which was projected and built in Bucharest with academic purposes) is being analysed. The numerical results are produced using the software DesignBuilder, EED (Earth Energy Designer) and a sizing method for the length of the boreholes (ASHRAE method). The idea of using 2 different modelling programs and another sizing method for the borehole heat exchanger design (ASHRAE method) is to make sure that all the calculations and results are valid and reliable when analysing such a system theoretically (in the first phases of implementing a project), before performing a geotechnical study or a thermal response test in order to assess the feasibility of such a project beforehand. The results highlight that the length of the borehole, which is the main design parameter and also a good index in estimating the cost of the system, is directly influenced by the other fundamental variables like thermal conductivity of the grout, of the soil and the heat carrier fluid. Also, some correlations between these parameters and the COP (coefficient of performance) of the system were made. The idea of sizing the length of boreholes using two different methods shows the reliability of the modelling tool. The results showed a difference of only 2.5%.  Moreover, the length of borehole is very important as it was calculated that can trigger a difference in electricity consumption of the GSHP up to 28%. It also showed the fact that the design of the whole system can be done beforehand just using modelling tools, without performing tests in-situ. The method aims at being considered as an efficient tool to estimate the length of the borehole of a GSHP system using several modelling tools. / <p>The presentation was made via Skype due to the programme being online based</p>

In the context of energy transition, geothermics play an important role for the heating and cooling supply of both residential and commercial buildings. Thereby, the increasingly and intensive utilisation of shallow geothermal resources bears the risk of over-exploitation and thus poses a future challenge to ensure the sustainability and safety of such systems. Particularly, the well-established technology of borehole heat exchanger-coupled ground source heat pumps is applied for the thermal exploitation of the shallow subsurface. Due to the complexity of the involved physical processes, numerical modelling proves to be a powerful tool to enhance process understanding as well as to aid the planning and design processes. Simulations can also support the management of thermal subsurface resources, planning and decision-making on city and regional scales. In this work, the so-called dual-continuum approach was adopted and enhanced to develop a coupled numerical model considering flow and heat transport processes in both the subsurface and borehole heat exchangers as well as the heat pumps’ performance characteristics, and including the relevant phenomena influencing the underlying processes. Beside the temperature fields, the efficiency and thus the consumption of electrical energy by the heat pump is computed, allowing for the quantification of operational costs and equivalent carbon-dioxide emissions. The model is validated and applied to a number of numerical studies. First, a comprehensive sensitivity analysis on the efficiency and sustainability of such systems is performed. Second, a method for the quantification of technically extractable shallow geothermal energy is proposed. This procedure is demonstrated by means of a case study for the city of Cologne, Germany and its implications are discussed. / Im Rahmen der Energiewende nimmt die Geothermie eine besondere Rolle in der thermische Gebäudeversorgung ein. Die zunehmende, intensive Nutzung oberflächennaher geothermischer Ressourcen erhöht die Gefahr der übermäßigen thermischen Ausbeutung des Untergrundes und stellt damit eine wachsende Herausforderung für die Nachhaltigkeit und Sicherheit solcher Systeme dar. Zur Erschließung oberflächennaher geothermischer Energie wird insbesondere die etablierte Technologie Erdwärmesonden-gekoppelter Wärmepumpen eingesetzt. Aufgrund der daran beteiligten komplexen physikalischen Prozesse erweisen sich numerische Modelle als leistungsfähiges Werkzeug zur Erweiterung des Prozessverständnisses und Unterstützung des Planungs- und Auslegungsprozesses. Zudem können Simulationen zum Management thermischer Ressourcen im Untergrund sowie zur Planung und politischen Entscheidungsfindung auf städtischen und regionalen Maßstäben beitragen. Im Rahmen dieser Arbeit wurde, basierend auf dem sogenannten ”dual-continuum approach” und unter Berücksichtigung des Einflusses der Wärmepumpe, ein erweitertes gekoppeltes numerisches Modell zur Abbildung der in Erdwärmesonden und dem Untergrund stattfindenden Strömungs- und Wärmetransportprozesse entwickelt. Das Modell ist in der Lage, alle relevanten Einflussfaktoren zu berücksichtigen. Neben den Temperaturfeldern im Untergrund und der Erdwärmesonde werden die Effizienz und damit der Stromverbrauch der Wärmepumpe simuliert. Damit können sowohl die Betriebskosten als auch der äquivalente CO 2 -Ausstoß abgeschätzt werden. Das Modell wurde validiert und in einer Reihe numerischer Studien eingesetzt. Zuerst wurde eine umfassende Sensitivitätsanalyse zur Effizienz und Nachhaltigkeit entsprechender Anlagen durchgeführt. Weiterhin wird ein Verfahren zur Quantifizierung des technisch nutzbaren, oberflächennahen geothermischen Potentials vorgestellt und anhand einer Fallstudie für die Stadt Köln demonstriert, gefolgt von einer Diskussion der Ergebnisse.