Geothermal heat exchangers are a growing energy technology that improve the energy efficiency of heating and cooling systems in buildings. Vertical borehole heat exchangers (BHE) coupled with ground source heat pumps have been widely developed and researched in the past century. The major disadvantage of BHEs is the initial capital cost required to drill the boreholes. Geothermal energy piles (GEP) were developed to help offset the high initial cost of these systems. A GEP combines ground source heat pump technology with deep earth structural foundations of buildings. GEPs are relatively new technology and robust standards and guidelines have not yet been developed for the design of these systems. The main operational difference between GEPs and conventional BHEs is the length and diameter of the below ground heat exchangers. The diameter of a GEP is much larger and the length is typically shorter than BHEs. Computational fluid dynamics (CFD) analysis is used in this study to investigate and better understand how structural piles perform as geothermal heat exchangers. The CFD analysis is used to simulate an existing experimental energy pile test. The experimental test is modeled as built including fluid modeling to provide additional detail into the behavior of the circulation fluid within the pile. Two comparisons of large diameter GEPs are made using CFD analysis to gain knowledge of the effects of varying pile diameter and loop configuration. The thermal response test was successfully modeled using the CFD model. The CFD results closely match the results of the field test. The large diameter comparisons show that the performance of an energy pile will increase as the diameter increases with a constant loop density. Multiple numbers of loops were tested in a constant diameter pile and the results show that with symmetrically placed loops the performance will increase with a greater number of loops in the pile. / Master of Science

Two different problems of optimization in the utilization of geothermal energy are presented: First, the thermodynamic optimization for a geothermal power plant using a single- or double-flash process is considered; in this analysis, the optimum flash temperature giving the maximum power output is determined. Second, an economic optimization for space heating systems using geothermal energy is developed to obtain operating conditions for which the total (capital and operating) cost is a minimum. Both graphical and analytical methods are used in the thermodynamic optimization to determine the optimum flash temperature. The graphical method is based on thermodynamic data provided by an i-s (enthalpy-entropy) diagram for water and steam, in the analytical method, first and second order approximations (first and second degree polynomial approximations), are used for the functions which express enthalpy differences in terms of flash temperature. Numerical results are provided by computer programs developed for the analytical method. These results cover the temperature range normally encountered in practice. In the case of the single-flash cycle, results from both the graphical and analytical method using the first order approximation indicate the same optimum flash temperature; however, the correction factor resulting from the second order approximation improves the value of the temperature by a correction of about -2 ° C. Optimum flash temperatures for the double-flash cycle are similarly determined using the analytical method with a first order approximation. In the economic optimization of space heating systems, the analysis is made on the basis of the annual total cost per unit area of wall surface. It takes into account the cost of the geothermal fluid, cost of wall insulation, and heat exchanger cost. For a specific case where the inlet temperature to the heat exchanger is at 100° C and the outlet temperature at 28° C, the minimum annual cost to maintain a space at 20°C with an outside temperature of -l0°C is given at $0.0257 per square meter of wall area while the optimum thickness for the wall insulation is 0. 126 meter. Additional improvement in the optimization of flash temperature can be made by using a second order approximation method for the double-flash power cycle.

Despite active volcanism, few geothermal energy resources have been developed in the Cascades Range. Temperature Gradient Hole (TGH) MB 76-31 was drilled to approximately 440 m measured depth to probe for zones where fractures provide fluid conduits that transport deep volcanic heat to shallow depths that could support baseload, carbon neutral electrical generation. These zones were predicted by a Play Fairway assessment (PFA) of resource potential along a zone 11 km west-southwest of the summit of Mount Baker Volcano, Washington State. Rock core, temperature logs, and an acoustic image log were obtained. By comparison to outcrops, the core is interpreted as the Chilliwack Group, comprised of partially metamorphosed basaltic to andesitic volcanics, but due to similar physical and mineral composition may represent the Nooksack Formation. Mapping of core reveals complex, steeply dipping networks of fractures and brecciation along slickensided strike slip faults; clay alteration is common in many of these structures. Most fractures are thoroughly healed by layers of chlorite and calcite, whereas chlorites and vermiculite line open fractures. Fracture porosity is primarily hosted by very dense fractures a few centimeters or less in length. These small fractures are not clearly evident or interpretable in image logs, leading to under-estimated fracture density and secondary porosity, although the image log provides good insights into frequency and attitude of fractures that fully transect the core. The combination of complex, non-planar fracture zones containing many short fractures and healing promote misinterpretation of natural fracture attitude and density in the image log. The equilibrated measured temperature reaches a maximum temperature 32°C at 408 m measured depth along a conductive gradient of 64ºC/km and calculated heat flow of 145 mW/m2 which is more than twice the regional average of 30ºC/km. The presence of vermiculite and several chlorite minerals lining fractures is consistent with the conductive temperature gradient measured in the well below a shallow isothermal zone, although, several fractures are open or only partially healed and resulted in fluid entries into the well. Together, the temperature gradient and vermiculite formation in the fractures indicate local influence of the Mt Baker magmatic system at the Little Park Creek TGH site and that TGH MB 76-31 reaches the upper edge of a caprock above a much deeper hydrothermal system. Do you conclude that this site will/will not support electrical generation? Should have a sentence here describing this since you start your abstract with the idea that you’re testing viability. / Geology

Geothermal energy potential depends on locating highly porous and permeable zones that support fluid flow to extract heat. Hot springs in the playa of Surprise Valley, CA are distributed along gaps and bends in magnetic anomalies interpreted as sub-cropping mafic dikes (Glen et al., 2013). In addition to these dikes in the Valley Playa, dikes outcrop in the Hays Canyon Range (HCR) that defines the eastern margin of the valley. Dikes in the HCR have two distinct attitudes (1) N-S striking dikes (~180) that dip 60oW, and (2) NNW-SSE striking dikes (~330) that dip 85oE. Both attitudes are spatially associated with locally high fracture density and minor hydrothermal alteration that may have formed from dike emplacement. This study tests whether the distribution of hot springs can be explained by elastic distortions around an array of opening dikes that promotes localized dilation to support a network of open secondary structures focusing fluid flow to supply the hot springs. This is done through two mechanical model experiments which use boundary elements in an elastic half-space. The first model is a sensitivity study investigating the role of dike dimensions and position in the density stratigraphy on their opening. Field analysis constrains the strike-length, thickness, and the upper tip position of dikes, although height is unknown. The model reproduced the mapped dike-length (4000 m) and thickness (2.0 m) with a dike-height of 60000m and a magma density of 2500 kg/m3 which is consistent with mafic dikes. The second model applies the dike dimensions and calculates the resulting stress state and fracture potential around an array of dikes conforming to both attitudes of the dike array mapped magnetic anomalies and informed by from field results of dike orientation in the Hays Canyon Range. Simulations of the N-S trend predict regions of enhanced Coulomb stress and tension that promote fracture formation and opening near dike tips where segments are isolated and where two closely spaced dike segments underlap. Conversely, compression is enhanced along the dike walls and where the segments closely overlap. The NNW-SSE trending array of dikes predict increased Coulomb stress and tension at similar locations in the array, but with more extreme values. Thus, the NNW-SSE dike array geometry better matches areas of enhanced fracturing with locations with active hot springs (as well as regions of enhanced compression with their absence) than the geometry of the N-S dike array. / Geology / Accompanied by 3 *.M files: 1)Sawyer_temple_0225M_171/WORKFLOW_p3dResults_Sensitivity_positionbc_interrogation_3d_NCD.m 2)Sawyer_temple_0225M_171/WORKFLOW_p3dResults_Sensitivity_positionbc_figures.m 3)Sawyer_temple_0225M_171/WORKFLOW_p3d_SV_toy_dikes_Sensitivity_positionbc.m

M. S.

No description available.

Energy extraction from dry geothermal sources (subterranean hot rock), and subsequent conversion to electrical power was analyzed. Analytical closed form solutions of the governing heat conduction equation were used to predict electrical power levels and total outputs. Four subterranean reservoir geometries were considered. A semi-infinite planar crack was ued as a first approximation to the fissure geometry created by hydraulic fracturing of a well in which no subsequent fracture growth occurs. The initial model was later refined using a finite disk to model the fracture geometry. A finite thickness slab, infinite in extent, was used to approximate the fissure geometry created by thermal stress cracking in a hydraulically fractured well. The fourth geometry modeled a cylindrical well bore. In the analyses, heat transfer in the rock and the thermal efficiency of a heat engine were considered in determining the amount of electrical power which could be generated from geothermal energy. For a fracture 1 Km in diameter operating at an optimum heat flux, with an initial rock temperature of 600 K (620 F), and a surface ambient temperature (condenser temperature) of 310 K (100 F), it was calculated that a total of 1.75 million Mw-hrs of electricity could be generated over a 30 year period at a continuous rate of not less than 5 Mw. / M.S.

<p>The aim of this report was to do a case study at a geothermal heating system which has been in operation for about 5 years, and study if its performance has changed during this period of time. A literature study about the processes involved was also done in purpose of background knowledge.</p><p>The tenant-owner’s association Duvan at Petterslundsgatan in Uppsala installed year 1999-2000 a geothermal heating system. The purpose of this installation was that they hoped it would lead to a smaller usage of district heating which would lead to a reduction of the heating expenses for their buildings. The geothermal heating system consists of 19 energy wells and 4 geothermal heat pumps, and it is one of the first systems of that size in the region of Uppsala. Due to that, the system at Duvan is referred to as a reference project for geothermal heating system of this size. The reason that the study was made after 5 years is that it takes about 5 years before the heat equilibrium in the bedrock has been stabilized after a geothermal heat system has been installed. The temperature in the bedrock will decrease during this 5 year period and the performance of the system will change.</p><p>In this report factors such as geology, groundwater levels and temperature changes are examined to get a summery of the processes that extract heat from the bedrock and convert it to conventional energy. Data from the compressors has been examined, energy usage before and after the installation of the system has been compared and finally an economical calculation of the tenant-owner’s association energy consumption has been made. All the main points in this report point to the fact that the system is working properly and that it has contributed to an economical benefit regarding to the energy usage.</p> / <p>Syftet med detta examensarbete var att göra en fallstudie på ett befintligt bergvärmesystem som har varit i drift i 5 år, och studera om dess prestanda har förändrats under den tid som systemet använts. Som bakgrund genomfördes även en litteraturstudie över de processer som äger rum då geotermisk energi kan utvinnas samt hur denna energi konverteras till konventionell energi för uppvärmning av lokaler.</p><p>Bostadsrättsföreningen Duvan på Petterslundsgatan i Uppsala installerade under år 1999-2000 ett bergvärmesystem som skulle leda till ett mindre användande av fjärrvärme och således bidra till att utgifterna för inköp av energi skulle minska. Systemet består av 19 energibrunnar och 4 värmepumpar, och är en av de första anläggningarna av denna storlek i Uppsala regionen. Detta gör att Bostadsrättsföreningen Duvan ses som ett referensobjekt för anläggningar av denna storlek. Anledningen till att studien gjordes vid denna tidpunkt var att det tar ungefär 5 år innan värmebalansen i berggrunden stabiliseras när ett bergvärmesystem installeras, och temperaturen i berggrunden kommer under denna period minska vilket leder till prestandaförändringar hos värmepumpen. Denna femårsperiod har nu gått och en relevant undersökning av systemet har kunnat göras.</p><p>I denna rapport beskrivs bakomliggande parametrar så som geologi, grundvattennivåer och temperaturförändringar som behövs för att få en överblick över situationen och kunna ge en inblick i vad som påverkar utvinningen av energi i berggrunden. Data från kompressorernas drifttider och förbrukning av energi före och efter installationen av bergvärmesystemet jämförs och slutligen görs en ekonomisk kalkyl för bostadsrättsföreningens energiförbrukning. Alla de punkter som rapporten undersöker visar att systemet fungerar väl och att det bidragit till en ekonomisk vinst med avseende på energianvändandet.</p>

Mr Wayne Tobeck, Director of Southrim Group (SRG), sponsored this 2013 MEM Project titled; A Technical and Economic Feasibility Study for the Integration of GSHP Technology in the Christchurch Rebuild. Following the recent Christchurch earthquakes, a significant amount of land has become too unstable to support traditional building foundations. This creates an opportunity to implement new and unique foundation designs previously unconsidered due to high costs compared to traditional methods. One such design proposes that an Injection Micro-Piling technique could be used. This can also be coupled with HVAC technology to create a Ground Source Heat Pump (GSHP) arrangement in both new buildings and as retrofits for building requiring foundation repair. The purpose of this study was to complete a feasibility study on the merits of SRG pursuing this proposed product. A significant market for such a product was found to exist, while the product was also found to be technically and legally feasible. However, the proposed product was found to not be economically feasible with respect to Air Source Heat Pumps due to the significantly higher capital and installation costs required. Further analysis suggests GSHPs may become more economically attractive in operating temperatures lower than -9oC, though the existence of markets with this climate in NZ has not been studied. It is therefore suggested that SRG do not proceed with plans to develop a GSHP coupled foundation solution for the Christchurch rebuild.

In this thesis, the potential of enhanced geothermal system to provide adequate energy to a 10 MW electricity power plant from Prairie Evaporite Formation of Williston Basin was investigated. This formation partly consists of halite with low thermal resistance and high thermal conductivity, which translates into a lower drilling length to reach the desired temperature, comparing to other rock types. To this end, two numerical models with experimental data in south-west Manitoba (i.e. Tilston) and south-east Saskatchewan (i.e. Generic) were designed. The thermal reservoirs were located at 1.5 km (Tilston site) and 3 km (Generic site) with approximate thicknesses of 118 m. Considering an injection brine of 6% NaCl at 15°C, the final derived temperature at wellhead of the production wells were 43°C and 105°C respectively. Finally, the Generic site was concluded as a suitable candidate for electricity production by providing higher surfaced fluid temperature than the minimum of 80°C. / February 2017