This thesis analyses long term and short term environmental effects on geothermal power plant performance and discusses adaptive ways to improve performance. Mokai 1 geothermal power plant has been used as a case study for this investigation. Mokai 1 is a combined cycle plant where the binary cycles are air-cooled. The plant performance of an air-cooled binary cycle geothermal power plant is dependent on the environment (resource characteristics as well as weather conditions). For modelling such a power plant, two time scales are of interest: the yearly basis for aggregate plant performance for design and operations; and the daily basis for hourly plant performances for an accurate dispatch prediction. Adaptive methodology for long term performance improvement has been introduced in this work which would save money and effort in the future by keeping the provisions to adapt to changes in resource characteristics based on geothermal reservoir modelling. The investigation was carried out using a steady state computer simulator of Mokai 1 geothermal power plant. The steady sate simulator was built specifically for this work. The deviation in performance of various components is less than 5% compared to the original plant design. The model is very generic and it can be used for other plants with simple adaptation or can be used for future plant design. One of the main contributions of this work is an iterative method for modelling the environmental effect on short term performance on the air-cooled organic Rankine cycle. The ambient temperature is identified as the most influencing parameter on short term performance which influences the performance of the whole cycle in two ways. Firstly, by changing the equilibrium pressure inside the condenser, the turbine outlet pressure changes and hence, the turbine pressure ratio also changes. The turbine pressure ratio is a major parameter determining power generated by a turbine; therefore, the plant output is affected. Secondly, by changing the condenser outlet temperature with the ambient temperature, the pump inlet and outlet condition and consequently vaporizer equilibrium temperature and pressure are influenced. The developed method sought the equilibrium conditions of both condenser and vaporizer iteratively. In short, ORC cycle shifts on the T-s plane depending on the ambient temperature. This method iteratively seeks the shifted ORC on the T,s plane. Two case studies have been carried out to demonstrate the method. The developed method shows robustness and converges exponentially. The model is effective for cycles that use saturated vapour as well as superheated vapour. The model essentially assumes steady state operation of the power cycle. The possible unit time where this model can be applied is bounded by the time required by a system to come into steady state. The saturated vapour cycle yielded average error 4.20% with maximum error 9.25% and the superheated vapour cycle yielded average error 2.12% with maximum error 5.60%. The main advantage of the developed method is that it requires a minimum number of inputs: condenser (p,T), vaporizer (p,T), condenser heat load, turbine efficiency (overall), pump work and the extremum conditions of all the components. These inputs should represent typical operating conditions of a plant. The model can predict the appropriate plant performance depending on the system heat input (geothermal fluid flow in this case) and the heat sink temperature. As the method is based on basic thermodynamics rather than empirical or semi-empirical approaches, this method is widely applicable. The main focus of this work is on the ORC but the developed method is applicable to any closed Rankine cycle. In addition, application of the developed iterative method to predict plant performance based on mean yearly weather data is also discussed in the thesis. Water-augmented cooling system and optimization of plant operating point parameters have been proposed as adaptive measures to improve short term performance. Developed iterative method has been used for the short term performance analysis. The water-augmented cooling system is specifically suitable to mitigate the reduced power output during the summer. The simulated average gain in power during the summer (Jan, Feb, Nov and Dec) of an ORC of Mokai 1 geothermal power plant by incorporating a water-augmented cooling system was 2.3% and the average gain for the whole year was 1.6% based on the weather data of Taupo for the year 2005. A cost benefit analysis showed that water-augmented cooling system is more economical compared to other alternative renewable energies considered to meet summer peak demand. From the green house gas emissions perspective, water-augmented cooling is a better option than the gas fired peaking plants. Adaptive approach for short term performance improvement by optimizing operating point parameters of an air-cooled binary cycle has huge potential with possible maximum improvement in power output by about 50%. The optimization takes in to account the effects of the geothermal resource characteristics and the weather conditions. The optimization is achieved by manipulating cycle mass flow rate and vaporizer equilibrium condition. Further study on the optimizing operating points to achieve improved short term performance has been recommended for future work.

This thesis examines the energy return on investment (EROI) of a model 3 MW hybrid gas-geothermal plant on the Texas Gulf Coast. The model plant uses a design similar to the DOE Pleasant Bayou No. 2 test geothermal plant, and uses a gas engine to harness entrained methane and an Organic Rankine Cycle turbine to harness thermal energy from hot brines. The indirect energy cost was calculated using the Carnegie Mellon University Economic Input-Output Life Environmental Life Cycle Analysis (EIO-LCA) model. The EROI of the plant using the 1997 EIO-LCA energy data is 12.40, and the EROI of the plant using 2002 EIO-LCA energy data is 14.18. Sensitivity analysis was run to determine how the plant parameters affect the EROI. A literature review of the EROI of different power sources shows that the EROI of the hybrid geothermal plant is greater than the EROI of flash steam geothermal and solar, but is lower than the EROI of dry steam geothermal, wind power, nuclear, coal, gas, and hydroelectric plants. An analysis of the EROI to financial return on investment (FROI) shows that the FROI for a hybrid geothermal plant could be competitive with wind and solar as a viable renewable resource in the Texas electricity market. / text

Although there is no obvious reason why seismic 6-value and the spatial fractal dimension of earthquakes, D, should be related, there are several reports of observed empirical correlations between these two quantities. In order to investigate this phenomenon, and attempt to relate it to different types of earthquakes, industrially induced seismicity in The Geysers geothermal area, California and earthquake swarms in Long Valley caldera, California were analysed. Raw seismograms from the Unocal-NEC-Thermal network in The Geysers were processed automatically, calculating magnitudes from coda lengths and locating them using a three-dimensional velocity model. Seismicity correlated with the locations of commercial wells and surface fault locations. The entire Geysers dataset was too complex for clear correlations between b, D, seismicity and injection to be observed. In several cases, short pulses of injection induced bursts of seismicity of either small-magnitude, clustered events or large-magnitude diffuse seismicity, resulting always in a transient anomaly of negative b/D. However, sometimes pulses of injection were not accompanied by b/D transients and sometimes b/D transients were not accompanied by known injection. The latter cases may or may not indicate undisclosed injection activity. A seismic crisis in Long Valley caldera was associated with major b/D anomalies that accompanied migration of the activity from a hydrothermal zone on the south edge of the resurgent dome to the right-lateral, blind, near-vertical South Moat fault to the immediate south. The results indicated that the hydrothermal zone is an inhomogeneous structure whereas the South Moat has a mature, coherent fault plane, capable of generating magnitude M = 6 earthquakes and posing a threat to the town of Mammoth Lakes.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Not available / text

The hydro-mechanical effects of high pressure fluid injections into jointed rock are considered mostly in the context of Hot Dry Rock (HDR) geothermal energy systems. In Part I, the mai n aspects ari sing from the HDR research at the "Camborne School of Mines (CSM) and Los Alamos Nat iana 1 Laboratory (LANL) projects are reviewed. Previous approaches to fluid-rock interacti ons at these projects and important observed phenomena are highlighted. Fundamental aspects of rock joint geometry, mechanical behaviour and flow regimes within jointed rock are also reviewed. These aspects are then related to possible conditions in HDR systems. The role of in situ stress conditions is of great significance in this study and is reviewed theoretically and in detail for both the CSM and LANL project sites. The revi ew incl udes a comprehensi ve seri es of measurements, by different techniques, organised and interpreted by the author at the CSM project. In Part II, model development, the emphasis is on intermediate fluid pressures which are too high for simple diffusion alone and too low for tensile hydraulic fracturing. The dominant mechanical activity is one of joint shear. Strike-slip shearing due to fluid injection is examined in two dimensions with the numerical model FRIP, which has been extended by the author. Similar behaviour is examined in three dimensions with an analytical model which is linked to microseismic observations. This model explains the observed phenomenon of downward shear growth. Joint distribution and mechanical properties, and their effect on fluid diffusivity, are examined and used in analytical models of fluid pressure pulse propagation, tracer transport, and rock stress increment transfer. All models are used to help interpret field data, mainly from the CSM project. The models are also of potential application to hydrocarbon reservoir stimulation, liquid waste disposal and leakage from high pressure water tunnels.

No description available.

Organic petrology and RockEval-TOC pyrolysis studies were carried out on over 600 samples of shales, siltstones, marls and coals from forty three sections in the Upper Devonian and Carboniferous strata of the northern part of the Liard Basin and adjacent areas of northern Canada between latitudes 59° 30' N and 60° 30' N and longitudes 121° 30' W and 125° W, to determine the hydrocarbon source potential, thermal maturity and thermal history. The focus of the study is on the optical characteristics and genesis of bitumens and their viability as indicators of thermal maturity. Total organic carbon (TOC) contents indicate that potential oil and gas source rocks occur in the Muskwa, Kotcho, Besa River, Exshaw, Lower Banff, Yohin, Clausen, Golata and Mattson formations; the latter includes thin algal laminites and sapropelic coals. Hydrogen versus oxygen indices indicate that the organic matter comprises Type II kerogen, except for the Golata and Mattson formations which contain mixed Type II and Type III kerogen. Petrographic analysis indicates that the organic components consist of primary and secondary liptinites of marine origin and indigenous microscopic bitumens. In addition, shales in the Golata and Mattson contain structured liptinite macerals, predominantly sporinite derived from Carboniferous mega- and microspores. ... Organic petrology and RockEval-TOC pyrolysis studies were carried out on over 600 samples of shales, siltstones, marls and coals from forty three sections in the Upper Devonian and Carboniferous strata of the northern part of the Liard Basin and adjacent areas of northern Canada between latitudes 59° 30' N and 60° 30' N and longitudes 121° 30' W and 125° W, to determine the hydrocarbon source potential, thermal maturity and thermal history. The focus of the study is on the optical characteristics and genesis of bitumens and their viability as indicators of thermal maturity. Total organic carbon (TOC) contents indicate that potential oil and gas source rocks occur in the Muskwa, Kotcho, Besa River, Exshaw, Lower Banff, Yohin, Clausen, Golata and Mattson formations; the latter includes thin algal laminites and sapropelic coals. Hydrogen versus oxygen indices indicate that the organic matter comprises Type II kerogen, except for the Golata and Mattson formations which contain mixed Type II and Type III kerogen. Petrographic analysis indicates that the organic components consist of primary and secondary liptinites of marine origin and indigenous microscopic bitumens. In addition, shales in the Golata and Mattson contain structured liptinite macerals, predominantly sporinite derived from Carboniferous mega- and microspores.

Thesis (M.S.)--University of Nevada, Reno, 2008. / "August, 2008." Includes bibliographical references (leaves 109-116). Online version available on the World Wide Web.

Thesis (M.S.)--Ohio University, June, 2008. / Title from PDF t.p. Includes bibliographical references.