Supercritical CO2 geothermal energy system analysis

There has been considerable interest in the possibility of using supercritical carbon dioxide (SCCO2) as a geothermal heat mining fluid instead of water. Some favourable fluid transport properties may prove to give an advantage in some circumstances. The low viscosity to density ratio suggests higher mass flow rates and better suitability to low permeability to low permeability reservoirs may be possible. Higher frictional losses in the wellbores may degrade that advantage. It has been shown that SCCO2 has the potential to utilise buoyancy effects such that a thermosiphon circulates the geothermal fluid without the need for a pump. In addition, it has been proposed that SCCO2 could be used to drive a turbine directly rather than a conventional binary heat exchange system. This could dramatically reduce surface plant complexity and cost. This study details the creation of a Matlab model of the subsurface circuit of geothermal fluid. After establishing a reference case to study general fluid and system behaviour, the model is used to test and compare the effects of wellbore diameter variation, reservoir depth, permeability and temperature on the net exergy and thermal efficiency using each of water and SCCO2. For the specific test cases, SCCO2 was shown to perform significantly better than water with increased well bore diameter, low permeability and low temperature reservoirs. The performance was found to degrade with shallower reservoirs; although this leads to observations that the SCCO2 system operates on a narrow band of efficiency which could make the system less robust than comparable water based system

Land Use Change from Non-urban to Urban Areas

This reprint is related to land-use change and non-urban and urban relationships at all spatiotemporal scales and also focuses on land-use planning and regulatory strategies for a sustainable future. Spatiotemporal dynamics, socioeconomic implication, water supply problems and deforestation land degradation (e.g., increase of imperviousness surfaces) produced by urban expansion and their resource requirements are of particular interest. The Guest Editors expect that this reprint will contribute to sustainable development in non-urban and urban areas

USING SOCIALLY SENSED BIG DATA TO MODEL PATTERNS AND GEOGRAPHIC CONTEXT OF HUMAN ACTIVITIES IN CITIES

Understanding dynamic interactions between human activities and land-use structure in a city is a key lens to explore the city as a complex system. This dissertation contributes to understanding the complexity of urban dynamics by gaining knowledge of the interactions between human activities and city land-use structures by utilizing free-accessible socially sensed data sources, and building upon recent research trend and technologies in geographical information science, urban study, and computer science. This dissertation addresses three main questions related to human dynamics: 1) how human activities in an urban environment are shaped by socioeconomic status and the intra-city land-use structure, and how in turn, the knowledge of socioeconomic status-activity relationships can contribute to understanding the social landscape of a city; 2) how different types of activities are located in space and time in three U.S. cities and how the spatiotemporal activity patterns in these cities characterize the activity profile of different neighborhoods in the cities; and 3) how recent socially sensed information on human activities can be integrated with widely-used remotely sensed geographical data to create a novel approach for discovering patterns of land use in cities that are otherwise lacking in up to date land use information. This dissertation models the associations between socioeconomics and mobility in the Washington, D.C. metropolitan area as a case study and applies the learned associations for inferring geographical patterns of socioeconomic status (SES) solely using the socially sensed data. This dissertation also implements a semi-automated workflow to retrieve activity details from socially sensed Twitter data in Washington, D.C., the City of Baltimore, and New York City. The dissertation integrates remotely-sensed imagery and socially sensed data to model the dynamics associated with changing land-use types in the Washington, D.C.-Baltimore metropolitan area over time

Proceedings of 2013 Kentucky Water Resources Annual Symposium

This symposium was planned and conducted as a part of the state water resources research institute annual program that is supported by Grant/Cooperative Agreement Number G11AP20081 from the United States Geological Survey. The contents of this proceedings document and the views and conclusions presented at the symposium are solely the responsibility of the individual authors and presenters and do not necessarily represent the official views of the USGS or of the symposium organizers and sponsors. This publication is produced with the understanding that the United States Government is authorized to reproduce and distribute reprints for government purposes

Supercritical carbon dioxide geothermal energy system analysis

There has been considerable interest in the possibility of using supercritical carbon dioxide (SCCO2) as a geothermal heat mining fluid instead of water. Some favourable fluid transport properties may prove to give an advantage in some circumstances. The low viscosity to density ratio suggests higher mass flow rates and better suitability to low permeability reservoirs may be possible. Higher frictional losses in the wellbores may degrade that advantage. It has been shown that SCCO2 has the potential to utilise buoyancy effects such that a thermosiphon circulates the geothermal fluid without the need for a pump. In addition, it has been proposed that SCCO2 could be used to drive a turbine directly rather than a conventional binary heat exchange system. This could dramatically reduce surface plant complexity and cost. This study details the creation of a Matlab model of the subsurface circuit of geothermal fluid. After establishing a reference case to study general fluid and system behaviour, the model is used to test and compare the effects of wellbore diameter variation, reservoir depth, permeability and temperature on the net exergy and thermal efficiency using each of water and SCCO2. For the specific test cases, SCCO2 was shown to perform significantly better than water with increased well bore diameter, low permeability and low temperature reservoirs. The performance was found to degrade with shallower reservoirs; although this leads to observations that the SCCO2 system operates on a narrow band of efficiency which could make the system less robust than comparable water based system

Recent Progress in Urbanisation Dynamics Research

This book is dedicated to urbanization, which is observed every day, as well as the methods and techniques of monitoring and analyzing this phenomenon. In the 21st century, urbanization has gained momentum, and the awareness of the significance and influence of this phenomenon on our lives make us take a closer look at it not only with curiosity, but also great attention. There are numerous reasons for this, among which the economy is of special significance, but it also has many results, namely, economic, social, and environmental. First of all, it is a spatial phenomenon, as all of the aspects can be placed in space. We would therefore like to draw special attention to the results of urbanization seen on the Earth's surface and in the surrounding space. The urbanization–land relation seems obvious, but is also interesting and multi-layered. The development of science and technology provides a lot of new tools for observing urbanization, as well as the analyses and inference of the phenomenon in space. This book is devoted to in-depth analysis of past, present and future urbanization processes all over the world. We present the latest trends of research that use experience in the widely understood geography of the area. This book is focused on multidisciplinary phenomenon, i.e., urbanization, with the use of the satellite and photogrammetric observation technologies and GIS analyses

Nighttime Lights as a Proxy for Economic Performance of Regions

Studying and managing regional economic development in the current globalization era demands prompt, reliable, and comparable estimates for a region’s economic performance. Night-time lights (NTL) emitted from residential areas, entertainment places, industrial facilities, etc., and captured by satellites have become an increasingly recognized proxy for on-ground human activities. Compared to traditional indicators supplied by statistical offices, NTLs may have several advantages. First, NTL data are available all over the world, providing researchers and official bodies with the opportunity to obtain estimates even for regions with extremely poor reporting practices. Second, in contrast to non-standardized traditional reporting procedures, the unified NTL data remove the problem of inter-regional comparability. Finally, NTL data are currently globally available on a daily basis, which makes it possible to obtain these estimates promptly. In this book, we provide the reader with the contributions demonstrating the potential and efficiency of using NTL data as a proxy for the performance of regions

Groundwater: A Community’s Management of the Invaluable Resource Beneath its Feet

Understanding the impact of human decisions on vital resources is a core task of environmental sociology, which studies the interaction between human society and the environment. The overarching theme of this research is the economicenvironmental relationship in U.S. public policy, using a case study of a specific environmental resource problem in a specific region. It fuses basic assumptions of two economic growth models (treadmill of production and the urban growth machine) to examine the extent to which these assumptions permeate the worldviews of policymakers and those who advise them. When the growth imperative is a priority in their worldviews, then the paradigm shapes policy decisions favorable to growth. When the growth imperative paradigm dominates the decision-making structure, then policy decisions favor economic growth over concerns for and at the expense of environmental resources. This is the case because economic growth requires unlimited commoditization and exploitation of finite resources. The results are impairment of both the quantity and quality of natural resources on which communities depend for growth and their existence. This research examines the economic-environmental relationship in a case study of the Memphis, Tennessee area to ascertain how policy decisions that promote growth affect groundwater and may have sparked an inter-state water conflict. The State of Mississippi filed a federal lawsuit against Memphis and its utility Memphis Light, Gas and Water over rights to groundwater, the sole source of drinking water. The study ascertains that the predominance of the growth paradigm is linked to policymakers’ perspectives and reflected in their decisions that impair the quantity and quality of vital environmental resources. The case demonstrates how the growth imperative contributes to resource depletion, which can lead to conflict among users of a common resource

Numerical study of downhole heat exchanger concept in geothermal energy extraction from saturated and fractured reservoirs

Geothermal energy has gained a lot of attention recently due to several favorable aspects such as ubiquitously distributed, renewable, low emission resources while leveraging the advances in the associated technologies such as directional drilling and low enthalpy power generation plant. However, there are still many challenges such as the high initial capital cost of drilling and surface facilities, environmental risk of seismicity due to the induced disequilibrium in the formation, and sustainability of project over designed operational life. Traditional downhole heat exchangers (DHE) could potentially reduce the capital cost and the risk of seismicity, but they are unable to maintain a sustainable geothermal energy production over the operational life due to the rapid cooling down of formation in the vicinity of the wellbore. In this study, a novel DHE design is introduced to enhance the energy production rate as well as sustainability for mainly two types of geothermal reservoirs: saturated geothermal reservoirs and enhanced/engineered geothermal systems (EGS). Modeling of DHE is based on the concept of thermal resistance. A geothermal reservoir simulator is built reusing components of an existing blackoil simulator by adding thermal energy transport equations and fracture representation (discrete fracture network). Several verification and validation tests are carried out. Parametric studies are presented for various configurations of DHE and thermodynamic analysis is carried out for the binary power plant cycle. In addition, the geothermal reservoirs Camerina A and Raton Basin are presented as case studies for saturated geothermal reservoir and EGS, respectively. In saturated geothermal reservoirs, the performance of DHE is improved significantly by exploiting forced convection. For EGS, the overall heat extraction rate is also enhanced by adding DHE