Geothermal Heat Pump and Heat Engine Systems E-Book

Andrew D. Chiasson

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Serie: Wiley-ASME Press Series
• Sprache: Englisch

Seitenzahl: 766

Veröffentlichungsjahr: 2016

Beschreibung

A unique approach to the study of geothermal energy systems

This book takes a unique, holistic approach to the interdisciplinary study of geothermal energy systems, combining low, medium, and high temperature applications into a logical order. The emphasis is on the concept that all geothermal projects contain common elements of a "thermal energy reservoir" that must be properly designed and managed.

The book is organized into four sections that examine geothermal systems: energy utilization from resource and site characterization; energy harnessing; energy conversion (heat pumps, direct uses, and heat engines); and energy distribution and uses.

Examples are provided to highlight fundamental concepts, in addition to more complex system design and simulation.

Key features:

• Companion website containing software tools for application of fundamental principles and solutions to real-world problems.
• Balance of theory, fundamental principles, and practical application.
• Interdisciplinary treatment of the subject matter.

Geothermal Heat Pump & Heat Engine Systems: Theory and Practice is a unique textbook for Energy Engineering and Mechanical Engineering students as well as practicing engineers who are involved with low-enthalpy geothermal energy systems.

Leseprobe

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Nonlinear Regression Modeling for Engineering Applications

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Stress in ASME Pressure Vessels

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Combined Cooling, Heating, and Power Systems

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GEOTHERMAL HEAT PUMP AND HEAT ENGINE SYSTEMS

THEORY AND PRACTICE

Andrew D. Chiasson, Ph.D., P.E., P.Eng.

Department of Mechanical and Aerospace Engineering,University of Dayton, USA

This Work is a co-publication between ASME Press and John Wiley & Sons, Ltd.

This edition first published 2016© 2016 John Wiley & Sons, Ltd

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Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. It is sold on the understanding that the publisher is not engaged in rendering professional services and neither the publisher nor the author shall be liable for damages arising herefrom. If professional advice or other expert assistance is required, the services of a competent professional should be sought.

Library of Congress Cataloging‐in‐Publication Data

Names: Chiasson, Andrew D, 1966– author.Title: Geothermal heat pump and heat engine systems : theory and practice / Andrew D Chiasson, Ph.D., P.E., P.Eng., Department of Mechanical and Aerospace Engineering, University of Dayton, USA.Description: Hoboken, N.J. : John Wiley & Sons Ltd, 2016. | Includes bibliographical references and index.Identifiers: LCCN 2016015385 (print) | LCCN 2016022646 (ebook) | ISBN 9781118961940 (cloth) | ISBN 9781118961971 (pdf) | ISBN 9781118961964 (epub)Subjects: LCSH: Ground source heat pump systems. | Heat pumps--Thermodynamics. | Heat-engines--Thermodynamics.Classification: LCC TH7417.5 .C44 2016 (print) | LCC TH7417.5 (ebook) | DDC 697–dc23LC record available at https://lccn.loc.gov/2016015385

A catalogue record for this book is available from the British Library.

In Memory of Kirstin Beach Chiasson

Series Preface

The Wiley‐ASME Press Series in Mechanical Engineering brings together two established leaders in mechanical engineering publishing to deliver high‐quality, peer‐reviewed books covering topics of current interest to engineers and researchers worldwide.

The series publishes across the breadth of mechanical engineering, comprising research, design and development, and manufacturing. It includes monographs, references and course texts.

Prospective topics include emerging and advanced technologies in Engineering Design; Computer‐Aided Design; Energy Conversion & Resources; Heat Transfer; Manufacturing & Processing; Systems & Devices; Renewable Energy; Robotics; and Biotechnology.

Preface

Intent and Motivation for this Book

This book is intended as a university‐level textbook for the study of Geothermal Energy Systems. The book is aimed at upper division and graduate students of the emerging field of Energy Engineering, as well as the traditional field of Mechanical Engineering. The book will also be useful to practicing engineers in these fields who are involved with low‐temperature geothermal energy applications.

The emerging (or already emerged) field of Energy Engineering is highly interdisciplinary, mainly grounded in fundamentals of the thermofluid sciences, environmental science, natural sciences, and social sciences, and this book is based on this interdisciplinary viewpoint, while keeping in mind the engineering and practical constraints of the real world. Thus, readers of this book are expected to have introductory background in the natural sciences and thermofluid sciences (i.e., thermodynamics, heat transfer, and fluid mechanics).

This book is the culmination of Geothermal Energy courses I developed and delivered, beginning back in 2009 at the University of Dayton. Then, the first university‐level course I developed had a focus on geothermal heat pumps, but students invariably wondered and asked about hot springs, geysers, and geothermal power plants. Conversely, courses I taught on the subjects of geothermal power plants and direct‐use heating inevitably had students asking, ‘what about those heat pumps I keep hearing about?’. Therefore, I felt the motivation to develop materials to unify all geothermal uses under one cover, allowing students to read about geothermal topics they were curious about, even though not necessarily the focus of their current study. Thus, this book is divided into four parts after Chapter 1, which describes general considerations of developing a geothermal energy project. The four parts are: (i) geothermal energy utilization and resource characterization, (ii) harnessing the resource, (iii) energy conversion, and (iv) energy distribution. These elements are common to all types of geothermal energy project (as well as other uses of renewable energy sources), regardless of temperature and use.

So why write a textbook? I believe that a course in Geothermal Energy in an Energy Engineering curriculum or other applied science program is very important. The field of Energy Engineering has emerged as a distinct field of engineering practice in its own right, and is a highly interdisciplinary field, with sources, applications, and uses of energy crossing all traditional fields of engineering. World population growth continues. Developing countries are urbanizing at increasing rates. How will these energy needs be met sustainably? One potential way is by meeting targets toward net‐zero buildings, where buildings themselves (or groups of buildings) become providers as well as consumers of energy, both thermal and electrical. We spend much of our lives in buildings, but also take them for granted. Buildings of the future must not only meet energy challenges but also be environmentally sustainable and of high comfort for occupants. Optimal ways of reducing, supplying, and using this energy will be the key role of the next generation of Energy Engineers. Geothermal Energy has the potential to meet such needs.

The study of Geothermal Energy, in general, is somewhat of a balance of theory and practice. In other words, one can get wrapped up in the theoretical study of complex heat transfer problems, but in reality, engineers are faced with real‐world uncertainties of the subsurface geology, dynamic behavior of weather, dynamic behavior of buildings, and economic and environmental constraints. Some solution methods to subsurface geothermal heat transfer problems are difficult to impossible to solve without computer aid, and developing workable solutions can take up the better part of a semester course. Thus, this book aims to present equations and theoretical approaches in a fundamentally easily understandable way, and then provides software tools on a companion website, readily adaptable for use.

Finally, this book is not just about ‘geothermal energy’. Even if readers aren’t particularly interested in the topic, it is hoped that this book will allow readers to gain insight about ‘applied’ knowledge in environmental heat transfer, applied thermodynamics, creative power generation, and energy‐efficient building (or ‘green building’) design.

Engineering Education in the Twenty‐first Century

The twenty‐first century has marked a transition in engineering education. Yesterday’s engineers spent the majority of their time substituting values into formulas and obtaining numerical results. Just a few decades ago, engineers used slide rules, and then graduated to electronic calculators; more complicated solutions relied on tabulated data or nomographs. Today, formulaic calculation and ‘number crunching’ are left to computers, thus allowing more complex problems to be solved at faster and faster rates. Computer‐based solutions now enable engineers to examine numerous ‘what‐if?’ scenarios, and readily find optimal solutions to problems, based on cost or some other metric.

Thus, the engineering curriculum has seen increasing use of computer application with engineering equation solvers and other numerical software packages. More than ever, I believe that current and future engineers need a firm grasp of basic principles so that complex problems can be formulated and optimized, and results correctly and accurately interpreted. Further, engineers need a grasp of real‐world constraints such as cost, legalities, and environmental impact. This is the emphasis of this book.

Supplemental Materials

A companion website is a key component of this book, which contains software tools to allow users of this book to apply fundamental principles and solve real‐world problems. The companion website includes:

An Excel‐based suite of design tools for sizing ground heat exchangers and performing pressure‐drop calculations in pipes.

Electronic files in

Engineering Equation Solver

(

EES

) for simulating the thermodynamic performance of heat pump and heat engine cycles.

Meeting Different Course Needs

Instructors who adopt this book can choose to: (1) give a light treatment of theory and focus on the practical use of the provided design software tools and economics, or (2) give a more in‐depth treatment of the theory with companion practical application of the provided design tools, or (3) give a near entire treatment of theory, leaving solutions and applications for the students to develop and/or improve. In my experience, option (1) is most suitable for a college‐level course at the senior, undergraduate level, or for course schedules not covering a full semester. Option (2) is suitable for a senior or graduate‐level course on a semester schedule, and option (3) is suitable for more advanced graduate students completing courses in ‘special topics’ or completing research projects or theses.

Andrew D. ChiassonFebruary 2016

About the Companion Website

Don’t forget to visit the companion website for this book:

www.wiley.com/go/chiasson/geoHPSTP

There you will find valuable material designed to enhance your learning, including:

Data Files for Exercise Problems

Example Files in EES

Design Tool Suite (for sizing GHXs and calculating pipe pressure drop)

Scan this QR code to visit the companion website

1Geothermal Energy Project Considerations

1.1 Overview

The main focus of this book is geothermal heat pump applications for buildings. However, this first chapter first introduces readers to general considerations for renewable/clean energy project analysis. Then, specifics of geothermal energy projects are discussed through broad considerations of geothermal energy utilization, of which geothermal heat pumps is just one type. Elements of geothermal energy systems are discussed, laying the foundation for the organization of material in this book.

The chapter describes geothermal energy from the perspective of resource temperature in the context of high‐, medium‐, and low‐temperature applications, emphasizing that the end use of the energy, at least in theory, can be any application where thermal energy is involved.

Learning objectives and goals:

Be aware of favorable conditions for alternative energy projects.

Understand general decision analysis of renewable/clean energy systems.

Draw analogies between geothermal and other renewable energy system analysis.

Appreciate the role of resource temperature in defining a geothermal energy project.

Appreciate the inherent risks in undertaking a renewable/clean energy project.

Realize the similarities in project development in all geothermal energy projects.

1.2 Renewable/Clean Energy System Analysis

Energy project stakeholders, investors, and decision‐makers are mainly interested in project viability and feasibility. RetScreen® International (2004) provides a good discussion for general decision‐making. For conventional and especially for renewable/clean energy projects under consideration, Figure 1.1 shows general steps taken for advancing such projects to completion. At each step, a ‘go/no‐go’ decision can be made by stakeholders as to whether or not to proceed to the next step of the development process. Thorough and accurate pre‐feasibility and detailed feasibility studies are critical to helping the project owner reject projects or scenarios that do not make sense, either from a financial, regulatory, logistical, or other perspective. Accurate pre‐feasibility and detailed feasibility analyses also facilitate development and engineering efforts prior to construction. The tools and techniques presented in this book are, in part, aimed toward that end.

Figure 1.1 General flow of conventional and alternative energy projects

The discussion that follows describes the boxes shown in Figure 1.1.

Favorable Project Conditions. In general, many decision‐makers are not familiar with implementation of renewable/clean energy technologies and when they should be considered. The author has seen many misconceptions regarding the use of geothermal energy. One common misconception is, ‘If you have a high temperature geothermal resource, you essentially have a gold mine’. The reality is: Does the capital exist to develop the resource? What is the revenue stream for the energy? Is there a business plan or a market for the energy? Who will operate and maintain any equipment? Another common misconception is, ‘Geothermal heat pumps can be applied everywhere’, but the reality is: How easy is your building to retrofit to a heat pump system? What’s really underground at your site? How sustainable will the reservoir be? Are there qualified contractors in your area?

Renewable/clean energy systems are typically capital intensive, with low operating costs that are usually weighed against the operating cost of a conventional energy system. The following is a general set of conditions as to when a renewable/clean energy project might be considered:

Need for an energy system.

An opportune time for considering a renewable/clean energy system is when an energy system is being planned or replaced. The capital cost of the renewable/clean energy system can be offset by the avoided cost of the conventional system. In retrofit cases, for example in buildings, retrofitting the building to be compatible with a renewable/clean energy system may be prohibitive.

High Conventional Energy Costs.

Obviously, when conventional energy costs are high, the relatively low energy cost of a renewable/clean energy system is attractive. Thus, interest in renewable/clean energy systems is typically proportional to conventional energy costs.

Available Funding and Financing.

The relatively higher capital cost of renewable/clean energy projects is often a substantial barrier. Some jurisdictions promote clean energy projects with financial incentives, such as grants and tax rebates. Some companies offer third‐party ownership of renewable/clean energy projects, where they bear the cost of the project and sell lower‐cost energy to the project proponent.

Qualified Contractors, Installers, and Maintenance Personnel.

Renewable/clean energy systems (particularly geothermal heat pump systems) typically involve specialized, non‐traditional training and certification. If qualified personnel are not local, installation costs can become prohibitive. At early stages of a project, complexity of the system should also be considered; local availability of qualified personnel for system maintenance may eliminate a project from consideration.

Persistent Project Stakeholders.

Seeing a renewable/clean energy project through to completion, especially a complex one, can be a daunting task. Diligent project management is required, involving coordination of numerous trades, monitoring budgets, navigation through complicated regulations, and, perhaps most of all, persistence.

Simple Legal and Permitting Processes.

Development costs and schedule delays are minimized when laws and regulations are understood by the project team, and when these laws and regulations do not unfairly disadvantage a renewable/clean energy project.

Adequate, Sustainable Resource.

An adequate resource is necessary for any renewable/clean energy project. However, special considerations are needed for geothermal resources, which are discussed in

Chapter 3

. In particular, a geothermal venture involves risk because the resource cannot be completely observed with depth. Further, the resource is finite, and proper resource management is necessary.

Pre‐Feasibility Study. The pre‐feasibility analysis determines whether the proposed project has a good chance of satisfying the owner’s requirements for profitability and/or cost‐effectiveness. It is characterized as a ‘desktop’ study, involving the use of readily available site and resource data, ±30–50% cost estimates, and simple calculations and professional judgement often involving experience with other projects. For geothermal projects, a site visit is very important to observe surface features, access, and potential site barriers. A conceptual model of the resource is generally produced.

Detailed Feasibility Study. As the name implies, this is more in‐depth analysis of the project’s viability. A detailed feasibility study must provide information about the physical characteristics, financial viability, and environmental, social, or other impacts of the project, such that the owner can come to a decision about whether or not to proceed. It is characterized by the collection of refined site, resource, cost, and equipment data. For geothermal projects, the resource is fully defined, which typically involves drilling and measuring of thermal exchange properties. A conceptual model of the resource is refined and completed. In some cases, detailed computer simulation is undertaken. Project costs are refined through solicitation of price information from equipment suppliers.

Engineering and Development. If, based on the feasibility study, the project owner decides to proceed with the project, then engineering and development are the next step. Engineering includes the planning and technical design of the physical aspects of the project. Development involves the planning, arrangement, and negotiation of financial, regulatory, contractual, and other non‐physical or ‘soft’ aspects of the project. Some development activities, such as training, customer relations, and community consultations, extend through the subsequent project stages of construction and operation. Even following significant investments in engineering and development, the project may be postponed or abandoned prior to construction because financing cannot be arranged, environmental approvals cannot be obtained, the pre‐feasibility and feasibility studies overlooked important cost items, qualified contractors are not available, or for other reasons.

Procurement, Construction, and Commissioning. Finally, the project is built and put into operation. Prior to turning the project over to the owner, a proper commissioning process is key. The commissioning process involves a set of procedures to verify that all components of the system are operational, and that the system functions as it was intended and designed.

1.3 Elements of Renewable/Clean Energy Systems

The study of renewable energy systems can, in general, be subdivided into the following five elements: (i) energy loads and resource characteristics, (ii) harnessing the energy, (iii) energy conversion (to useful energy), (iv) optional energy storage, and (v) energy distribution.

Figure 1.2 shows these elements specific to geothermal energy systems. It should be emphasized that these elements are not mutually exclusive, but rather they are useful for understanding energy system components. Regarding geothermal projects, these elements can, however, and often do, represent the various specialty areas. For example, consulting scientists and engineers may be involved in resource characterization and/or resource harnessing, but not in the conversion or energy distribution stages.

Figure 1.2 Elements of geothermal energy systems

Thus, the study of geothermal energy systems as presented in this book follows the aforementioned four elements of the system. Following this introductory chapter, Part I addresses energy loads and the geothermal resource. Part II covers the numerous Earth‐coupling types used to harness stored thermal energy for geothermal heat pump applications. Part III discusses the various methods for converting geothermal energy to useful energy. Finally, Part IV discusses methods for distributing the energy. The focus of each part is on geothermal heat pumps, but higher‐temperature geothermal applications are intermixed to give readers a broader perspective of the similarities of geothermal projects.

1.4 Geothermal Energy Utilization and Resource Temperature

We will see in Chapter 3 that there are a number of factors that dictate the end use of a geothermal resource, but the end use ultimately depends on the resource temperature. Thus, there have been a number of classification methods aimed at categorizing geothermal resources by temperature. Here, we will use the following gross temperature categories:

high‐temperature uses:                                   

T

resource

 > 150 °C

medium‐temperature uses:                            90 °C < 

T

resource

 < 150 °C

low‐temperature uses:                                     30 °C < 

T

resource

 < 90 °C

ambient temperatures (heat pump uses):    ∼0 °C < 

T

resource

Note that there is no distinct break between categories. The geothermal power industry typically uses only the top three temperature categories (a, b, and c), based on cut‐off temperatures of economical electric power generation, which has historically not been economical for resources with temperatures below about 150 °C. However, binary organic Rankine cycle power plants, under favorable circumstances, have demonstrated that it is possible to generate electricity economically above 90 °C. A fourth category (d) is added here to distinguish the geothermal heat pump applications.

Figure 1.3 shows some of the many past and/or current uses of geothermal energy worldwide. As shown in this figure, there are many other ‘high‐temperature’ resource use possibilities aside from electric power generation. Many of the medium‐temperature uses are termed ‘direct uses’ because there is no energy conversion process, and the resource temperature matches or exceeds that required by the load. However, as noted in Figure 1.3, ambient groundwater can also be used for direct cooling applications.

Figure 1.3 Worldwide past and present utilization of geothermal energy based on resource temperature

Figure 1.4 Schematic of a flash steam geothermal power plant

1.5 Geothermal Energy Project History and Development

In the geothermal industry, projects are typically identified by their end use and associated resource temperature. Thus, power plant projects are associated with high‐temperature reservoirs, direct‐use projects are associated with low‐ to medium‐temperature reservoirs, and geothermal heat pump projects are associated with ambient‐temperature reservoirs. Note that, strictly speaking, such a classification scheme is ambiguous because the term ‘direct use’ means that the resource is used directly owing to its temperature match to the load, and thus a direct‐use application can occur over a large temperature range. Further, thermally driven heat pump applications are utilized with moderate‐temperature resources. Nevertheless, in the subsections that follow, we will use these descriptors to illustrate typical development of geothermal projects.

1.5.1 Geothermal Power Plants

1.5.1.1 Overview

The first geothermal power was generated at Larderello, Italy, in 1904. According to Lund (2007), the first commercial power plant (250 kW) was commissioned in 1913 at Larderello, Italy. Owing to the impurity of the geothermal fluids, steam was generated in a secondary loop isolated from the geothermal fluids by a heat exchanger. In the United States, an experimental 35 kW plant was installed at The Geyers geothermal field, California, in 1932, and provided power to the local resort. These developments were followed in New Zealand at Wairakei in 1958, an experimental plant at Pathe, Mexico, in 1959, and the first commercial plant at The Geysers in the United States in 1960. Japan followed with 23 MW at Matsukawa in 1966. All of these early plants used steam directly from the Earth (dry steam fields), except for New Zealand, which was the first to use flashed or separated steam.

According to Lund (2007), Iceland first produced power at Namafjall in northern Iceland, from a 3 MW non‐condensing turbine. This was followed by plants in El Salvador, China, Indonesia, Kenya, Turkey, Philippines, Portugal (Azores), Greece, and Nicaragua in the 1970s and 1980s. Later plants were installed in Thailand, Argentina, Taiwan, Australia, Costa Rica, Austria, Guatemala, and Ethiopia, with the latest installations in Germany and Papua New Guinea.