Second edition of the book Energy Systems: A New Approach to Engineering Thermodynamics
A new education paradigm
We have developed over the past thirty-five years a new way of teaching thermodynamics applied to energy conversion now used in more than one hundred and twenty higher education institutions, at both undergraduate and graduate levels (engineering schools, universities) as well as in vocational training.
The change in the education paradigm we have introduced is based on a shift of knowledge acquired by students. The writing of equations describing changes undergone by fluids is drastically reduced, the calculations being performed by a simulator such as Thermoptim without learners needing to know the details. They devote most of the time on the one hand learning technologies, and secondly reflecting on the architecture of both conventional and innovative thermodynamic cycles, graphically building and setting models of various energy systems instead of theoretical cycles caricaturally simplified in order to be analytically calculable.
The new teaching method has the distinction of being at the same time much simpler than conventional approaches for the introduction to the discipline, and much more powerful for confirmed students who can go further in their studies thanks to a strong and open modeling environment. They can work on real-world complex innovative cycles currently being studied in laboratories and companies.
We published in 2011 a book entitled “Energy Systems, a new approach to engineering thermodynamics”, which had a double objective: on the one hand to allow beginners to understand the design principles of energy systems and to have an overall vision of the different technologies usable for their realization, and on the other hand to provide its confirmed readers with advanced methods of analysis of these systems. It showed how a structured approach to studying energy technologies can be implemented using the Thermoptim software package.
This first book is approximately 1,100 pages and, despite the simplifications made by the proposed approach, it can be a bit difficult for a number of readers.
This book, while following the same global logic as the 2011 book, does not go as much in the details. In order to simplify the content, sections that were intended for advanced readers have been removed and theoretical developments have been limited to the essential.
As indicated by its title, this book deals with energy systems, i.e. energy conversion technologies (ECTs) considered as systems based on sets of elementary components coupled together. Although it mainly addresses thermodynamic energy conversion, it covers a very large field, including a variety of cycles:
conventional as well as innovative steam power plants
new and renewable energy conversion
Generation I to IV nuclear energy conversion
Structure of the book
The book comprises four main Parts:
1) After a first chapter which presents the new pedagogical paradigm that we have developed over the past thirty years, it begins by introducing in a first Part (84 pages) the essential concepts which must be understood for studying the cycles of three basic energy technologies: the steam power plant, the gas turbine and the refrigeration machine. The chosen approach follows a presentation called CFRP for Components, Functions and Reference Processes.
In the CFRP presentation, we start by describing the architectures of these various technologies and the technological solutions implemented. We then show that despite their diversity, the components only perform four main functions, themselves corresponding to three reference changes undergone by the fluids which pass through them.
This analysis, initially functional, leads to the essential notion of reference processes, models of fluid behavior in machines, and quite naturally leads to the study of the properties of these fluids.
The approach is as light as possible in order to allow students to learn to model, gradually and by example, heat conversion technologies. We show in particular that one can present the essential of the concepts without using a state function which can be difficult to understand well, entropy.
After having introduced some essential notions of thermodynamics, energy exchanges of a system with its environment are analyzed and the first law is presented.
The representation of the cycles in the (h, ln (P)) chart makes it possible to visualize the physical phenomena at play and the few reference processes undergone by the working fluids.
The way in which these cycles can be modeled with the Thermoptim software package is the subject of guided explorations of pre-built models.
2) We are advocating for the lightest possible and progressive approach, in a spiral, where new concepts are only introduced at the precise moment when they are needed, even if it means going back to them later to give further details. It is light to limit the cognitive load of the learners, and progressive to maintain their motivation. Such an approach can be considered as minimalist.
This is why, once we have shown in the first Part that learners can very simply model the basic thermodynamic cycles, it becomes possible in a second Part (105 pages) to provide theoretical, technological and methodological supplements that will be used in more complex cycle studies of Parts 3 and 4.
To be perfectly consistent with what has just been said, it would be necessary to alternate the theoretical and methodological sections and the sections of application to technologies, which would risk giving the book a bushy appearance.
For the sake of clarity, we have therefore gathered in this second Part most of the supplements presented.
Specific supplements will however be provided at the time they are used (e.g. moist gases).
Theoretical supplements presented in Part 2 relate to combustion, heat exchangers, and entropy. Methodological supplements deal with process integration (pinch method), exergy balances and productive structures. Technological supplements are related to steam systems components: boilers, steam generators, steam turbines and cooling towers.
3) In the third Part, (185 pages) we start from the cycles introduced initially, and we show how their efficiency can be improved, which allows learners to study main conventional power and refrigeration cycles.
The guiding principle behind these analyzes is the reduction of irreversibilities, special attention being paid to those that arise from temperature differences with external sources and during internal regenerations. In addition, the value of staged compression and expansion is highlighted whenever possible.
In this context, exergy analyzes are of great interest, because they make it possible to quantify irreversibilities. This is why we present numerous exergy balances of the cycles studied, the emphasis being on the interpretation of their results rather than on the underlying theory. As we explain in Chapter 6, obtaining them is greatly facilitated by the use of productive structures, so that the use of exergy balances is done without any difficulty, at least for Part 3.
Classical ECTs are reviewed, analyzed as systems implementing the components whose operation has been studied previously. The link is made between scientific knowledge and technological achievements, which are presented in more detail than in the previous chapters.
Chapters 12 and 13 deal with air conditioning and absorption cycles, now classic, which justifies their inclusion in Part three.
4) The fourth Part (145 pages) is devoted to the study of innovative cycles with low environmental impact: advanced gas turbine cycles, Stirling engines, future nuclear reactors, oxycombustion cycles, new and renewable energy thermodynamic cycles, evaporation, mechanical and thermal vapor compression, desalination, drying by hot gas, electrochemical converters.
Some examples of exergy balances are also provided. For certain cycles, such as those relating to evaporation or drying, their interpretation is a little more difficult than for those studied previously.
In this book, the learning of modeling is carried out on the one hand in a very progressive manner, the more complex concepts being introduced contextually, as and when required, and on the other hand by realistic examples, the reader being invited to carry out guided explorations of 45 models of about 30 different energy systems.
We speak of a light pedagogical presentation because we seek to limit as much as possible the baggage in mathematics and physics necessary for the understanding of these technologies, our objective being to make them accessible to readers unfamiliar with the language of specialists in thermodynamics.
During the first two thirds of the book, that is to say up to Chapter 11 inclusive, we have thus limited the use of theoretical developments and equations to the strict minimum. From these chapters to the end of the book, we have reintroduced them, considering that at this stage of advancement in the book, even readers most reluctant initially by the mathematical and physical aspects would find the motivation to delve into them if the topic really interests them. Many examples are provided, with the equations retained in the models, a number of which use the external classes of Thermoptim, where these equations are encapsulated. Java code for these classes is available.
In around 550 pages, readers are presented essential concepts which allow them to understand both the functioning of energy systems ensuring thermodynamic heat conversion and the way in which they can be modeled.
This book thus constitutes a much easier complement to the first edition of the book Energy Systems, which deals with the subject in a more in-depth and more exhaustive manner.
Three types of inserts are included in the book. They highlight key issues, among which self-assessment exercises, worked examples and guided explorations, and provide links to the associated numerical resources.
The whole book is illustrated by numerous real-life examples (about 125) of cycles modeled with Thermoptim, which provide the reader with models whose structure or settings he may customize as he wishes to perform various simulations. The files of these examples are available for teachers, but not for their students.
The list of these examples, of varying difficulty, is given in this Thermoptim-UNIT portal with some comments and suggestions on ways in which they can be used educationally, depending on the context and the objectives pursued by teachers.
More generally, many digital resources for teaching energy systems have been gradually collected into this portal whose content is freely accessible, with few exceptions, including solutions of some exercises and problems, among which are those presented in this book.
Readers will find about 45 self-assessment online activities, the main purpose of which is to allow them to check their understanding of the different concepts presented. Marks are not recorded or transmitted to anyone. They simply give an indication of the quality of the answers.
These self-assessment activities are of four types:
Drag and drop onto image (ddi) exercises allow learners to check if they can find their way around a sketch or a chart. They operate by simple drag and drop;
Gap-fill exercises (gfe) with a contextual image require a little more concentration on the reader's part, but is very fruitful in ensuring that difficult concepts are well understood. From a pedagogical point of view, it is an excellent exercise because they are asked to rephrase what has been presented in the book in order to construct sentences that make sense, the missing texts being offered in drop-down menus;
Categorization exercises (cat) complement the previous two activities well: readers organize elements into categories and thus learn to distinguish their characteristics;
Finally, single-choice questions and multiple-choice questions (quiz) allow them to test their knowledge in a fairly broad way, but they are not very user-friendly tools.
Objectives of this book
The goals we set ourselves have led us to identify three major transverse themes that are found throughout the presentations:
theoretical foundations (whose presentation has been simplified as much as possible);
an original modeling approach;
a detailed presentation of technologies, often absent from books on these subjects offered to learners
For beginners, the major interest of Thermoptim is that it can help them to model complex energy systems simply, without having to write an equation or program. It discharges its users of many problems, including computational ones, and enables them to make analyses that they could not pursue otherwise, especially when starting out. It becomes possible, when learning the discipline, to focus on a qualitative approach, the calculations required for quantitative studies being performed by the software. Note that the name of this tool has a double meaning: it does allow one to optimize thermodynamic systems, but above all it allows one to learn this discipline with optimism...
Under these conditions, energy systems operation can be studied using a completely new pedagogy, where only a small number of elements must be considered: firstly those used to describe the systems studied, and secondly those used to set the simulator components.
If done this way, it is not necessary, at least initially, to take into account the details of the equations allowing calculation of the process involved: Thermoptim automatically does this. Learning the discipline is limited to these basic concepts and their implementation in the package. The memorization effort and cognitive load required for beginners are greatly reduced, allowing them to focus their attention on understanding the basic phenomenological concepts and their practical implementation.
Thus, Thermoptim permits, without writing a single line of code, to calculate energy systems from simple to complex.
In summary, we pursue three objectives:
allow learners firstly to understand the functioning of various components at stake in energy systems and how they are assembled, emphasizing the technological aspects;
show how it is possible through the use of Thermoptim to model and calculate them very simply but with great precision, and make the reader familiar with this working environment;
provide the reader with methodological guidance, simple or advanced, for analyzing the systems he/she studies. In this spirit, a significant place is devoted to exergy methods that are increasingly regarded as among the best suited to perform optimization studies, as they can take into account both the amount of energy put into play and its quality.
A working tool on many levels
This book can be read and used as a working tool on several levels:
for an introduction to the discipline with an illustration of its implementation in Thermoptim: you can then simply understand the different technologies, the undrelying physical phenomena and the methodologies recommended, possibly using the package somewhat blindly;
for a deepening of the field, it presents not only the calculation principles and the basic equations, but also explains how to build exergy balances, implement the pinch method etc.;
for software users, this book is a scientific complement to the documentation provided with the tool, allowing those interested to better understand how the calculations are made and even to personalize it. Note, however, that the first edition is much more detailed in this respect than this one.
It follows that the book is deliberately composed of a series of sections that are on different planes, some more theoretical, others more applied and technological, and others methodological, concerning in particular the use of Thermoptim.
In this way, readers wishing to do an overview of the book will be guided through the research of basic concepts needed, especially to use the software properly, while those who wish to invest further in the discipline will benefit from a consistent and progressive presentation.
Pedagogically, this book and Thermoptim can be used in various contexts, under both a traditional approach (neo-behaviorist or objectivist) and a more recent constructivist approach. We hope it will help colleagues to overcome difficulties that they may face in their practice.
For supporters of a conventional approach, Thermoptim allows them particularly to enrich the classical presentation by accurate simulations and to make students study multiple and realistic examples. In a constructivist approach, the book and the software are in addition tools allowing students to work independently to explore a wide field and analyze very open topics:
for beginners, it is a structured environment that reduces the cognitive load while acquiring the vocabulary and basic concepts encapsulated in the screens. Once this vocabulary is learned, cooperative learning with peers and teachers is strengthened;
very quickly, it becomes possible to work on realistic problems and not caricatures (as conventionally internal combustion engines with perfect air as working fluid). In addition, during internships, students using Thermoptim are fully operational in the company where they work, which is very exciting for them and leads them to engage more thoroughly;
for experienced users, Thermoptim allows them to study very complex systems (for example, Areva Framatome used Thermoptim to optimize combined cycles and cogeneration cycles coupled with high temperature nuclear reactors,).
The reader will understand that we seek above all to make as accessible as possible the study of energy systems, demonstrating very concretely how realistic models can be developed to represent them. This bias has led us to voluntarily limit our discussion of scientific issues to key points, especially regarding the fundamentals of thermodynamics and heat transfer. As a result, the book loses in generality what it gains in ease of use: know-how is privileged compared to knowledge itself. Readers interested in further developments may if they wish refer to documents given in the bibliography.
Experienced engineers will find a coherent body of theory and practice through which they can become quickly operational, without having to get personally involved in solving equations or in the development of a computer modeling environment.