Introduction

In Chapter 1, the concepts of thermodynamics were introduced, and a consistent exposition of thermodynamics' basic laws and associated system properties was offered. Out of an infinite set of properties and a limited number of defined interactions, only a few are relevant in any given study, and these include a limited number of independent system properties. This chapter is devoted to a further elaboration of two such fundamental concepts that belong to a class of system properties: (1) energy and (2) exergy. The main purpose of this exposition is threefold: (1) to offer a discussion of physical meanings of these concepts; (2) to present their analytical structure within the traditional thermodynamics framework; which is useful for applications; and (3) to emphasize the importance of balancing them. These topics are relevant for a variety of situations in diverse fields of interest, all identifiable in complex systems involving destruction of resources.

The notion of a concept is used to describe abstract theoretical constructs of classical thermodynamics theory. The concept of energy [1] is reintroduced in this chapter by means of a notion of a change of a system property; the concept of exergy [2] is reintroduced by means of the magnitude of an energy interaction. This magnitude would be expressed in energy units, but would be measured as an interaction extracted from the system changing the state between the given state and the state of thermodynamic equilibrium with the referent surroundings.

The first and second laws of thermodynamics should also be called the first and second laws of economics. Why? Because without them there would be no scarcity, and without scarcity, no economics. Consider the first law: if we could create useful energy as it got in our way, we would have superabundant sources and sinks, no depletion, no pollution, and more of everything we wanted without having to find a place for stuff we didn't want. The first law rules out this direct abolition of scarcity. But consider the second law: even without creation and destruction of matter-energy, we might indirectly abolish scarcity if only we could use the same matter-energy over and over again for the same purposes: perfect recycling. But the second law rules that out. So it is that scarcity and economics have deep roots in the physical world, as well as deep psychic roots in our wants and desires.

Economists have paid much attention to the psychic roots of value, but not so much to the physical roots. Generally they have assumed that the biophysical world is so large relative to its economic subsystem that the physical constraints (the laws of thermodynamics) are not binding. But they are always binding to some degree and become very limiting as the scale of the economy becomes large relative to the containing biophysical system.

Introduction

The term sustainability is used frequently now in many different contexts. For example, in the area of engineering, there have been claims of sustainable products, sustainable manufacturing, sustainable designs, and so forth. Although these uses may be well intended, they actually marginalize the term by implying that just getting better in some way is sustainable. Instead, sustainability needs to be connected to a worldview that encompasses how human society can maintain a good quality of life over a long time. Without this worldview framework, these claims of sustainable this and sustainable that ring hollow. In this context, we are inspired by the work of the authors (mostly economists with biological scientists) of the paper, Arrow et al. [1]. By starting with the well-known statement of sustainability from the UN Brundtland Report [2], they developed a measurable and workable (though controversial) criterion for sustainability.

The Brundtland UN Commission statement on sustainability says, “sustainable development is the development that meets the needs of the present generation without compromising the ability of future generations to meet their own needs.” This statement brings up many value-laden issues and at first blush seems unworkable. For example, what is a need for one person could be considered excessive consumption for another. Furthermore, who is to speak for future generations and to articulate their needs? In addition, what development means is of crucial importance, in particular, does development require growth, and if so, what kind.

Introduction

The main purpose of manufacturing processes is to transform materials into useful products. In the course of these operations, energy resources are consumed and the usefulness of material resources is altered. Each of these effects can have significant consequences for the environment and for sustainable development, particularly when the processes are practiced on a very large scale. Thermodynamics is well suited to analyze the magnitude of these effects as well as the efficiency of the resource transformations. The framework developed here is based on the exergy analysis that is reviewed in the first two chapters of this book. Also see [1–5]. The data for this study draw on previous work in the area of manufacturing process characterization, but also includes numerous measurements and estimates we have conducted. In all, we analyze 26 different manufacturing processes, often in many different instances for each process. The key process studies from the literature are as follows: for microelectronics, Murphy et al. [6], Williams et al. [7], Krishnan et al. [8], Zhang et al. [9], and Boyd et al. [10]; for nanomaterials processing, Isaacs et al. [11] and Khanna et al. [12]; for other manufacturing processes, Morrow et al. [13], Boustead [14, 15], Munoz and Sheng [16], and Mattis et al. [17]. Some of our own work includes Dahmus and Gutowski [18], Dalquist and Gutowski [19], Thiriez and Gutowski [20, 21], Baniszewski [22], Kurd [23], Cho [24], Kordonowy [25], Jones [26], Branham et al. [27, 28], and Gutowski et al. [29].

Introduction

When resources become exhausted – for whatever reasons – dearth and starvation occur. Impending crises of that sort are foreshadowed by sociological changes, and the oft-deplored phenomenon of segregation of sociological groups is one of them. However, that phenomenon may not be only a random concomitant of an economic crisis: Like a fever in an infected body, when a sick body runs a temperature, segregation may be a symptom that shows that the society is trying to survive and that it makes the best of a bad situation in expectation of better times.

Social behavior is largely dictated by the competition of sociological groups for a limited amount of resources, essentially and ultimately food. Such groups may represent social classes, or ethnic and racial groups, or religious sects, etc.

If resources are abundant and consequently prices are low, the competition is more or less friendly and relaxed, and there is room and occasion for social niceties and tolerant conduct between sociological groups. Granted that there is always competition, yet in times of abundance the competitive strategy is dictated by good will and a population finds it easy to integrate members of different groups.

When resources are scarce and therefore expensive, the competition becomes more serious, or even fierce. A new strategy – a more competitive one – may be employed by all sociological groups, and the mutual tolerance between groups is strained or altogether abandoned. Those are the conditions under which segregation occurs in a population.

Resources and Sustainability

This book is about the application of thermodynamic thinking to those new areas of study that are concerned with the human use of resources and the development of a sustainable society. Exactly what a sustainable society is, is a highly debated topic, somewhat subject to personal value preferences. However, what is not sustainable is easier to identify. For example, in Jared Diamond's popular book, Collapse [1], he identified a variety of ancient and modern societies that failed. No one would dispute this claim. Although the reasons for these failures were complex, an important and common contributing factor was an inability to manage Earth's resources and thereby meet the needs of the society. For example, the inhabitants of Easter Island apparently became consumed with building giant stone statues (called moai), which required large timbers for their construction and for their transport from the quarry to the installation site. Apparently this building process, along with the destruction of the seeds wrought by the Polynesian rats, led to the destruction of most, if not all, of their trees. One result from this was a loss of the primary building material for their canoes. Because most fish were some distance from the shore, a lack of building materials for canoes meant fewer fish to eat and the inability to move to other islands. This desperate situation ultimately resulted in the islanders resorting to cannibalism.

Energy Resources and Use Summary (Year 2008)

The status of energy resources and use in 2008 is briefly summarized in this section, with some elaboration to follow.

Current Energy Resources and Consumption

The current energy-resources and consumption situation has generally worsened relative to that at the end of 2006:

• A major concern (or opportunity?): The price of oil was growing very rapidly, from $28 in 2003 to $38/barrel in 2005 and occasionally to above $80 in 2006 and peaking at $147 in 2008, but then precipitously dropping to $40 by the end of 2008.

• The peak price is 1–2 orders of magnitude higher than the cost of extraction, possibly meaning that financial speculation is overwhelming supply and demand and all technical improvements.

• In 2007, world primary energy-resources use rose by 2.4%, with the increase rate slightly dropping (Fig. 8.1), but is likely to rise again soon, as the large developing countries in Asia keep improving their standard of living; China's rose by 7.7% (lowest since 2002), India's by 6.8%, and the United States' by 1.6%, Japan's dropped by 0.9%, and EU's dropped by 2.2% (EU is the European Union).

• The reserves-to-production (R/P) ratio remains rather constant: ~40 for oil, ~60 for gas, and 200+ for coal, and mostly rising (Figs. 8.2 and 8.3)! There are probably sufficient oil and gas for this century and coal for two or more.

• Tar sands and oil shales are becoming more attractive and available in quantities probably exceeding those of oil and gas.

• […]

Introduction

For a model of a production process to be valid in the real world, it has to take proper account of the principles of thermodynamics. Production models in economics are no exception. The conservation of mass requires that proper attention be paid to the mass balance between inputs and outputs entering and leaving a given production process. An increase of entropy implies the generation of process waste in the production phase and the reduction in the purity of materials in the use and end-of-life (EoL) phases. Because process waste is generated in the production phase, it should be classified as an output if the mass balance between inputs and outputs is to be established. The reduction in the purity of materials in the use phase is relevant for materials made of polymers, such as paper, textile, and plastics, whose chemical bindings loosen over time.

On the other hand, for metals such as iron, copper, or aluminum, such a decline in quality in the use phase will not occur [except for possible corrosions (oxidization)] because these metals are elements. In fact, it is not the use phase but the EoL phase in which a serious reduction in the quality of metal materials can occur because of the mixing-up of diverse metal elements or the “contamination” of pure elements with other elements in minor quantities (tramp elements).

Introduction

In this chapter, we develop several models for the materials-recycling process. The focus is on the separation of materials from a mixture. This problem can be modeled by using the principles of thermodynamics, particularly the concept of mixing entropy, as well as by using some of the results from information theory. In doing this calculation we will find, from a thermodynamic point of view, that the theoretical minimum work required for separating a mixture is identical to the work lost on spontaneous mixing of the chemical components. In other words, the development in this chapter in conjunction with the results from previous chapters will allow us to track both the degradation in materials values as they are used and dispersed in society as well as the improvement and gain as materials are restored to their original values. Of course, this restoration does not come for free, and so we also look at the losses and inefficiencies involved in materials recycling. This approach allows us to look at the complete materials cycle as it moves through society and to evaluate the gains and losses at each step. The chapter starts with the development of the needed thermodynamics concepts and then moves on to the application of these ideas. This chapter also introduces an alternative way of looking at the recycling problem by using information theory.

Introduction

The notion that technological progress leads to reduced demand of materials and energy to manufacture products and deliver services is known as dematerialization [1]. The conventional conception of dematerialization views products and services as static, and from this perspective technological progress can but mitigate the impact per product produced. A demand for increased functionality and performance, however, induces changes in products. Automobiles, computers, and cell phones, for example, have become significantly more complex over the past two decades. A more complex design generally implies tighter tolerances in materials, parts, and manufacturing processes. Semiconductor, nanotechnology, and pharmaceutical manufacturing in particular require chemicals and processing environments that are much purer than traditional industries. Viewing this trend through the lens of thermodynamics, one can assert that the entropy of many products has been decreasing as a function of increasing sophistication. The second law of thermodynamics dictates that the entropy of an isolated system cannot decrease. A purified separation has lower entropy than a mixed one; thus purification implies interaction with the external world. In practice, this interaction is subjecting the system to processes that involve net inflows of energy, e.g., distillation. Purification in practice requires the input of energy, suggesting that increasing complexity should come at a cost of additional processing. This additional processing requires additional secondary energy and materials to attain the desired low-entropy form, a trend we call secondary materialization [2].

Human production activity is based on natural resources. Their usefulness results from the ability to be transformed into useful products necessary for humans. That ability may be evaluated by means of the laws of thermodynamics that express not only the conservation of energy but also its tendency to be dissipated. The dissipation of energy (resulting in entropy generation) decreases its usefulness and reduces its ability to be transformed into useful products. The mentioned ability may be evaluated by means of the maximum work attainable in a reversible transition to the equilibrium with the environment embracing that part of nature that belongs to the area of human production activity. That quantity is usually called “exergy.”

A considerable part of the natural resources utilized by humans belongs to the nonrenewable ones (organic and nuclear fuels, ores of metals, inorganic minerals). The usefulness of nonrenewable resources results from their chemical composition. The chemical exergy can be accepted as a general quality measure of the mentioned resources because it expresses the maximum work attainable during the transition to equilibrium with a dead environment.

However, equilibrium with the natural environment is not possible, because it does not appear in the real natural environment. As proved by Ahrendts [1], the concentration of free oxygen in an equilibrium environment would be very small because the prevailing part of oxygen would be bound with nitrogen in nitrates. Fortunately the formation of nitrates is kinetically blocked, and they appear very seldom in nature.

Introduction

In the 1930s, Wassily Leontief was putting the finishing touches on his development of the input-output (IO) matrices of the U.S. economy, just in time for its strategic use in converting our industry to a war footing. His process allowed the direct and indirect demands of industry to be estimated for a given gross national product (GNP). The government stated its concepts of the needs for the items of war in terms of the numbers of airplanes, tanks, guns, explosives, and so forth, for each of the four or five years they expected the war to last. Leontief was able to determine, for this final bill of goods, the flows of steel, aluminum, energy, and such needed from each industry, directly and indirectly [1]. Then these flows were compared with the capital stocks needed in these industries to meet the wartime demands. What they found was that the output of war material and energy plus those of personal consumption was not possible given then-current capacities in any of the major sectors. Two major endeavors were soon undertaken: massive new construction programs in steel production and shipbuilding, including conversion of many industries to the production of military items, for example, the auto companies converting to the production of military vehicles, and the substantial reduction of personal consumption of cars, gasoline, tires, and certain kinds of food. How did he do it?

Introduction

In this chapter we briefly survey some of the other important features of the flows through turbomachines. We begin with a section on the three-dimensional characteristics of flows, and a discussion of some of the difficulties encountered in adapting the cascade analyses of the last chapter to the complex geometry of most turbomachines.

Three-Dimensional Flow Effects

The preceding chapter included a description of some of the characteristics of two dimensional cascade flows in both the axial and radial geometries. It was assumed that the flow in the meridional plane was essentially two-dimensional, and that the effects of the velocities (and the gradients in the velocity or pressure) normal to the meridional surface were neglible. Moreover, it was tacitly assumed that the flow in a real turbomachine could be synthesized using a series of these two-dimensional solutions for each meridional annulus. In doing so it is implicitly assumed that each annulus corresponds to a streamtube such as depicted in figure 4.1 and that the geometric relations between the inlet location, r1, and thickness, dr1, and the discharge thickness, dn, and location, r2, are known a priori. In practice this is not the case and quasi three-dimensional methods have been developed in order to determine the geometrical relation, r2(r1). These methods continue to assume that the streamsurfaces are axisymmetric, and, therefore, neglect the more complicated three-dimensional aspects of the flow exemplified by the secondary flows discussed below (section 4.6).