On Exergetics, Economics and Optimization of Technical Processes to Meet Environmental Conditions

and Tribus, 1962), which is also named exergoeconomics (Bejan et al, 1996) and exergonomics (Yantovskii, 1994). The concept of utility is a central concept in macroeconomics. Utility is also closely related to exergy, and an exergy tax is an example of how exergy could be introduced into macroeconomics. This paper introduces and clarifies important concepts in the development of a sustainable engineering. An engineer designing a system is expected to aim for the highest possible technical efficiency at a minimum cost under the prevailing technical, economic and legal conditions, but also with regard to ethical, ecological and social consequences. Exergy is a concept that makes this work a great deal easier. Thus, exergetics offers a unique insight where losses and possible improvements can be determined, and Life Cycle Exergy Analysis (LCEA) is suggested as a method to better meet environmental conditions. Optimization pervades the fields of science, engineering, and business, which is concerned with finding the best system among the entire set by efficient quantitative methods. Computing makes the selection feasible and cost efficient. But to employ them requires, firstly critical analysis of the process or design, secondly insight as to what the appropriate performance objectives are, i.e., what is to be accomplished, and thirdly use of past experience, sometimes called “engineering judgment.” Exergy is also a useful concept in economics. In macroeconomics exergy offers a way to evaluate resource depletion and environmental destruction by means of an exergy tax. In microeconomics exergy has fruitfully been combined with cost-benefit analysis to improve the design. By minimizing Life Cycle Cost (LCC) we find the best system due to the prevailing economic conditions, and by minimizing the exergy losses, we also minimize environmental effects. However, the design is much more than using proper tools and performing a correct optimization. In a real system design consideration for environmental, social and ethical consequences must also be taken. Good design methods should also make maximum use of the designer’s skills, knowledge, and experience. (Sama, 1995) In addition, a designer should also have a basic knowledge in ecology and sociology, as well as ethics and morals. (Wall, 1995) INTRODUCTION When constructing a system, the goal is to attain the highest possible technical efficiency at the lowest cost within the existing technical, economical and legal constrains. The analysis also includes different operating points (temperatures, pressures, etc.), configurations (components, flow charts, etc.), purpose (dual purpose, use of waste streams, etc.), and environments (global or local environment, new prices, etc.). Designing efficient and cost effective systems, which also meet environmental conditions, is one of the foremost challenges that engineers face. In the world with finite natural resources and large energy demands, it becomes increasingly important to understand the mechanisms which degrade energy and resources and to develop systematic approaches for improving systems and thus also reducing the impact on the environment. Exergetics combined with economics, both macroand microeconomics, represents powerful tools for the systematic study and optimization of systems. Exergetics and microeconomics forms the basis of thermoeconomics (Evan Usually the design and operation of systems have many solutions — sometimes an infinite number. By optimizing the total system, we always find the best system under the given conditions. Some of the general engineering optimization