Introduction and Fundamentals

Abstract

This chapter discusses the relevance of environmental effects caused by humans and the concept of sustainable development. Many of these effects take place on a global scale. Thus they are relevant for the Earth system (Steffen et al. 2005) and presently constitute a major challenge for human societies. The second section deals with the definition of systems, their balances, and their properties with special emphasis on dynamic and feedback situations. In the third section, it is described how systems respond to internal processes and to changes of their surroundings. Classical thermodynamics distinguishes between different kinds of energies that can be interconverted without altering the sum of all energies. However, different kinds of energy have not the same quality and low-level energy cannot be completely transformed to higher levels. Second-law analyses using the concepts of entropy and exergy are required to describe the efficiency of these transformations. Finally, non-equilibrium thermodynamics devoted to real systems far away from equilibrium, where fluctuations and instability are of great importance, are briefly discussed.