Teaching Basic Thermodynamics for Energy Efficiency: A Digest of the Theoretical Basis of the Exergy Concept
1993 (English)Conference paper (Refereed)
Exergy is a general measure of the maximal work yield of a system, applicable to general processes involving interactions, either internally or with other systems, as well as constraints. Exergy is a key thermodynamical concept in many methods for the improvement of energy efficiency in technical as well as societal systems; it is, e.g., the basis for the idea of second law efficiency. It therefore plays a significant rôle in the transformation to the energy efficient society based on renewable energy sources. Although exergy is a fundamental quantity in the theory of conversions of matter and energy, it is often inadequately treated in thermodynamics text-books. This paper describes some of those key features of exergy as a thermodynamic concept that are rarely included in courses on thermodynamics, with examples of derivations of exergy formulas in general as well as in some special cases. It also describes the rôle of exergy in a physical world view, in particular the origin of exergy.
Many thermodynamic processes in nature involve not only simple conversion of energy and materials but also formation or breakdown of structure. Some kinds of structure formation or breakdown can be conveniently described in information theory terms. Information theory, dealing with information as a quantitative concept, was from the beginning close to physical theory, with entropy as a common concept. Information theory is closely tied to statistical mechanics, the microscopic theory of thermodynamics. To elucidate and demarcate the general scope of the exergy concept, I describe how the essentially physical quantities work and exergy can be tied to information-theoretical quantities.
Place, publisher, year, edition, pages
Research subject Environmental and Energy Systems
IdentifiersURN: urn:nbn:se:kau:diva-24165OAI: oai:DiVA.org:kau-24165DiVA: diva2:597932
K. Blum & L. Broman, eds., Progress in Solar Energy Education, Volume 2. Proceedings of the Second International Symposium on Renewable Energy Education, Oldenburg, Germany, 10-11 June 1992. Carl von Ossietzky University, Oldenburg 1993, pp. 28-34