Exergy analysis of solar radiation processes - Solar Energy Sciences and Engineering Applications - page 7

Exergy analysis of solar radiation
processes
Ryszard Petela
Technology Scientific Ltd., Calgary, Alberta, Canada
2.1 INTRODUCTION
Radiation energy can be converted to work, heat, chemical energy or electricity.
Direct conversion to work is so far not well developed, but potential examples
are the idea of sailing in space via photon wind, a combination of gravity and
buoyancy in a solar chimney power plant or utilization of radiation pressure. By
conversion to heat the enthalpy of any operating fluid is usefully increased. Con-
version to chemical energy is photosynthesis and conversion to electricity occurs in
photovoltaic.
The present chapter contains problems of engineering thermodynamics of thermal
radiation and thus is mainly based on the topic by Petela (2010), until now the only one
written on this subject. The chapter outlines the fundamentals of examining processes
in which radiation takes place. Beside traditional methods of energy analysis of such
processes, the full thermodynamic analysis, including the exergy analysis, is discussed
and illustrated by examples of some typical utilization processes of solar radiation.
The analysis is preceded by a basic description of exergy which is a property of any
matter.
Everything which has mass is called matter . The matter appears in substantial or
non-substantial forms. Mass is a property of matter which determines momentum and
the gravitational interactions of bodies. Substance is matter for which the rest mass is
not equal to zero. Thus, the substance is the macroscopic body composed of elemental
particles (atoms, molecules). The matter for which the rest mass equals zero (e.g.
radiation photons) appears in the form of different fields; e.g. fields of electromagnetic
waves (radiation), gravity fields, surface tension fields, etc.
Substance can be the object of the conservation equation. Non-substantial
matter (called sometimes field matter ) can also be considered as the component
in processes of energy conversion; however it does not fulfill the matter conser-
vation equation. Processes considered here are composed of substance and field
matter.
The chapter develops a methodology of examining thermodynamic processes
under the assumption that the reader is familiar with the fundamentals of engineering
thermodynamics and heat and mass transfer. The details of mechanisms of the consid-
ered processes and installations are discussed in other parts of the topic together with
relevant references.