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Driven by the importance of optimizing energy systems and technologies, the field of exergy analysis was developed to better illuminate process inefficiencies and evaluate performance. Exergy analysis provides important information and understanding that cannot be obtained from energy analysis. The field of exergy analysis is well formulated and understood except for thermal radiation (TR) heat transfer. The exergy flux, or maximum work obtainable, from TR has not been unambiguously determined. Moreover, many thermodynamic textbooks are misleading by incorrectly implying that the entropy and exergy transport with TR is calculated by using the same expressions that apply to heat conduction. Research on the exergy of TR was carried out by Petela. However, many researchers have considered Petela's analysis of the exergy of TR to be irrelevant to the conversion of TR fluxes. Petela's thermodynamic approach is considered irrelevant because, others argue, that it neglects fundamental issues that are specific to the conversion of fluxes, issues that are unusual in the context of exergy analysis. The purpose of the research in this thesis is to determine, using fundamental thermodynamic principles, the exergy flux of TR with an arbitrary spectrum and its relevance to solar radiation (SR) conversion. In this thesis it is shown that Petela's result can be used for the exergy flux of blackbody radiation (BR) and represents the upper limit to the conversion of SR approximated as BR. The thesis shows this by resolving a number of fundamental issues: (1) Inherent Irreversibility; (2) Definition of the Environment; (3) Inherent Emission; (4) Threshold Behaviour; (5) Effect of Concentrating TR. This thesis also provides a new expression, based on inherent irreversibility, for the exergy flux of TR with an arbitrary spectrum. Previous analysis by Karlsson assumes that reversible conversion of non-blackbody radiation (NBR) is theoretically possible, whereas this thesis presents evidence that NBR conversion is inherently irreversible. In addition the following conclusions and contributions are made in the thesis: (1) Re-stated the general entropy and exergy balance equations for thermodynamic systems so that they correctly apply to TR heat transfer. (2) Provided second-law efficiencies for common solar energy conversion processes such as single-cell Photovoltaics. (3) Showed that Omnicolor (infinite cell) conversion, the widely held ideal conversion process for SR, is not ideal by explaining its non-ideal behaviour in terms of exergy destruction and exergy losses. (4) Presented an ideal (reversible) infinite stage thermal conversion process for BR fluxes and presented two-stage thermal conversion as a practical alternative. (5) Showed that Prigogine's minimum entropy production principle cannot be used as a governing principle in atmospheric modeling, and that in general, it may have little significance. (6) Presented a graybody model of the planet that may prove useful in understanding the thermodynamics of the Earth system. (7) Showed that the expression derived from the Clausius equality for reversible processes is applicable, whereas the statement for irreversible processes is not applicable, when there is significant heat transfer by TR. (8) Showed that the 4/3 coefficient in the BR entropy expression can be obtained by simply using the concept of equilibrium and the experimentally observable relationship for BR energy (energy x T⁴). / Graduate

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The Bose-Einstein distribution is derived, and from this the mean values and fluctuations of the thermodynamic quantities describing a volume V of black body radiation at absolute temperature T, are calculated. The problem of the energy fluctuation of a body of emissivity ε in thermodynamic equilibrium with a volume of black body radiation, is considered from a statistical approach. The result var E = kT ²C , known to be correct from thermodynamics, is obtained. The zero point energy difficulty in the mean energy of the radiation is discussed in detail. Arguments are presented supporting the inclusion of the zero point energy in the thermal radiation theory. The problem of the number of distinguishable levels that can be obtained from a certain signal power in a resonator is discussed in this section. Finally the results of the theory above are employed to determine the ultimate sensitivity of radiation detectors. Care is taken to isolate factors which are not fundamental properties of the detector, from the treatment of the detector sensitivity. A bolometer and a phototube, energy and quantum detectors respectively, are discussed in detail. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

In order to analyse the radiant heat transfer characteristics of a concave source, two vital concepts must be clearly understood. The first is called the apparent emissivity Ea and is a function of both the local total emissivity E and of the geometry of the source. Although the total emissivities of ordinary substances range between zero and one, the two extremeties never occur. Surface emissivities which approach these values in the limit, must be created mechanically from materials in the range 0

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