Although the thermodynamic advantages of using solar energy to replace the bled off steam in the regeneration system of Rankine cycle coal fired power stations has been proven theoretically, the practical techno/economic feasibility of the concept has yet to be confirmed relative to real power station applications. To investigate this concept further, computer modelling software “THERMSOLV” was specifically developed for this project at Deakin University, together with the support of the Victorian power industry and Australian Research Council (ARC). This newly developed software simulates the steam cycle to assess the techno/economic merit of the solar aided concept for various power station structures, locations and local electricity market conditions. Two case studies, one in Victoria Australia and one in Yunnan Province, China, have been carried out with the software. Chapter one of this thesis defines the aims and scope of this study. Chapter two details the literature search in the related areas for this study. The thermodynamic concept of solar aid power generation technology has been described in chapter three. In addition, thermodynamic analysis i.e. exergy/availability has been described in this chapter. The “Thermosolv” software developed in this study is detailed in chapter four with its structure, functions and operation manual included. In chapter five the outcomes of two case studies using the “Thermosolv” software are presented, with discussions and conclusions about the study in chapters 6 and 7 respectfully. The relevant recommendations are then made in chapter eight.

The solvent-induced swelling behaviour of Victorian brown coals was examined in detail to probe the bonding mechanisms in very low rank coals (in this case Victorian brown coal). Correlation of solvent properties with differences in observed swelling behaviour were interpreted in terms of the coal structure, and means of predicting the observed behaviour were considered. Modification of the coal structure via physical compression (briquetting), chemical digestion, thermal modification, and functional group alkylation was used to further elucidate those structural features which govern the swelling behaviour of Victorian brown coals. Briquette weathering (i.e. swelling and disintegration of briquettes when exposed to variations in humidity and temperature) was examined by making alterations to briquette feed material and observing the effects on swelling in water. The application of solubility parameter alone to prediction of coal swelling was rejected due to the many exceptions to any proposed trend. Brown coal swelling showed a minimum when the solvent electron-donor number (DN) minus its electron-acceptor number (AN) was closest to zero, i.e. when DN and AN were of similar magnitude. The degree of swelling increased either side of this point, as predicted by theory. In contrast to the solubility parameter approach (which suffers from the uncertainty caused by specific interaction between coal and solvent), the electron donor/acceptor approach is about specific interactions. It was concluded that a combination of total and three-dimensional solubility parameters and solvent electron donor/acceptor numbers may be used to predict solvent swelling of unextracted brown coals with some success. Solvent access to chemically densified coal was found to be insensitive to a reduction in pore volume, and chemical effects were dominant. Thermal modification of the digested coal resulted in reduced swelling for all solvents, indicating that the structure had adopted a minimum energy configuration due to decarboxylation and replacement of hydrogen bonds with additional covalent bonds. Swelling of oxygen-alkylated coals demonstrated that the more polar solvents are able to break relatively weak hydrogen bonded crosslinks. The large difference between the rate and extent of swelling in water (and hence weathering) of Yallourn and Morwell briquettes was shown to be almost entirely attributable to exchanged magnesium. Magnesium exchange significantly increases the rate and extent of swelling of Yallourn coal. It was also shown that the swelling of briquettes due to uptake of water by magnesium-exchanged coals is reduced significantly with controlled ageing of the briquettes. The solvent swelling behaviour of Victorian brown coals is consistent with the notion that coal is a both covalently and non-covalently crosslinked and entangled macromolecular network comprising extractable species, which are held within the network by a wide range of non-covalent, polar, electron donor/acceptor interactions. Solvents capable of significant extraction of whole brown coals are also capable of significant swelling, but not dissolution, of the macromolecular coal network, which supports the view that the network is comprised of both covalent and ionic bonding. Victorian brown coals have also been shown to exhibit polyelectrolytic behaviour due to a high concentration of ionisable surface functionalities.