We present a new approach for solving phase equilibria problems in multicomponent systems together with several applications. A mathematical framework is developed that provides a method for generalizing the thermodynamics of a finite-component system to that of a system with an infinite number of components—a polydisperse system. Two new functions, the mole fraction distribution function and the mole fraction density function, play a key role in our method. The phase equilibria conditions are written in terms of these functions and are formally solved. We illustrate the utility of our approach by solving, for a polydisperse generalization of the van der Waals model, three phase-equilibria problems: (1) the fractionation of a polydisperse impurity dissolved in a solvent; (2) the shift of the critical temperature and density due to the presence of a polydisperse impurity; (3) the calculation of the cloud-point surface and critical point of a completely polydisperse system.

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The idea of combining photovoltaic and solar thermal collectors (PVT collectors) to provide electrical and heat energy is an area that has, until recently, received only limited attention. Although PVTs are not as prevalent as solar thermal systems, the integration of photovoltaic and solar thermal collectors into the walls or roofing structure of a building could provide greater opportunity for the use of renewable solar energy technologies. In this study, the design of a novel building integrated photovoltaic/thermal (BIPVT) solar collector was theoretically analysed through the use of a modified Hottel-Whillier model and was validated with experimental data from testing on a prototype BIPVT collector.The results showed that key design parameters such as the fin efficiency, the thermal conductivity between the PV cells and their supporting structure, and the lamination method had a significant influence on both the electrical and thermal efficiency of the BIPVT. Furthermore, it was shown that 1

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