Solar thermal power generation using water as a Heat Transfer Fluid (HTF) has gained interest recently, due to its ability to generate steam directly from the receiver tube. In this paper, a new theoretical model of receiver called Concentric Parabolic Trough Receiver (C-PTR) for direct steam generation is presented. The proposed model consists of Phase change material (PCM) sandwiched between two concentric cylindrical tubes. Binary Solar Salt commercially known as ‘molten salt’ (60% NaNO3 + 40% KNO3), is used as the PCM for analysis. The PCM absorbs the solar thermal energy incident on the C-PTR and supplies heat at a steady rate to heat transfer fluid, to avoid fluctuations (due to sudden climate changes and passing clouds) in the steam generation in the receiver tube. A theoretical model is developed and the influence of various parameters such as inlet temperature, concentration ratio, mass flow rate and ambient temperature is studied. The theoretical results show that the thermal efficiency of C-PTR is about 50% for a mass flow of 0.3 kg/s and with an optical efficiency of 0.74. From the results it can be concluded that the proposed C-PTR system is feasible and could be used in the parabolic trough system for direct steam generation.
