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In this paper, a review of exergy and improvement potential (IP) of solar thermal systems is presented. The review includes exergy analysis of photovoltaic thermal (PVT) systems, solar drying systems and solar collectors. Solar collectors, which are the most essential components of solar thermal systems, receive solar energy and convert it into thermal energy. Since the solar/PVT collector system is an essential component when the design of sustainability is considered, exergy analysis, which provides a more representative performance rating. In addition, a theoretical and experimental performance of hybrid photovoltaic thermal/thermoelectric (PVT/TE) air collector is investigated. A steady-state thermal analysis of a hybrid PVT/TE air collector is developed to predict air outlet and photovoltaic (PV) temperatures. The predicted results are in close agreement with the experimental study. The percentage error of air outlet and PV temperatures between theoretical and experimental value is 1.1% and 2.6% respectively. On the other hand, the simulated model is then used to study the performances of a hybrid PVT/TE air collector using exergy analysis for the mass flow rate ranging between 0.001 kg/s to 0.15 kg/s and a solar radiation of 600 W/m2. The effect of mass flow rate on exergy efficiency and an advance prospective are observed. The optimum exergy efficiency of PVT/TE obtained is relatively 0.38. In addition, IP is proposed in this study. • The theoretical approach on the hybrid photovoltaic thermal/thermoelectric (PVT/TE) air collector is developed. • The predicted results are in close agreement with the experimental study. • The exergy efficiency of hybrid PVT/TE air collector obtained is superior compared PVT air collectors. • The exergy efficiency of hybrid PVT/TE air collector obtained is 38%. • The exergy efficiency of PVT air collector of review study obtained is 4–18%. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a review of the exergy and sustainability index of solar thermal systems. The review includes exergy analyses of solar collectors, solar drying systems and photovoltaic thermal (PVT) systems. Solar collectors, the most essential components of solar thermal systems, receive solar energy and convert it into thermal energy. The PVT collector is a popular means of harvesting solar energy. A PVT collector can generate electrical and thermal energies simultaneously. Experimental and theoretical approaches for a PVT air collector with a ∇-corrugated absorber are investigated in this study. A steady-state energy analysis of the PVT air collector is performed to predict photovoltaic (PV) and air outlet temperatures. Experimental results are in close agreement with the results of the theoretical study. The percentage errors of PV and air outlet temperatures between experimental and theoretical values are 5.49% and 3.75%, respectively. The PVT exergy efficiency of the PVT air collector with a ∇-corrugated absorber is 13.36% and 12.89% for the theoretical and experimental study, respectively. Furthermore, a sustainability index is proposed. The sustainability index of the PVT air collector is 1.168 and 1.148 for the theoretical and experimental study, respectively. Highlights • The theoretical approach of photovoltaic thermal (PVT) air collector with ∇-corrugated absorber is presented. • The predicted results are consistent with the results obtained from the experiments. • The exergy and sustainability index for various mass flow rates and solar radiations are obtained. • The exergy and sustainability index of solar thermal systems are reviewed. [ABSTRACT FROM AUTHOR]

Photovoltaic–thermal (PVT) collectors can generate electrical and thermal energy simultaneously. The combination of these two technologies can reduce the required space, time installation and use of materials. PVT air collector present increased total efficiency by increasing solar radiation amount. This review presents the concepts and descriptions, as well as previous works conducted on thermoelectric (TE). A theoretical study of PVT-TE air collectors is also performed. Mathematical models are proposed and solved using iterative process based on the matrix inversion method. An improvement in energy yields can be obtained using TE solar collector technology because TE devices increase the energy conversion efficiency of the system. The annual cost (AC) and annual energy gain (AEG) of PVT-TE air collectors are determined. The cost–benefit ratio or AC per AEG (AC/AEG) is presented for different combinations of mass flow rate and number of TE to increase the feasibility of users in selecting the optimal design features that correspond to minimum AC/AEG. [ABSTRACT FROM AUTHOR]