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Abstract: This paper presents a detailed finite-volume model of a concentrating photovoltaic/thermal (PVT) solar collector. The PVT solar collector consists in a parabolic trough concentrator and a linear triangular receiver. The bottom surfaces of the triangular receiver are equipped with triple-junction cells whereas the top surface is covered by an absorbing surface. The cooling fluid (water) flows inside a channel along the longitudinal direction of the PVT collector. The system was discretized along its axis and, for each slice of the discretized computational domain, mass and energy balances were considered. The model allows one to evaluate both thermodynamic and electrical parameters along the axis of the PVT collector. Then, for each slice of the computational domain, exergy balances were also considered in order to evaluate the corresponding exergy destruction rate and exergetic efficiency. Therefore, the model also calculates the magnitude of the irreversibilities inside the collector and it allows one to detect where these irreversibilities occur. A sensitivity analysis is also performed with the scope to evaluate the effect of the variation of the main design/environmental parameters on the energetic and exergetic performance of the PVT collector. [Copyright &y& Elsevier]

Abstract: The paper is focused on the dynamic simulation of a Photovoltaic/Thermal collector (PVT) integrated in a high-temperature Solar Heating and Cooling (SHC) system. The system is based on the following main components: concentrating parabolic PVT (photovoltaic thermal) collectors, a double-stage LiBr-H2O absorption chiller, storage tanks, auxiliary heaters, balance of plant devices. The PVT is made-up by a parabolic dish concentrator and a triple-junction receiver. The polygeneration system provides electricity, space heating and cooling and domestic hot water for a given building, whose simulation is also included in the model. In particular, PVT produces electric energy, which is in part consumed by the building loads (lights and equipments), in part by the system parasitic loads, whereas the eventual excess is sold to the public grid. Simultaneously, the PVT provides the heat required to drive the absorption chiller. The system was simulated by means of a zero-dimensional transient model, that allows the evaluation of temperature profiles and also heat/electrical energy flows for whatever period of the year. It is also possible to evaluate the overall energetic and economic performance on whatever time basis (day, week, month, year, etc.). The economic results show that the system under investigation can be profitable, if a proper funding policy is available. The paper also includes an extensive parametric analysis aiming at evaluating the set of design and operating parameters (solar field area, tank volumes, set point temperatures, etc.) that maximize the energetic and/or economic performance of the system. [Copyright &y& Elsevier]

This paper presents a novel dynamic simulation model for the analysis of a hybrid turboexpander system coupled with innovative high-vacuum solar thermal collectors. The model is developed in MatLab and it is able to dynamically calculate the energy, exergy, environmental, and economic performances of the investigated system, by taking into account the hourly fluctuation of thermodynamic and economic parameters (e.g. electricity cost, natural gas temperature, and flow rates, etc.). In addition, a computer-based Design of Experiment (DoE) approach was implemented for achieving the optimal design of the proposed system. A suitable case study is presented in order to show the capabilities of the developed simulation tool. Conventional and non-conventional decompression systems located in the weather zone of Messina (South-Italy) are investigated with the aim of assessing the optimal system configuration. By means of the computer-based DoE analysis, the optimal values of several design parameters (such as the number of solar thermal collectors, the volume of the hot water storage tank, and the size of the water loop pump) are calculated. Numerical results show significant primary energy savings (1.36 TWh/year) and avoided carbon dioxide emissions (348 t CO2 /year). From the economic point of view, a feasible simple pay-back period of 4.51 years is achieved. The destroyed exergy of the system components are calculated, obtaining the highest value for the turbo-expander, equal to 12.0 TWh/year. • Dynamic modelling and simulation of natural gas turbo-expander system. • Energy, exergy and economic analysis of the turbo-expander system coupled to solar thermal collector field. • DoE analysis for the optimization of the solar field. • Analysis of a case study of pressure reduction station. • Confirmed system feasibility by achieved energy, economic and environmental results. [ABSTRACT FROM AUTHOR]