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This paper presents an experiment and an examination of the performance of a mixed solar dryer with forced convection, which has been used to dry tomatoes. The studied system is composed of a photovoltaic-thermal air collector (PV/T) and drying room. Actually, the air flux enters in the aluminium tubular canals located under the PV panel and spreads simultaneously into an upper gap. Consequently, it provides heat exchange in both faces of the panel PV which helps to cool the photovoltaic cells and to carry the thermal energy to the drying room. What make this prototype important and original is that it provides an economic gain for farmers who previously used natural drying techniques. It grants them the chance to conserve the dried tomatoes for longer periods and to reduce the loss of crops. Furthermore, it provides more electrical energy supplies for the rural areas. Tomatoes were divided into two trays and dried with the forced convection mixed solar dryer. After that, a comparison was established with a naturally dried sample. Using the realized prototype, product moisture content dropped from 91.94 (%) to 22.32 (%) for tray 1 and to 28.9 (%) for tray 2, by against it dropped only to 30.15 (%) for open sun dryer. It is noted that the drying temperature is improved and the quality is enhanced. The experimental tests are carried out at the Laboratory of Electromechanical Systems in the National Engineering School of Sfax in Tunisia during September 2015.

PV/T systems are an emerging technology for the simultaneous production of electrical and thermal energy. In this paper, we present an experimental device modified with an arrangement of aluminum square tubes to remove thermal heat from the system and increase its electrical efficiency. A 1D analysis allowed prediction of the heat transfer in the solid components. Moreover, a 3D simulation allowed visualization of the temperature distribution in the prototype. The simulations considered the surrounding temperature, the solar irradiance and the airflow velocity inside the square tubes. The glass temperature, PV cell temperature and the outlet airflow temperature were logged. The study was performed at a low airflow (0.5 m/s) and at a high airflow (2 m/s); for both experiments, the maximum solar irradiance was 800 W/m2 and the heat fluxes were calculated. The time constant was shorter for the experiment at low airflow, because the airflow increased by 63.2% at 5400s. At a high airflow, it took 9100 s to achieve the 63.2% of the maximum increase, and the difference between the outlet temperature and the temperature of the surrounding air was significantly reduced. At 0.5 m/s and 2 m/s the PV cell reached a maximum temperature of 75 °C and 59 °C, respectively. The maximum difference in temperature between the two experiments was 20 °C. The best thermal average efficiency was 42.5%, corresponding to the high airflow experiment. Furthermore, based on the favorable air outlet temperature, at this flow rate, the outlet air could be used for drying in a subsequent process.

In this research, we present an experimental study and a 2D simulation investigation of a hybrid photovoltaic/thermal (PV/T) collector. The proposed model is used to study the thermal effeciency of PV/T air collector and to discuss the air distribution inside the channel of collector. A 2D temporal heat transfer model coupled to laminar flow was solved by software COMSOL Multiphysics. The model considers the air temperature, solar irradiation, and mass flow rate. The simulation shows a good agreement with experimental data logged for the glass temperature, air gap temperature, PV temperature, air temperature inside the channels (PV/T system) and the outlet temperature. The experimental results are well described by the simulation and the numerical methodology can be used to calculate the parameters characterizing the thermal behavior of the collector. Using the realized prototype, thermal efficiency increases with increases of mass flow rate. Further, the PV panel temperature decrease with increases of mass flow rate.