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Solar water heaters represent a crucial component of sustainable energy systems, offering the potential to reduce energy costs and limit carbon emissions. This study focuses on the investigation of energy and exergy efficiency enhancement in evacuated tube solar water heaters deployed in the hot climate of Dezful, Iran. Specifically, the study evaluates the impact of engine-oil as a circulation fluid within copper U-tubes positioned inside evacuated tubes, with the addition of TiO2 nanoparticles in two concentrations (0.2 mass% and 0.4 mass%). Additionally, the study assesses the effectiveness of a metallic twisted tape insert within the U-tubes to augment the heat transfer rate, with the aim of improving the overall efficiency and performance of the system. In the assessments, the thermal efficiency diagram was divided by three phases and the behavior of each one was elaborated. As results, employing metallic-insert leads to 1.5 °C more water temperature. Moreover, 5.6 °C difference between 0.4 mass% TiO2 + insert and the base case was observed in the evening which results in 24.4% and 25.52% higher thermal efficiency and exergy efficiency, respectively. [ABSTRACT FROM AUTHOR]

Heat transfer enhancement in thermal systems is one of the most important efforts of researchers. Adding nanoparticles to circulating fluid is an effective way to increase the heat transfer rate, while its effect on pressure drop may be positive or negative in various cases. In this paper, both thermal and hydrodynamic aspects of flowing a TiO2/water nanofluid were considered with concentrations of 0.05, 0.1, 0.2, 0.5, and 1 mass percentages. The nanofluid was streamed through a helical coiled path, under a constant heat flux and different flow rates. The thermal characteristics are followed by calculations of Nusselt number (Nu), convective heat transfer coefficient, and heat transfer enhancement (HTE%). Accordingly, the utmost increase in Nusselt number was found as 29.8 and 36.5% for the concentration of 1 mass%, in laminar and turbulent flows, respectively. The pressure drop was assessed by means of friction factor and drag reduction percentage (DR%), so that in the lowest concentration and the lowest Reynolds number, the maximum DR% occurred as 6.4%. To have a better understanding of the system, the pumping power is reported against HTE% amounts. [ABSTRACT FROM AUTHOR]

For a long time, electricity is supplied by means of firing the fossil fuels in thermal power plants. Now, it is well-known that the activity has many environmental and health issues, which are sharply menace the future of earth and humanity. Photovoltaic (PV) system is one of the popular renewable types of energy generation, which is available in most parts of the earth. Unfortunately, temperature rise in a PV module, leads to a significant reduction in its electrical efficiency. In this paper, two methods of wind blowing and mounting fins are considered separately and simultaneously, to overcome the mentioned weak-point. The wind velocity is set to 2 km/h. So, four cases are assessed, experimentally. As results, it was revealed that wind blowing of 2 km/h is more effective than fins in cooling PV module, so that, it can create more than 15 °C lower temperature than mounting fins. The mentioned temperature reduction leads to enhance the electrical efficiency and output power by 2.4% and 21.7%, respectively. In order to show the accuracy of results, all experimental outcomes in electrical efficiency were compared with the analytical formula. Moreover, the environmental evaluation of commissioning a 10 kW PV power plant with the proposed cases are reported, too. [ABSTRACT FROM AUTHOR]

Nowadays, researches on different kinds of renewable energies including photovoltaic technology are developing rapidly. It is proved that the output power of a PV cell is reduced by increasing the temperature. In this paper, mounting aluminum fins at the back surface of the PV module is proposed as a simple and low-cost method to decrease the PV cell temperature. It was found that using aluminum fins caused more than 7°C reduction in the cell temperature. Besides, it was shown that the entropy generation of the PV module with fin, was 3.5% lower than the conventional one. Also, the positive environmental impacts of using fins at the back surface of the PV module were estimated by RETScreen software, so that, it leads to enhance the performance of the PV power plant by more than 25 %, from an environmental viewpoint. [ABSTRACT FROM AUTHOR]