A vacuumed tube solar water heater, integrated with nanofluids has been investigated, experimentally. Since the water based nanofluids were tested a lot, here, the oil based nanofluids are considered. Three working fluids of pure oil, Al₂O₃/oil and TiO₂/oil are examined as a medium fluid with constant concentration of 1 wt.%. The mentioned nanofluids were flowing through a U-tube path, embedded in the vacuumed tubes. As assessments, both first and second laws of thermodynamics were considered. Finally, the water reached the temperatures of 68.1˚C, 60.2˚C and 45.4˚C, for working fluids of Al₂O₃/oil, TiO₂/oil and pure oil, respectively. So, Al₂O₃/oil showed 9% and 31% higher thermal efficiency than TiO₂/oil and pure oil, respectively. Also, from second laws of thermodynamics, a modified approach has been used to calculate the exergy efficiency. Then, the results were compared with the common exergy efficiency formula and up to 6.1% difference was seen between them. Finally, the entropy generation is also evaluated in this paper.

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.