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To provide the progressive global demand for energy, the use of renewable energies is being rapidly developed. Since solar radiation is available in most parts of the earth, the photovoltaic (PV) power plant is one of the worthwhile solutions. As a deficiency, temperature rise in photovoltaic cells leads to a drop in their electrical output power. In this experimental study, the circulation of carbon black nanofluid was investigated as a coolant of PV modules. Both water and ethylene glycol (EG) were used as the base fluids. It is found that all modified cases generate more output power than the conventional one. For instance, water + carbon nanofluid yields 54% more output power compared with the conventional one. To make a real assessment of using nanofluid as a coolant, the electrical consumption by pump and fan must be counted. Therefore, in this study, the net output power is calculated. In the cases of EG and EG + carbon, the net output powers get lower than the conventional module. So, they are not justifiable. In this paper, a modified formula is proposed to calculate the exergy efficiency, in order to achieve more accurate results. Accordingly, from an exergy viewpoint, 16.3% and 4.5% in electrical and thermal exergy efficiencies are achieved, when water + carbon nanofluid was used. Moreover, the values of entropy generation and lost exergy were reported for all considered cases. [ABSTRACT FROM AUTHOR]

The decrease in output power of a photovoltaic (PV) power plant with increase in temperature is one of the main issues which can be controlled by cooling the PV modules. In this experimental study, various numbers of 10, 20, 30 and 40 aluminum fins in two different geometries of straight and zigzag were mounted at the back side of PV modules. In order to conform the ambient conditions, experiments were done by a solar simulator, under constant irradiation of 630 W m−2. The main objective of the study is to measure the effect of mounted fins at the back surface of PV panels, on electricity generation by lowering the panel surface temperature. PV panels with zigzag fin geometry are found to perform better than those with straight fins and also the module without fins. The results show that in case of 10 fins, temperature drops of 9 °C and 15 °C and increase in output power of 8% and 14% are achieved for straight and zigzag geometries, respectively. The entropy generation as an important thermodynamic parameter is also evaluated and a reduction of 1.5% to 2.5% is found in different experiments. Follow-up potential research areas are also identified. [ABSTRACT FROM AUTHOR]

Increasing the temperature of photovoltaic (PV) cells decreases their electricity generation. The use of phase change materials (PCMs) is one of the most common methods for controlling the rate of increasing the temperature of PV cells. This research focuses on thermodynamic analysis of PV/PCM systems with and without fins in maximum operating temperature of PV modules (85 °C). Polyethylene glycol 600 (PEG-600) and paraffin, with different melting points, have been studied experimentally as PCM in an indoor condition. Moreover, the effect of using fins was investigated. For this critical temperature, the results showed that using paraffin could be better for controlling the temperature of PV cells, due to its closer melting point with the module temperature. In the case of fins included, the temperature differences of 28.0 °C and 8.8 °C between the case of paraffin + fin and the case of PEG 600 + fin in comparison with the conventional PV module were measured, respectively. At this critical temperature condition, the output power of a PV module cannot exceed the half of its nominal power. The exergy efficiency of the paraffin + fin case was measured to 4.2% more than the conventional one. Also, entropy generation was calculated and reduction up to 5% was shown for paraffin + fin in comparison with the conventional one. Moreover, variations of the Rayleigh number for proposed cases are calculated too. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) technology plays an important role in the progressing trend of using renewable energies in the world. Yet the negative impact of a cell's temperature rise on its performance is a major weakness of this technology. In this paper, the effects of both air blowing and emitted radiation are investigated experimentally in the ranges of 0–7.7 km/h and 360–840 W/m2, respectively. In this regard, using Central Composite Design (CCD), the experiment was designed and performed to evaluate the response of a PV module to both of the variables. The results show that the PV module temperature drops from 61 °C to 40 °C when radiation intensity is 840 W/m2 and air velocity is 7.7 km/h. This temperature reduction causes a 2.5 % rise in electrical efficiency. Three equations were derived in order to correlate the outcome of temperature, electrical efficiency, and output power of a PV cell, with respect to irradiation intensity and air velocity. It is realized that in order to enhance the PV module output power, the effect of air current velocity is potentially more promising than the irradiance intensity. Also, the results proves that the impact of cooling the module on electrical efficiency strongly depends on the level of irradiation intensity. • The effect of irradiation and wind blowing on a PV module performance were studied. • Using CCD, three relations were obtained as functions of radiation and air velocity. • The proposed correlations differ up to 3.1 % with the results of the other scholars. • To enhance the output power, the wind velocity is more effective than the radiation. [ABSTRACT FROM AUTHOR]