Soiling

The rate of soiling of photovoltaic modules depends on environmental parameters such as aerosol concentration , humidity and wind speed. Previously we found low correlations between daily averages of these values and the daily soiling rate of a PV system. In this study we aimed to achieve stronger correlations by increasing the measurement frequency, with a simple device able to quantify soiling in outdoor conditions in real time. The so-called outdoor soiling microscope developed could measure the deposit and removal of individual dust particles larger than 10 lm 2 every few seconds, and could detect the onset and disappearance of condensation. In an initial trial the device revealed qualitative relations between the parameters not seen with 24-h data. However most linear correlation coefficients remained low, suggesting the need for a more sophisticated model of outdoor soiling.

Energy is the driving force in all the sectors as it acts like an index of standard of living or prosperity of the people of the country. However heavy dependence on fossil fuels leads to global warming, hence there is a need for the use of clean, sustainable, and eco friendly form of energy. Among the various types of non-conventional energy solar energy is the fundamental as it is abundant, pollution free and universally available.Even though the main input to the PV system is the solar radiation still there are other factors which affects the efficiency of the pv module. In this paper real time experiment has been conducted to analyze the effect of various factors like irradiance, temperature, and angle of tilt, soiling, shading on the power output of the pv module. Temperature is a negative factor which reduces the efficiency of the module and can be reduced by various cooling arrangements. Presence of dust particles and shading obstructs the incident solar radiations entering the panel and the effect is seen in the iv and pv curve .For better performance solar tracking at maximum power point is suggested to improve the power output of the pv module.

The future of wind energy conversion will focus on making it as efficient as possible so that it is able to offset the large capital investments made in wind turbines. Small wind turbines are gaining popularity due to their ability to meet community or domestic needs in isolated areas with relatively easier installation and lower cost than large wind turbines. This study looks at optimizing the design of airfoils for use in small horizontal axis wind turbines. The optimization is aimed at maximizing the lift coefficient (Cl ) while minimizing or fixing the drag coefficient (Cd). To satisfy these two objectives a multi – objective genetic algorithm is used. The airfoil is parameterized using a composite Bezier curve with two Bezier segments and 13 control points. Appropriate curvature conditions are implemented at the leading and trailing edges of the airfoil and geometric constraints are applied to maintain the maximum thickness between 10% to 18% of the chord for structural reasons. Genetic algorithm (GA), which is a stochastic population based search algorithm, was integrated with XFOIL, a popular open source flow solver. GA generates suitable airfoils using 13 control points and the resulting coordinates of the airfoil are passed to the XFOIL which determines the characteristics of the airfoil and assigns a fitness measure to the respective airfoil. This fitness measure is fed-back to GA in a cyclic process towards optimizing the design of the airfoil. One of the resulting optimized airfoils USPX1 is tested in a wind tunnel and also analyzed with the CFD software ANSYS CFX. The two-dimensional airfoil characteristics of the optimized airfoil for small wind turbines are compared against the popular SG6043 airfoil and discussed.

In the frame of the European project, entitled MULTI-ASSESS, specimens of structural metals, glass, stone and concrete materials were exposed to air pollution at a station, which was installed for this purpose on a building, located in the centre of Athens. The main purpose of this project was to determine the corrosion and soiling effects of air pollution on materials. A set of the specimens was exposed in a position that was sheltered from rain and partly from wind, and another set was exposed in unsheltered positions on the roof of the above said building. In addition, other specimens were exposed at different heights on the same building, in order to investigate for the first time the corrosion and soiling effects on various materials as a function of height. For the determination of these effects, chemical analysis of the specimens was performed and basic parameters as the weight change, the layer thickness and the optical properties were calculated. Finally, the results obtained are discussed and their plausible interpretation is attempted.