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Effect of the Wind Velocity on the Efficiency of Solar Cell
Abstract
Performance of a Solar cell not only depends on its basic characteristics but also depends on the ambient variables like radiation, temperature, humidity, dust, wind velocity, cloud cover, clearness index, etc. V-I Characteristics of a calculator solar cell have been estimated at different wind speeds using wind tunnel. Slight decrease in efficiency of solar cell with the increase of wind velocity is observed. The effect of this on the performance of a solar panel is discussed in the paper.
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With increase of ambient temperatue there is a deficiency in electrical energy that solar cells supply than their values under ideal conditions (25 °c - 1000 w/m2), this sitiuation be of a high affection especially in countries of a hot climate. In this work the cell temperature inside a solar panel is calculated depending on values of ambient temperature, solar radiation and multi other parameters related to climate and solar panel manufacturing. The ideal and actual energy that is supplied by a certain area of solar cells under ideal and actual conditions is measured to determine the defficiency between the two cases, then a new formula is applied to determine the exact substitutive area of solar cells that must be added to the initial area so as the energy supplied by the cells under actual conditions is the same as that under ideal conditions.A comparsion and evaluation of the results are made for multi inclinations according to the climatic data of Baghdad city. Constants are derived for Baghdad city which can be applied in designing PV systems to get values of actual energy supplied by solar cells at any temperature are exactly the same as that calculated under ideal conditions at Tc=25 °c.
In this study, it was investigated how changes in spectral solar radiation effects the output of photovoltaic modules. First, there was a precise examination of the seasonal changes in spectral solar radiation. Consequently, it was found that the ratio of spectral solar radiation available for solar cell utilization, to global solar radiation, changes from season to season. It varied, from 5% for polycrystalline silicon cells, to 14% for amorphous silicon cells, throughout one year. Obviously a cell made from amorphous silicon is more severely effected by seasonal variations.Next, the seasonal changes of photovoltaic module output were examined. The output was calculated by the conventional output evaluation method using irradiance and cell temperature. This calculated value and the subsequently measured value were accumulated and the two values compared. As a result, the accumulated output of photovoltaic modules was confirmed as changing seasonally in the same way as spectral solar radiation. The output ratio of polycrystalline silicon was found to change by 4%, while that of amorphous silicon varied by 20%. Hence the seasonal variations in spectral solar radiation should be taken into account for optimum photovoltaic power system design.
The resuls of model simulations and analyses of operating solar cell efficiencies are reported. Defined as the ratio (%) between the electrical output power of the device and the total incident radiant power, this efficiency is somewhat ambiguous as it ignores the effects of temperature, total irradiance, and the spectral distribution of the light source. Since the total intensity and spectral distribution of sunlight varies with atmospheric conditions such as cloudiness, total column ozone, turbidity, and precipitable water, the efficiency of a cell operating in a field installation may also be a function of the above factors. This paper examines variation of modeled and observed cell efficiencies with atmospheric variations. Variations in turbidity and water vapor content drive the SPCTRAL2 solar spectral radiation model of Bird and Riordan (1986). Model output, coupled with prescribed spectral response functions representing monocrystalline and amorphous solar cells, is used to model the efficiency of these cell types. The modeled efficiency rises with increasing humidity, especially for the simulated amorphous cell. Simulated efficiency decreases with increasing turbidity for both modeled cell types. The amount of increase or decrease dependents on the spectral response specified. The measured performance of different solar cells operating at the PVUSA site in Davis, California is also analyzed. The major factors found to cause variations in operational efficiency are ambient temperature and total irradiance intensity. The authors also observed increases of the apparent efficiency of amorphous cells with decreasing energy in the red portion of the solar spectrum which are consistent with model predictions.