08-01-2013, 12:58 PM
STUDY OF EFFECT OF DIFFERENT WAVELENGTHS ON PHOTOVOLTAIC CELLS
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Abstract:
Photovoltaic cells provide an additional method of acquiring energy, converting sunlight directly into electricity through the use of semiconductors. Effective photovoltaic implementation is reviewed, focusing on semiconductor properties and overall photovoltaic system configuration.
This experiment is designed to look at the effect of wavelength (color) of light on the output of a solar cell. This experiment performed shows the effect of different color on the photovoltaic cell. The photovoltaic cells give high efficiency under sunlight. However, with the help of this experiment it is tried to decipher whether using different colors the efficiency is improved or not.
This experiment shows a range of 4 colors: Blue, Green, Yellow and Red. Red is known to have the maximum wavelength. While blue has the minimum wavelength. The following experiment determines the efficiency and fill factor for the given colors. Thereby, observing the effect of different wavelengths (colors) on the photovoltaic cell.
Introduction:
Wavelengths:
Solar cells generate an electrical current when light hits their surface. White light that we see from the Sun includes all colors of the visible spectrum and ranges in wavelength from about 400 nanometers (nm) to about 780 nm. Solar cells vary in their response to different wavelengths, or color, of light
Theory:
Photovoltaic cell
Photovoltaic cells offer consumers the ability to generate electricity in a clean, quiet and reliable way. Photovoltaic systems are comprised of photovoltaic cells, devices that convert light energy directly into electricity. Because the source of light is usually the sun, they are often called solar cells. The word photovoltaic comes from “photo,” meaning light, and “voltaic,” which refers to producing electricity. Therefore, the photovoltaic process is “producing electricity directly from sunlight.” When applications require larger amounts of electricity and are located away from existing power lines, photovoltaic systems can in many cases offer the least expensive, most viable option. Solar photovoltaic cells are silicon-based units that use the photoelectric effect to convert light from the sun into energy. Solar panels consist of many cells and serve as energy alternatives for modern industry.
Photovoltaic effect
The photovoltaic effect is the creation of voltage or electric current in a material upon exposure to light. In the photoelectric effect, electrons are ejected from a material's surface upon exposure to radiation.
The collection of light-generated carriers does not by itself give rise to power generation. In order to generate power, a voltage must be generated as well as a current. Voltage is generated in a solar cell by a process known as the "photovoltaic effect". The collection of light-generated carriers by the p-n junction causes a movement of electrons to the n-type side and holes to the p-type side of the junction. Under short circuit conditions, there is no build up of charge, as the carriers exit the device as light-generated current.
FORMULAS USED
Fill factor
The short-circuit current and the open-circuit voltage are the maximum current and voltage respectively from a solar cell. However, at both of these operating points, the power from the solar cell is zero. The "fill factor", more commonly known by its abbreviation "FF", is a parameter which, in conjunction with Voc and Isc, determines the maximum power from a solar cell. The FF is defined as the ratio of the maximum power from the solar cell to the product of Voc and Isc. Graphically, the FF is a measure of the "squareness" of the solar cell and is also the area of the largest rectangle which will fit in the IV curve. The FF is illustrated below.
Conclusion
It is observed that the fill factor under tube light is greater than that under sunlight. Furthermore it is noted that the fill factor increases as color changes from higher frequency to lower frequency.
In Physics, using the visible spectrum, you will find that the higher the frequency of the light, the more energy it carries, from the equation-:
Energy = Planck's constant * Frequency
i.e. so in reality blue light carries more energy than red light.
The output power of a solar panel will change with the color (wavelength) of incoming light.
The efficiency increases as the frequency of color decreases. It is also concluded that solar cell acts more efficiently in sunlight to that of tube light.