Solar Energy Literature Review

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Chapter two Literature review 2.1 Introduction Energy is the primary and universal measure of all kinds of work by human beings and nature. Primarily, it is the gift of the nature to the humankind in various forms. The consumption of the energy is directly proportional to the progress of the humankind. With ever-growing population, improvement in the living standard of the humanity, industrialization of the developing countries, the global demand for energy increases day by day. The primary source of energy is fossil fuel, however the finiteness of fossil fuel resources and large scale environmental degradation caused by their widespread use, particularly global warming, urban air pollution and acid rain, strongly suggests that harnessing…show more content…
They are called solar after the sun because the sun is the most powerful source of the light available for use. Solar cells or PV cells rely on the photovoltaic effect to absorb the energy of the sun and cause current to flow between two oppositely charge layers. A solar panel is a collection of solar cells. Although each solar cell provides a relatively small amount of power, many solar spread over large area can provide enough power to be useful. To get the most power, solar panels have to be pointed directly at the Sun. Solar panels are formed out of solar cells that are connected in parallel or series. When connected in series, there is an increase in the overall voltage, connected in parallel increases the overall current. Each individual solar cell is typically made out of crystalline silicon, although other types such as ribbon and thin-film silicone are gaining popularity. PV cells consist of layered silicon that is doped with different elements to form a p-n junction. The p-type side will contain extra holes or positive charges. The n-type side will contain extra electrons or negative charges. The difference of charge forms a region that is charge neutral and acts as a sort of barrier. When the p-n junction is exposed to light, photons with the correct frequency will form an extra electron/hole pair. However, since the p-n junction creates a potential difference, the electrons cannot jump to the other side…show more content…
3.4.1 Light Dependent Resistor Light Dependent Resistor is made of a high resistance semiconductor. It can also be referred to as photoconductor. If light falling on the device is of the high enough frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electron conducts electricity, thereby lowering resistance. Hence, Light Dependent Resistors is very useful in light sensor circuit. LDR is very high resistance, sometimes as high as 10MΩ, when they are are illuminated with light resistance drops dramatically. A Light Dependent Resistor is a resistor that changes in value according to the light falling on it. Connecting the LDR to the microcontroller is very straight forward, but some software “calibrating” is required. It should be remembered that the LDR response is not linear, and so the readings will not change inexactly the same way as with a potentiometer. In general, there is a larger resistance change at brighter light levels. This can be compensated for in the software by using a smaller range at darker light levels. Figure 3.3 show Light Dependent

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