Solar cells Essay Example for Free

Solar cells Essay I am trying to find out how the current changes with the area of the solar cells. THEORY The energy in light can be transformed into electricity when shone onto semiconductor materials. Silicon and germanium normally have electrons in low energy states. Absorption of light excites these electrons into higher states and generates a voltage (typically 0. 5 V per cell). As more light is absorbed, more electrons are excited and the current supplied increases. The energy of the photons transfer to electrons in the semiconductor. The energized electrons then break free for the silicon atoms and transfer them to an electric circuit. If we completely cover the top of a solar panel then, then photons cannot get through the conductor, and the current is lost. Internal Resistance (called series resistance) if this is high then this means high losses, to minimize the losses; the cell is covered by a metallic contact grid that shortens the distance that electrons have to travel. FAIR TESTING In this experiment I will only change 1 factor, which is the area of solar cell. I would have to change the card placements which I will use to cover the solar cell at the same measurements every time. I will change the length of the card each time from 100%, 75%, 50% and 25%. The following factors that are going to be kept constant are:- 1. The distance from the lamp to the solar cell if this is changed it will affect the number of photons hitting the solar cell for each reading. 2. The positioning of the lamp if this is changed; it could also affect the number of photons hitting the solar cell for each reading. The lamps must point at the solar panel only. 3. The time this, would have to be accurate i. e. not leave the solar panel under the lamp for too long or it could affect the temperature and the intensity of the light producing photons on the solar cell. The light source The intensity of the light source will be kept the same to prevent more or less photons hitting the solar cell for each reading. 5. The bulb watt this would have to be kept constant, i. e. if I use double the watt of the bulb that double the photons will hit the solar cell. 6. The card If this is change, than this could affect the number if photons which hit the solar cell. PREDICTION Using my scientific knowledge and preliminary research I predict as the percentage area uncovered increases; more photons will hit the semi conduct device, meaning more electrons will be released resulting in more electric current.