Two Page Research Paper (Solar Energy)

Solar Energy – How Does It Work?


By: Jenzel Espares, 9th Grade


Solar energy is a real mystery to many people, and although they are surrounded by objects that use solar energy such as a calculator, a traffic light, and sometimes, you might even find solar panels on the roof of someone’s home? What does solar energy do? Well, solar panels are used to take in the sunlight that we get during the day and are used to help create an electrical current. This then powers up objects, ranging from a small calculator to an entire house. Right now, people are working towards switching to renewable energy, such as solar energy, in order to fight against using emissions and speeding up global warming. Although we haven’t reached that point yet, many people are working towards a dream when one day, we can rely on the sun to be used as free electricity. When there is a sunny day, the sun shines almost 1000 watts of power per square meter on the entire planet. So, if we can get all that energy, we can power up the entire planet for no cost at all! Although solar energy is a great alternative to fuel, the question that is being looked into is basically…how does solar energy work?


Inside a solar panel are photovoltaic cells (photo = light, voltaic = electricity, photovoltaic = electricity from light), which are made from a semiconductor type of material called silicon (Si). A semiconductor is something that has an N-type and a P-type of its element in it. That will be explained later. Anyways, an atom of silicon is made up entirely of 14 electrons, meaning that its first and second shells are completely filled with 7 electrons each. The outer, or valence, shell only is half full with a total of 4 electrons, and it needs to find 4 more electrons in order to be satisfied and have its electrons be completely neutral. When sunlight strikes on the solar panel, some of that energy goes inside the silicon and it knocks some electrons off its bonds, making them move around freely (those electrons are called free carriers). Photovoltaic cells also have either one or more magnetic fields that force the electrons that broke free when sunlight struck the cell to move in one direction. This flow of electrons in one direction is called a “current”. Once wired up to a load (the object that needs to be powered up), the current made by those electrons pass through the wire and power up the object.


So, in the solar panel, in order to make the solar panel help power up the silicon is made with impurities, meaning that in that silicon, there are also some other atoms, including boron and phosphorous. Silicon atoms mixed with phosphorous actually take less energy for their electrons to break loose from them because some of the extra phosphorous atoms are not in a bond, and the other atoms beside it aren’t holding it together. So, more than normal electrons break free in that silicon, the silicon becomes N-type, meaning that it is negative. If we used pure silicon instead of doping (adding impurities to an atom), it wouldn’t work as well because supposedly N-type silicon is a much better kind of conductor than normal silicon would.


As said earlier, there is also a P-type silicon inside the solar cell. This part of the silicon is doped with boron, an element that only has 3 electrons in its outer shell rather than 4. The absence of electrons makes this P-type, meaning that it is positive. Since there are less electrons in this type of silicon, there are more holes, places where there are no electrons, and they move exactly the same way electrons do. So, when the N-type silicon and P-type silicon are placed next to each other, the extra electrons in the N-type rush over to the P-type silicon where there are free holes waiting for electrons to fill it. This means that there is a stampede of electrons from the N-type silicon to the P-type silicon, trying to get a space to fill in the holes.


Anyways, do you remember that every photovoltaic cell has at least one electric field? That electric field is essential in the solar cell for it to work. Anyways, when the electrons fill in the holes, the P-type becomes neutral, but now the N-type silicon becomes positive because there are no more electrons there. So, the electrons try to go back to the N-type where there are holes, but there is an electric field that was made by the electrons when they crossed to the P-type silicon. This ends up making them not be able to go back that way, and now they are stuck on the P-type silicon, cramped together with other free carriers. Well, if an external path was made, for example by wires, then the electrons can use that to get back to the N-type silicon. Of course the wires are connected to the load, and as the electrons pass through it, it powers up the load with electricity. Once it gets back to the N-type silicon, the P-type is once again unbalanced, and so they cross to the other silicon and then go back through the wire to the N-type silicon. This continuous motion creates a current of electricity, powering up the load with the necessary electricity that it needs to work. That is basically how a solar cell in solar panels works to create electricity.


Drawbacks:
  • Battery is needed in order to store the electricity gained from the sun
  • Many oil companies that rely on fuel oppose this idea
  • Getting solar panels are very expensive at the moment
  • Solar energy can only be obtained during the day, except if there are clouds covering the sun

Parts of a Solar Panel

solar3.gif

A. Cover Glass
B. Anti-Reflective Coating
C. Contact Grid
D. N-Type Silicon
E. P-Type Silicon
F. Back Contact

By using solar energy, I just might be able to power up a hot plate so that it can end up boiling a cup of water. According to Ms. Thomas, if I get my own small solar panel, I can scratch off the back and the cover glass of the solar panel so that I can get to the N-type and P-type silicon. Then I can hook up wires to each side and use that to power my hot plate. My alternative is to make my own solar panel using household objects, and then hook it up to the hot plate and see whether it works. Overall, solar energy is a very good idea, not only for my object, but as an alternative for all objects that require fuel. There are only a couple of drawbacks that make this renewable energy be less popular than it should be.

Reference: http://science.howstuffworks.com/solar-cell.htm and Ms. Thomas

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