<Reflections>
My original plan at first was to compare spherical, plane and parabolic reflectors but I had difficulties getting plane and spherical reflectors for my experiment so I had to modify my plans. However, by comparing parabolic reflectors with different curvature, I also got to find out how specific elements greatly affect the light absorbance of solar cells and was easy to implement other elements into the experiment as well. Moreover, I wasn’t sure how I could set up the experiment to test the effect of Fresnel lenses but eventually, I decided to use two parabolic reflectors for the light rays to pass through the lenses. Overall, this project not only allowed me to gain deeper knowledge in maximizing efficiency of solar energy but also trace future development of solar energy.
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<Future Solar Energy Appliances>
In future, to further enhance the efficiency of solar energy, nanoscaled solar materials can be used. The nanoscaled solar materials offers a solution in increasing panel’s efficiency by allowing the light to flow through the surface and stored into the material. There are many ways these nano scaled metamaterial can be applied in our real lives in the future. With further research, these metamaterials can be used to create appliances such as “super solar panels”. Although, it was once only a theoretical structure that could capture images below the diffraction limit through the use of the negative refractive index, scientists are now one step closer in producing it. We can also apply this technique to produce a fancier design of super mini solar cells. `With these appliances, it is possible to store the light energy into the solar cell and use it efficiently and convieniently like a battery whenever we want. However this is only possible in specific type of materials, thickness, number of layers and incidence angle that the light comes through so there are still much progress to be made. The below diagram shows the structure of a hyperbolic meta material, which is formed of alternating layers of metal and dielectric. When the light goes through at particular angle, with particular type of material used to make the meta material, light can be stored in it. (light flows through) I measured the voltage of the solar cell between the fresnel lens 30 seconds after I shined the light and the results showed that the solar cell produced highest voltage when the distance between Fresnel lens and the 2nd parabolic reflector was greater. With the presence of Fresnel lens, the light rays were able to concentrate into the solar cell, demonstrating higher efficiency. The voltage produced increased as the distance between reflector and the lens increased. The rapid increase in the trend of the graph show great impact of Fresnel lens in voltage production of solar cells.
I also set up double parabolic reflectors with Fresnel lens in between to test out the effect of Fresnel lens in solar cell’s efficiency. I shined the flashlight so that the light rays would be reflected off the two parabolic reflectors and then go through the Fresnel lens. Fresnel lens is a type of lens effective in converging light rays as it consists of a series of concentric grooves etched into the plastic. They allow excellent light gathering ability as these contours act as individual refracting surfaces, bending parallel light rays to a common focal length as shown from the diagram. I manipulated the location of Fresnel lens in between the two parabolic reflectors and also measured the voltage produced by the solar cell when without the Fresnel lens.
Diagram #1 shows the set up of my experiment and diagram #2 shows the structure of the fresnel lens that allows the light rays to converge. After the reflector shape experiment, the results were as following:
1) Surface Temperature (F) 2) Focus Temperature (F) Reflector A, which was neither wide nor narrow, had the most temperature change out of the three reflectors due to its ability to concentrate the light rays into the solar cell. If the reflector was too narrow, there wasn't much area for the light rays that were reflected to converge. When the reflector was too wide, most of the light rays just diverged and weren't able to be absorbed in to the solar cell with greater intensity. I tested out various reflector shapes - narrow parabolic reflectors and wide parabolic reflectors - to see which one was the most efficient. I measured the temperature change of the focus and the surface to measure the efficiency. The greater the temperature change, it indicates that the heat was more concentrated and absorbed. I tested out three models of parabolic reflectors and their curvature is shown below. I predict that reflector 2 would have the highest temperature increase since it is not too wide or narrow so it can converge light rays into one point more efficiently.
1. y = 1/ 12.25 x^2 2. y= 1/25 x^2 3. y = 1/64 x^2 < Plan for my reflector experiment >
Looking around the internet, there weren’t any parabolic or spherical reflectors that was for experimental usage. Most of them were generally enormous, usually for setting it up on the rooftop for collecting sunlight. I could only find plane reflectors and solar dishes. So I plan to set up a experiment using the plane reflectors like the sketch below, to see the effect of plane reflectors. I am going to compare when solar panel without reflectors and with reflectors to see how big of a difference it makes and to understand more about the reflector’s role in concentrating the light on to the collector. < Research on solar energy reflectors >
Solar concentrator (solar dish) = example of parabolic reflector A parabolic solar concentrator tracks the sun throughout the day using dual axis tracker. Sun’s solar energy shines onto the collector, which has highly reflective surface and reflects concentrated solar power on to a receiver at magnification of 1000X. The solar concentrator focuses the light to the CPV Dense Array Molecule, which consists of multijunction solar cells. These converts concentrated solar power to electricity. The high amount of electricity is generated by the highly reflective and concentrative parabolic reflector with high efficiency. I got started on my incidence angle and intensity of sunlight experiment using light stand, voltmeter, cloth and protractor. For the angle experiment, I set the light stand to be 0, 15, 30, 45, 60, 75, 90 degrees angle to the solar panel. I kept the distance between the light source and the panel as 40cm constantly for accurate results.
I interviewed Mr Evans,who was my STEM mentor last year for research on renewable energy, for my signature project. Mr Evans is 66 years old and is currently a physics and chemistry teacher in Emma Willard School. He was born in New York and majored in astronomy and physics in college. He taught physics in two different schools in Vermont before he came to Emma Willard.
He definitely thinks that the rapidly developing renewable energy is a good replacement for fossil fuels. "With the temperature of earth increasing, the more we can switch into types of energy source that does not produce green house gas, the better for the environment and society." He also thinks that the main drawback of solar energy is its dependence on location, weather patterns and seasonal angles of the sunlight. Solar energy would be difficult to harness in location where they doesn’t get much sunlight, or especially during winter. The obvious advantages of solar energy for him is that there is no pollution or emission of green house gas as well as being renewable and sustainable. He thinks that the main environmental problem the earth would face 100years from now on would probably be climate change. There would be a lot of areas underwater, resulting in large migration of people to other locations. Mass movement of people would also lead to stress on new locations with overflowing people. They would all need housing, food and too many people in certain locations would definitely give a rise to new environmental problems. This was a chance for me to think more about the current and future environmental problems of earth and the resolution solar energy could offer. |
Irene Jeong's signature project:Conducting various experiments using school's solar panel to find out the optimum environment for maximum efficiency of photovoltaic cells Archives
May 2017
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