Solar Cells Steven Thedford Redan High School Objective cell. Student will be able to determine the maximum powerpoint and efficiency of a solar Background Information Solar cells, photovoltaic cells, convert sunlight into electricity. Many solar cells consist of three layers: a glass protective layer, the electron abundant material ( n-type layer), and the electron deficient material (p-type layer). The uppermost layers consist of glass, the middle is a semiconductor such as silicon along with impurities and the bottom layer and the bottom is layer is p-type. Therefore, when a photon of sufficient frequency strikes an electron in the p-layer, an electron is released into the n-type electron causing an excess of electrons. That current can be discharged into a wire and stored as energy. Solar cells produce electricity when light hits their surface because of the photoelectric effect. In the photoelectric effect photons transfers energy to an electron upon bombardment. In other words, the photon or light wave collides with an electron from an atom and transfers some of its energy to it. The photon's energy (E photon ) is Planck's constant (h, or 6.36 * 10-34 J/s) multiplied by the frequency of the light (f). The frequency is equivalent to the speed of light (c), divided by the wavelength ( ). The energy of the a photon is given by the equation E photon = hf, f = c/ E photon is the energy of the photon, h is Planck s constant (6.36 x 10-34 J/s) and f is the frequency. In addition, c is the speed of light ( 3 x 10 8 ) and is the wavelength in meters. Materials: 1. 0.5 V Solar Cells (3) 2. Multi-meter 3. Voltage Supply 4. Wire 5. Light Emitting Diode (LED )
Procedures 1. Connect the LED, ammeter, voltage supply and solar cell as illustrated in the circuit diagram illustrated in the appendix 2. Apply different several different voltages to the cell 3. Read the current reading on the ammeter. 4. Record your data in Table I. 4. Repeat the procedures for a different voltage. Maximum Power Point Solar cells can operate in a large ranges of currents (I) and voltages(v). The voltage of a solar cell does not depend on the size of the cell and for the most part remains constant with changing light intensity. Yet, the current in a cell is directly proportional and light intensity. Also, there exist a current and voltage, less the maximum current or voltage, that produces a maximum power output. This condition is called the Maximum Power Point (P m ) and can be calculated by multiply the voltage and current to get the largest result that is possible, given by the equation: P m = I x V where P m is the maximum power point, I is the current, and V is the voltage of the solar cell. Energy Conversion Efficiency The energy conversion efficiency (, "eta") of a solar cell is the percent of power converted from absorbed light to electrical energy and collected; when a solar cell is connect to an electrical circuit. The equation is given by, where P m is the maximum power point; E is the input light irradiance, and A c is the surface area of the solar cell. The unit of irradiance (E) is W/m 2 and the area is also in m 2. Moreover, the standard solar readiaton has a power density of 100 wats per square meter.
Analysis 1. Using data from table I, graph the current (I) vs Voltage (v) 2. Calculate the maximum-power point for each color using the equation P m = I x V where P m is the maximum power point, I is the current, and V is the voltage of the solar cell. 3. Calculate the efficiency of the solar cell using the equation for each color filter Questions 1. What was the maximum power point of your solar cell? 2. What does the maximum power point tell you about your solar cell? 3. What was the efficiency of your solar cell? 4. What does your data tells you about your solar cell? 5. How does your data compare to the efficiency of a solar cell in industry?
Discussion: Video Story In this activity you will create a video story. Thus, you will have to create a script of the events that took place during your laboratory. First, use a story board to the create scenes. Storyboards can be found in the appendix, which is located in the last pages of these of this laboratory. Afterwards, practice the scenes with your group members and when you think your members are ready use a digital video recorder to film your movie. Import the movie file into in a movie software program (imovie, movie maker) to view your finished product. Reading & Writing In this exercise your teacher will provide you with an article about other solar energy. As you read the article, underline, five important facts that were present in the article. Write a summary that expresses your how you think about the article. Afterwards, write your local state representative and asked them to support a bill that would support the use of alternative energy, such as solar energy. Your teacher will provide you with the name and address of your representatives. Technology ( Georgia Public Broadcasting Classroom Physics 1302) View the GPB Public Broadcast Classroom Physics 1302 video on the wave and particle properties by surfing to the website: http://www.gpb.org/public/education/classroom/physics/index.jsp?pcode=ep1302. The videos discusses the wave and particle properties of light, as well as the methods for the production of light. Take notes during the video. Afterwards, take the particle of light quiz on the Physics Place.
Appendix
Color and Wavelength of Light Table I Trails I(mA) V (Volts) 1 2 3 4 5 6 7
Circuit Diagram Solar Cell + - Ammeter A - + LED - Voltage Supply
Laboratory Storyboard Group Number: Title: Date: Overview Motion pictures are made of thousands of scenes or frames that have been draw on a story board. You will use those same techniques to make a movie or your laboratory. Discuss with your groups members the laboratory that you conducted. Afterwards, create a story of the laboratory. The frame represents scenes of the story.that Draw a picture/diagram of the scene and write out the narration-the conversion that took place during the scenes. Remember, that a good movie needs a introduction, middle, and end. Frame # Diagram of Picture The Narration/ Soundtrack Score Level
Laboratory Storyboard Frame # Diagram of Picture The Narration/ Soundtrack Score Level
Laboratory Storyboard Frame # Diagram of Picture The Narration/ Soundtrack Score Level
Laboratory Storyboard Frame # Diagram of Picture The Narration/ Soundtrack Score Level
Laboratory Storyboard Rubric Points Knowledge Base Comments 20 The group demonstrates no or little knowledge of understanding of the photoelectric effect and its and solar cells 40 The groups demonstrates misconceptions of the photoelectric effects and solar cells. 60 The group demonstrates an accurate understanding of the photoelectric effect and solar cells. 80 The group demonstrates a complete and accurate understanding about the photoelectric effect and solar cells. Moreover, provides additional information on the concepts. 100 The groups demonstrates superior understanding of the photoelectric electric and solar cells. Furthermore, it provides new insights and suggest additional uses of solar cells.
National Educational Technology Standards for Students: The Next Generation What students should know and be able to do to learn effectively and live productively in an increasingly digital world 1. Creativity and Innovation Students demonstrate creative thinking, construct knowledge, and develop innovative products and processes using technology. Students: a. apply existing knowledge to generate new ideas, products, or processes. b. create original works as a means of personal or group expression. c.. use models and simulations to explore complex systems and issues. d. identify trends and forecast possibilities. 2. Communication and Collaboration Students use digital media and environments to communicate and work collaboratively, including at a distance, to support individual learning and contribute to the learning of others. Students: a. interact, collaborate, and publish with peers, experts or others employing a variety of digital environments and media. b. communicate information and ideas effectively to multiple audiences using a variety of media and formats. c. develop cultural understanding and global awareness by engaging with learners of other cultures. d. contribute to project teams to produce original works or solve problems. 3. Research and Information Fluency Students apply digital tools to gather, evaluate, and use information. Students: a. plan strategies to guide inquiry. b. locate, organize, analyze, evaluate, synthesize, and ethically use information from a variety of sources and media. c. evaluate and select information sources and digital tools based on the appropriateness to specific tasks. d. process data and report results. 4. Critical Thinking, Problem-Solving & Decision-Making Students use critical thinking skills to plan and conduct research, manage projects, solve problems and make informed decisions using appropriate digital tools and resources. Students: a. identify and define authentic problems and significant questions for investigation. b. plan and manage activities to develop a solution or complete a project. c. collect and analyze data to identify solutions and/or make informed decisions. d. use multiple processes and diverse perspectives to explore alternative solutions. 5. Digital Citizenship Students understand human, cultural, and societal issues related to technology and practice legal and ethical behavior. Students: a. advocate and practice safe, legal, and responsible use of information and technology. b. exhibit a positive attitude toward using technology that supports collaboration, learning, and productivity. c. demonstrate personal responsibility for lifelong learning. d. exhibit leadership for digital citizenship.
6. Technology Operations and Concepts Students demonstrate a sound understanding of technology concepts, systems and operations. Students: a. understand and use technology systems. b. select and use applications effectively and productively. c. troubleshoot systems and applications. d. transfer current knowledge to learning of new technologies.
Resources 1. Science Fair Projects: http://www.juliantrubin.com/fairprojects.html 2. National Educational Technology Standards for Students: http://cnets.iste.org 3. Science NetLinks: http://www.sciencenetlinks.com/ 4. Version: Thinkfinity: http://www.thinkfinity.org/home.aspx 5. Georgia Public Broadcasting Classroom: http://www.gpb.org/public/
References The Photoelectric Effect Retrieved July 5, 2007 from the word wide web http://www.princeton.edu/~ccaro/papers/photoelectric_effect.html Grian D. C, Physics Prentice Hall Upper Saddle River, New Jersey 07458 Digital Story Telling Retried July 9, 2007 http://www.umass.edu/wmwp/digitalstorytelling/storyboard.htm Solar Cells (Photovoltaics) & Panels retrieved July 10, 2007 from the world wide web.: http://www.juliantrubin.com/fairprojects/renewableenergy/solarcells.html Office of Technology for Education (OTE) Copyright: 2001,. Digital Story Telling Retrieved July 11, 2007. http://www.cmu.edu/teaching/howto/digital_storytelling/index.html Carnegie Mellon University, All Rights Reserved Greeen, A. M. Solar Cells, Operating Principles, Technology and System Applications Printing Hall, inc 1998 Englewood Cliff, N. J. Solar Cells Retrived from the world wide web July 12, 1966. http://en.wikipedia.org/wiki/solar_cell#solar_cell_efficiency_factors Solar Cells Retrieved from the world Wide Web July 12, 1966. http://www.solarbotics.net/starting/200202_solar_cells/200202_solar_cell_use.html