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Leveraging the Experimental Method to Inform Solar Cell Design. Mary Annette Rose Jason Ribblet Heather Hershberger International Technology Education Association February 22, 2008, 2:00-2:50, Room 251E. M.A. Rose, 2008. Science-Technology Enterprise. Symbiotic Relationship.
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Leveraging the Experimental Method to Inform Solar Cell Design Mary Annette Rose Jason Ribblet Heather Hershberger International Technology Education Association February 22, 2008, 2:00-2:50, Room 251E M.A. Rose, 2008
Science-Technology Enterprise Symbiotic Relationship Mutual Dependence Images: The School of Science and Engineering, The University of Waikato. Retrieved http://sci.waikato.ac.nz/about_the_school.shtml
Thin-Film Solar Cells Collaboration of the National Renewable Energy Laboratory & Heliovolt to develop a solar cell using a copper-indium-gallium selenide (CIGS) semiconductor. Scientific challenge: to understand the chemistry and microscopic structure of the material in order to optimize its electrical properties. Engineering challenge: develop a reliable manufacturing process—akin to a printing process— that produces standard size modules (15 & 30-cm wide). Bullis, K., (2007). Making cheaper solar cells. Technology Review. Wednesday, September 12, 2007. Retrieved January 23, 2008, from http://www.technologyreview.com/Energy/19369/page1/
Challenge for Technology Education Science Content & Process Technology Content & Process
Presentation Goal Photochemistry Solar Cells Inquiry: Experimentation Design
Observing Phenomena Stimulate intellectual curiosity • What is happening in this system? • What energy is at work here? • What are the inputs, processes, and outputs of the system? • What happens if we block the cell from the sun? • What happens when we reverse the probes of the multimeter on the plates of the cell?
Parts & Materials List Component Function Parts Material Qty - Size Case Water–tight transparent housing Front/Back 1/8” Acrylic 2 pcs of 4 1/8”” x 4 1/8” Sides/Bottom 1/8” Acrylic 1 pc of ½” x 12” Plates Anode and Cathode Cuprous Oxide Cupric Oxide 0.20” Copper, Unpolished 2 pcs of 3 7/8” x 5” Salt Solution Medium of ion exchange Salt (NaCl reagent grade) 15% NaCL or 17.6 g Distilled Water 85% H2O or 100 ml Solar Cell: Photoelectric Effect
Challenge Students to… • Take on the role of a photochemist • Learn how solar cells convert light into electricity • Inform cell design
Photochemistry is… • study of chemical reactions of molecules in excited states produced by the absorption of light energy, i.e., photon • infrared (700–1000 nm) • visible (400–700 nm) • ultraviolet (200–400 nm) • electron transfer and ionization
Challenge Students to… • Take on the role of a photochemist • Learn how solar cells convert light into electricity • Inform cell design • Plan, implement, and interpret an experiment
Experiment: Method for Investigating Variables To what extent does the distance from the light source effect the power production of solar cells? Cause Effect Independent Variable Dependent Variable Outcome Variable Treatment Variable
What variables influence the power output of the cell? List Variables & Identify Elements • Concentration of salt solution • Distance between plates (E) • Surface area of plate (Cu2O and CuO) • Type of light (frequency) • Intensity of the light • Thickness of copper plate
Form Teams and Assign to Treatment Conditions Sam Bob Inga Fran Ted Harry Treatment Group 1 5% Solution 2 1 Ted Laura Elsa Howard Sally Frank Treatment Group 2 15% Solution 3 4 Bill Jean Remi Martha Rex Harris Treatment Group 3 25% Solution 6 5
Day 2 & 3: Manufacture Cells Specifications Top/Back: C x B Side: D x (2B+C) Plate: F x A A = 5” B = 4 1/8” C = 4 1/8” D = 1/2” E = 3/16” F = 3 7/8”
Homework: Literature Review Students discover more about… semi-conductive materials, the photoelectric effect, the interaction of energy and materials, and solar (photovoltaic) cells.
Chemical Safety For laboratory safety, see the National Institute for Occupational Safety (NIOSH, 2006).
Day 4: Procedure for Data Gathering Stimulate planning • What procedure will we use to test the cells? • How can we assure systematic and consistent testing conditions? • Why does a scientist strive for consistent experimental conditions? Set-UP Measuring Recording
Interpreting the Results • Level of salt in the solution impacts performance with best performance occurring at 15% • Tilt impacts performance with 90° tilt (perpendicular) consistently position resulting in best performance • The best performing combination of factors was a 15% solution at 90° tilt
The Photoelectric Effect h= Planck’s Constant v = frequency 1 eV = 1.6 x 10-19 joules Yaqoob, T. (n.d.). Photoelectric effect [Image]. John Hopkins University. Retrieved from http://www.pha.jhu.edu/~yaqoob/8m/lecture2/photoelectric_1.gif
What is happening in the solar cell? • Excitation of a Cu2O: • Negatively charged ions move through circuit, • Positively charged ions break free, and • Combine on the raw copper plate.
Solid State PV Cell Michell, R. (2000). A Seimens crystalline PV cell. WisconSUN. Retrieved from http://www.wisconsun.org/learn/learn_intro.shtml; Renewable Energy Works. (n.d.) Photovoltaics.[Image]. Retrieved 3/10/06, from http://www.renewableenergyworks.com/pv/PVDefn/PVDefn.html
Characteristics of Experimental Designs • Pose a research question which identifies the treatment (IV) and an outcome (DV) variable. • Select & assign a sample to treatment conditions • Experimental group (Receives treatment) • Control group (No treatment) • Comparison groups (Different Levels of treatment) • Apply treatment to one or more groups • Control extraneous variables • Measure outcomes • Statistically describe and represent the data • Statistically test the hypothesis
Inquiry is a Search for Understanding • Spurred by intellectual curiosity • Process is characterized by … • observing phenomena • asking questions and hypothesizing • systematically gathering and analyzing data • theorizing about the meaning of the evidence • Enabled by objective, measurable, and replicable methods
Best Practices & Scaffolding • Initiate intellectual curiosity • Ask questions, and encourage students to form questions • Provide increasingly more complex models (conceptual-to-realistic) of the photoelectric effect • Provide visual examples and simulations of photochemical processes • Provide access to diverse resources, e.g., chemistry and physics • Guide students through experimentation: sampling, hypothesizing, identifying variables, planning procedures, analyzing data, interpreting data • Require sense-making activities, such as collaborative discussion and the creation of cause and effect diagrams • Require students to apply experimental findings to the re-design of a solar cell.
Contact …. Mary Annette Rose Ball State University arose@bsu.edu 765-285-5648 http://arose.iweb.bsu.edu
Leveraging the Experimental Method to Inform Solar Cell Design Mary Annette Rose Jason Ribblet Heather Hershberger International Technology Education Association February 22, 2008, 2:00-2:50, Room 251E M.A. Rose, 2008