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Understanding Solar Energy Fundamentals and System Design Considerations

This lesson explores solar energy fundamentals and system design factors through outdoor learning. Key topics include peak sun hours, fill factor, and the incident radiation equation. Students will resume NEC calculations, engage in individual project discussions, and preview Homework #2, which focuses on solar energy applications outside the classroom. Resources available include magazines, support societies like ASES and NESEA, and a comprehensive solar library. The session incorporates technical calculations, efficiency discussions, and measurement techniques for solar radiation.

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Understanding Solar Energy Fundamentals and System Design Considerations

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  1. Lesson 3 22.525 Sep 18, 2014

  2. Agenda Return HW#1 Learning about solar outside the classroom Peak sun hours, fill factor, incident radiation equation Resume work on NEC calculations BREAK Lecture: system design factors Individual project topics Lecture: Fundamentals of Converting Sunlight into Electricity HW#2 preview

  3. Solar Outside the Classroom • UML Solar Club • Joining ASES/NESEA and other societies • Subscriptions to solar and related magazines • Solar “library” in Kitson210 • Websites • dsireusa.org • NREL.gov • solarabcs.org • solrenview.com • solarbuzz.com • solarindustrymag.com • masscec.com • eia.gov • energy.gov • seia.org

  4. Some More Background Info 22.525

  5. Peak Sun HoursUnderstanding “Solar Resource” • Peak sun hours for a location is numerically identical to the average daily solar insolation • Data can be used to compare relative solar resource availability between two locations 1 kW/m2 solar radiation Time of day Time of day

  6. Maximum Power PointCell/Module I • Power = Voltage X Current • I-V Response curve • Pmax occurs at max voltage and current • Vmpp and Impp on data sheets • Pmpp varies based on solar insolation and resistive load connected to module Isc Impp V Vmpp Voc

  7. Fill Factorthe “quality” of a solar cell Isc Impp V Vmpp Voc

  8. Efficiency of a Solar Cell E = solar insolation in w/m2 A = area of cell in m2 This is theoretical efficiency. For Si-based cell, upper limit is 28.6%. Other losses (recombination, shading from contact “fingers”, etc.) lower efficiency below what is calculated above.

  9. Total Hourly Solar Radiation on a Horizontal Surface, Ih To the board again…

  10. TMY3 Revisited measured with pyranometer measured with RSR2 or similar device RSR = Rotating Shadow band Radiometer

  11. To the board, nochein mal!

  12. Total Hourly Radiation on Surface of Tilted Collector IC = solar radiation incident to a tilted collector Ibc = beam component of radiation incident to tilted collector Idc = diffuse component of radiation incident to tilted collector Irc = reflected component of radiation incident to tilted collector How do we calculate these? Back to the board…

  13. Total Hourly Radiation on Surface of Tilted Collector

  14. Back to NEC • Clarification on temperatures • 25 degrees C at STC DOES refer to cell temperature • However, I would suspect that under test conditions, cell and ambient temp would be the same • When checking max voltage, you CAN use the method we used last week • Looking for worst case, which means cell temp = cold ambient temperature • Hence, Okay to use ASHRAE ambient temp with temp coefficient from module manufacturer

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