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Lesson 3

Lesson 3. 22.525 Sep 18, 2014. 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 I ndividual project topics

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Lesson 3

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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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