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ECE 333 Green Electric Energy

ECE 333 Green Electric Energy. Lecture 14 Monthly Clear-Sky Insolation , PV Intro Professor Tim O’Connell Department of Electrical and Computer Engineering. Announcements. Exam 2 is next Thursday , 8:00AM – 9:20AM Change from the original syllabus

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ECE 333 Green Electric Energy

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  1. ECE 333 Green Electric Energy Lecture 14 Monthly Clear-Sky Insolation, PV Intro Professor Tim O’Connell Department of Electrical andComputer Engineering

  2. Announcements • Exam 2 is next Thursday, 8:00AM – 9:20AM • Change from the original syllabus • ECE 431 field trip next Thursday (March 20th) • We are working on a Conflict Exam for Wednesday, March 19th. • Start reading Chapter 5 • Today: Finishing Chapter 4, Starting Chapter 5

  3. Review: Solar Insolation on a Collecting Surface • Direct-beam radiation on the collector face is just a function of the angle between the sun and the collecting surface (i.e., the incident angle q): (4.24) Units are [W/m^2]

  4. Daily, Monthly and Annual Insolation • If we integrate IBC (which varies throughout the year) over a day, a month or a year, we find the energy collected (in kWh, for example) per unit area of collector. • The total energy gathered annually doesn’t vary too much with orientation for fixed collectors • However, the month-to-month numbers can vary greatly depending on the orientation • This is an important distinction depending on what type of solar installation is planned • Grid-connected systems can fluctuate monthly, standalone systems should have flatter supply

  5. Daily, Monthly and Annual Insolation • Annual insolation curves are similar for varying collector orientations • South-facing collectors tend to be the best Σ Figure 4.31

  6. Daily, Monthly and Annual Insolation • Daily insolation curves vary with orientation much more than annual curves A collector with S = L has the flattest curve Larger tilt angles get more insolation in the winter, smaller angles get more in the summer Figure 4.32

  7. Improvement Due to Tracking • Adding a tracking system (one- or two-axis) can have large benefits Figure Not in Text • Two-axis only marginally better than one-axis during the summer months Figure:

  8. US Annual Insolation Champaign averages about 4.7 [kWh/(m^2-day)]

  9. Illinois Insolation Data [kWh/(m^2-d)] Daily average = 4.69 [kWh/(m^2-day)] Yearly average = 1.7 [MWh/(m^2-yr)] “Evaluation of the Potential for Photovoltaic Power Generation in Illinois” by Angus Rockett, 2006

  10. Interpreting the Data • Units on insolation maps are [kWh/(m^2-day)] • DEFINE:1-sun of insolation = 1 kW/m^2 • Estimate of the insolation at the Earth’s surface on a bright sunny day with the sun high in the sky • Other values of insolation can be referenced to this standard • 1 sun of insolation for 1 hour (or, 1 hour of full sun) gives 1 kWh/m^2 • Champaign’s yearly average isolation of 4.7 kWh/(m^2-day) can be interpreted as 4.7 hours of full sun per day, on average.

  11. Worldwide Annual Insolation [MWh/(m^2-yr)] Champaign is about 1.7 In 2011 worldwide PV capacity was about 70GW, with about 1/3 in Germany (25GW), 12.8 GW in Italy, 5 GW in Japan, 4.5 GW in Spainand 4 GW in the US http://www.ren21.net/Portals/97/documents/GSR/GSR2012_low%20res_FINAL.pdf

  12. End of Chapter 4 • Questions?

  13. Photovoltaics (PV) Photovoltaic definition- a material or device that is capable of converting the energy contained in photons of light into an electrical voltage and current University of Illinois Solar DecathalonHouse “Gable Home” – 2nd place overall in 2009 "Sojourner" exploring Mars, 1997 Rooftop PV modules on a village health center in West Bengal, India http://www.solardecathlon.uiuc.edu/gallery.html# http://www1.eere.energy.gov/solar/pv_use.html

  14. Photovoltaics • Illinois 2011 Solar Decathlon house “Re_home” • Now resides on South First Street http://www.solardecathlon.gov/past/2011/team_illinois.html#nogo

  15. PV History Edmund Becquerel (1839) Adams and Day (1876) Albert Einstein (1904) Czochralski (1940s) Vanguard I satellite (1958) Today… Cost/Capacity Analysis (Wp is peak Watt) http://www.nrel.gov/pv/pv_manufacturing/cost_capacity.html

  16. PV System Overview • A solar “cell” is a diode • Photopowerconverted to DC • Shadows & defects convert generating areas to loads • DC is converted to AC by an inverter • Loads are unpredictable • Storage helps match generation to load Shadows

  17. Some General Issues in PV • The PV device itself • Efficiency, cost, manufacturability/automated production, testing • Encapsulation • Cost, weight, strength, yellowing, etc. • Accelerated lifetime testing • 30 year outdoor test is difficult • Damp heat, light soak, etc. • Inverter & system design • Micro-inverters, blocking diodes, reliability

  18. What are Solar Cells? Load - + • Solar cells are diodes • Light (photons) generate free carriers (electrons and holes) which are collected by the electric field of the diode junction • The output current is a fraction of this photocurrent • The output voltage is a fraction of the diode built-in voltage p-type n-type Open-circuit voltage Voltage Maximum Power Point Current Short-circuit current

  19. Standard Equivalent Circuit Model Where does the power go? Series resistance (minimize) Photocurrent source Shunt resistance Load Diode (maximize)

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