PV System Design and Installation

1. PV System Design and Installation LO 5A - PV Module Fundamentals

2. PV Module Fundamental (15% of test questions) 5.1. Explain how a solar cell converts sunlight into electric power 5.2. Label key points on a typical IV curve 5.3. Identify key output values of solar modules using manufacturer literature 5.4. Illustrate effect of environmental conditions on IV curve 5.5. Illustrate effect of series/parallel connections on IV curve 5.6. Define measurement conditions for solar cells and modules (STC, NOCT, PTC) 5.7. Compute expected output values of solar module under variety of environmental conditions 5.8. Compare the construction of solar cells of various manufacturing technologies 5.9. Compare the performance and characteristics of various cell technologies 5.10. Describe the components and construction of a typical flat plate solar module 5.11. Calculate efficiency of solar module 5.12. Explain purpose and operation of bypass diode 5.13. Describe typical deterioration/failure modes of solar modules 5.14. Describe the major qualification tests and standards for solar modules

3. How PV modules work

4. Shading issues Sun – Radiant Energy PV module

5. Silicon Atom Four electrons in outer shell Reference 3

6. Crystalline Silicon Models Reference 2

7. Definitions - Electrons and Holes

8. Step 1 – Photoelectric effect When sunlight (photon) hits silicon atom, an electron in its outer shell can be “liberated” and start moving throughout the crystalline structure. A “hole” with a positive charge is “left” behind at the silicon atom that lost its electron. Recombination - Eventually free electron combines with another hole. Reference 3

9. Step 2 – Doping process Doping - Process of adding impurities to prevent free electrons randomly “moving” in PV cell.

10. Addition of Phosphorus Addition of phosphorous creates N-type (negative) semiconductor material

11. Addition of Boron Addition of boron creates P-type (positive) semiconductor material

12. Step 3 – Putting PV cell together

13. Electrical Field at P/N Junction Reference 3 Free electrons from phosphorus atom cross over to fill “holes” in boron atoms. This creates a permanent electric field at p/n junction.

14. Space Charge Zone Depletion Region

15. Step 4 – Sunlight hits PV module and current (electron movement) occurs Reference 3

16. Typical PV Cell Reference 2

17. How PV Cells Work Illustration http://projectsol.aps.com/inside/inside_pv.asp

18. Solar Cell Types Silicone Crystalline Cells a) Monocrystalline b) Polycrystalline Thin Layer Cells a) Amorphous silicon b) CIS c) CdTe Reference 2

19. Crystalline Silicone Polycrystalline Monocrystalline Reference 2

20. Thin Film Cell Examples Reference 2

21. Differences in Cell Type Efficiencies

22. Advantages / Disadvantages of Cell Types Crystalline Silicone Highest cell efficiencies Well established manufacturing technology Durable product Thin Film Cells Con’s Less efficient than crystalline silicon Harder to control / MPPT tracking devices (flatter IV curve) Pro’s Wider spectral response (sunlight wavelengths) More efficient at low irradiance levels Use less energy and material to produce More flexible than crystalline silicone More tolerant of shading issues

23. Typical PV Module Construction Reference 2

24. Typical PV module energy losses Typical Polycrystalline Cell Efficiency PV output = 12 to 15% Solar Irradiance 3% - Reflection and shading by front contacts 23% - Insufficient photon energy of long-wave radiation 32% - Surplus of photo energy of short wave radiation 8.5% - Recombination losses 20% - Electrical gradient in cell, especially in space charge zone 0.5% - Due to serial resistance (electric heat loss) Reference 2