1. Solar Resource Part 2 August 27, 2015

2. Session 03 Components Wrap-up of Session 02 The Solar Resource o Tracking the sun o Orientation considerations 2

3. Learning Outcomes An elementary understanding of the solar resource Recognition of impact of solar system orientations 3

4. Value to participants An understanding of the solar resource leads to proper design of a solar photovoltaic system 4

5. The Solar Resource – Earth’s orbit Messenger & Ventre, Fig 2.4

6. The Solar Resource – The celestial sphere Markvart, Solar Electricity, Fig 2.6

7. Motion of Sun Diagram – Perspective view of daily motion 7

8. Motion of Sun Diagram – Example #1 8 North Pole Summer Solstice Equinox Winter Solstice 23.5 o zenith latitude Arbitrary Location N S

9. Motion of Sun Diagram – Example #2 9 Tropic of Cancer Latitude = 23.5 o North Pole Summer Solstice Winter Solstice Equinox 23.5 o zenith N S

10. The Solar Resource 10 Sun

11. The Solar Resource – altitude and azimuth 11 Markvart, Solar Electricity, Fig 2.7b

12. The Solar Resource - SunChart 12 http://solardat.uoregon.edu/SunChartProgram.html

13. The Solar Resource – altitude, azimuth, hour angle Messenger & Ventre, Fig 2.6

14. The Solar Resource – altitude, azimuth, hour angle Markvart, Solar Electricity, Fig 2.7a

15. The Solar Resource – altitude vs azimuth Messenger & Ventre, Fig 2.8

16. The Solar Resource As we have seen, the solar resource changes continuously, month to month, day to day, hour to hour, because of the movement of the earth This has an impact on the deployment of the photovoltaic modules. The solar resource is optimally used when the modules have perpendicular orientation to the sun rays One can construct a mounting system for the modules that continuously changes its orientation to match the sun’s position (a tracking system) OR One can mount the modules at a constant orientation that represents an engineering compromise (a fixed system) 16

17. The Solar Resource – Module orientation

18. The Solar Resource – Orientation Effects Both tracking and fixed mounting options have been used in real world photovoltaic systems The choice between the two is often based on economic considerations When a fixed mounting system is used, the following guidelines are usually chosen (in the northern hemisphere): o The modules point to the south (azimuth angle of 0 o ) o The modules have a tilt angle (from the horizon) equal to the local latitude 18

19. The Solar Resource - Calculations A calculation of the total energy produced by a photovoltaic system, with PV modules in fixed orientation, must take into account the local solar energy input, the orientation angles of the PV array, and the local latitude. This calculation can be carried out with PVWatts: o http://pvwatts.nrel.gov This program, constructed at the National Renewable Energy Laboratory (NREL), can be used for many sites around the globe and is freely available 19

20. The Solar Resource 20 PVWatts calculation: Comparison of two orientations in SW USA

21. The Solar Resource – Spacing Calculation