1. Photovoltaic Systems Engineering
SEC598
Photovoltaic Systems Engineering
(SEC501 Solar Engineering and Commercialization, I)
Session 03
The Solar Resource
August 24, 2017

2. Session 03 Components The Solar Resource Definitions Solar radiation
Tracking the sun
Orientation considerations

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

4. The Solar Resource – earth’s orbit
Messenger & Ventre, Fig 2.4

5. The Solar Resource – earth’s orbit

6. The Solar Resource – The annual motion from the perspective of the celestial sphere
d - declination
Markvart, Solar Electricity, Fig 2.6

7. The Solar Resource – The annual motion from the perspective of the celestial sphere
Häberlin, Photovoltaics, Fig 2.3

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

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

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

11. The Solar Resource – Connection to Declination and Latitude
Häberlin, Photovoltaics, Fig 2.2

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

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

14. The Solar Resource – Definitions
fL Latitude, the angular location north or south of the equator, north positive, -90o < fL < +90o
d Declination, the angular position of the sun at solar noon with respect to the plane of the equator, o < d < o. The inclination of the earth to its orbital plane is 23.45o
a Altitude, the angle between the horizontal plane and the direct line to the sun, 0 < a < 90o
qz Zenith angle, the angle between the normal to the horizontal plane and the direct line to the sun, 0 < qz < 90o. It is the compliment to the altitude
y Azimuth, the angular deviation of the projection of the sun onto the horizontal plane with zero due south, east negative, west positive, -180o < y < +180o

15. The Solar Resource – Formulas
Declination
The solar hour angle

16. The Solar Resource – Formulas
Altitude and Azimuth (parametric equations)
The sunrise angle

17. The Solar Resource – Connection to Altitude and Azimuth

18. The Solar Resource – Module with southern orientation
Markvart, Solar Electricity, Fig 20.7

19. The Solar Resource – altitude vs azimuth
Häberlin, Photovoltaics, Fig 2.5

20. The Solar Resource - SunChart

21. The Solar Resource – arbitrary module orientation

22. The Solar Resource – Formulas
Relation between incidence angle and other solar angles

23. The Solar Resource – Definitions
fL Latitude, the angular location north or south of the equator, north positive, -90o < fL < +90o
b Module tilt, the angle between the horizontal plane and the normal to the module plane, 0 < b < 90o
qi Incident angle, the angle between the normal to the module plane and the direct line to the sun, 0 < qi < 90o.
yW Wall angle, the rotation (orientation) of the module plane, -180o < yW < +180o

24. 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)