1. HOW DOES THE LATITUDE OF
A LOCATION IMPACT THE
INSOLATION THAT IT
RECEIVES?

2. LATITUDE AND ZENITH ANGLE AT NOON ON MARCH
AND SEPTEMBER 21.
SUN N
Equator
Center of
Earth S

3. LATITUDE AND ZENITH ANGLE AT NOON ON MARCH
AND SEPTEMBER 21.
SUN
North Pole
Latitude = 90°N
Lat. = 90°
Equator
South Pole
Latitude = 90°S

4. LATITUDE AND ZENITH ANGLE AT NOON ON MARCH
AND SEPTEMBER 21.
SUN
Z = 90°
North Pole
Latitude = 90°N
Lat. = 90°
Equator
South Pole
Latitude = 90°S
Z = 90°

5. LATITUDE AND ZENITH ANGLE AT NOON ON MARCH
AND SEPTEMBER 21.
SUN
Southampton, UK
Latitude = 52°N
Equator
Punta Arenas, Chile
Latitude = 52°S

6. LATITUDE AND ZENITH ANGLE AT NOON ON MARCH
AND SEPTEMBER 21.
SUN
Southampton, UK
Latitude = 52°N
Z = 52°
Equator
Lat = 52°
Punta Arenas, Chile
Latitude = 52°S

7. LATITUDE AND ZENITH ANGLE AT NOON ON MARCH
AND SEPTEMBER 21.
SUN
Z = 52°
Equator
Lat = 52°
Geometry:- “Transversal Postulate.”
Angle of Latitude = Noontime Zenith Angle

8. LATITUDE AND ZENITH ANGLE AT NOON ON MARCH
AND SEPTEMBER 21.
SUN
Gainesville
Latitude = 29.5°N
Z = 29.5°
Lat = 29.5°
Equator
Durban, SA.
Latitude = 29.5°S

9. LATITUDE AND ZENITH ANGLE AT NOON ON MARCH
AND SEPTEMBER 21.
SUN
Quito, Ecuador
Latitude = 0°
Equator
Lat = 0°
Z = 0°

10. CAN WE QUANTIFY THIS EFFECT OF ZENITH ANGLE AT NOON AND LATITUDE?
SUN N
Imaginary solar
collector of
1 m2 S

11. Ten parallel rays representing the solar constant (345Wm-2)
SUN

12. SUN North and South Poles (90°)
Z = 90°: 0/10 Rays intercepted = 0/10*345 = 0Wm-2

13. SUN Southampton and Punta Arenas (52°)
Z = 52°: 6/10 Rays intercepted = 6/10*345 = 207 Wm-2

14. SUN Gainesville and Durban (29.5°)
Z = 29.5°: 9/10 Rays intercepted = 9/10*345 = Wm-2

15. Quito (0°)
SUN
Z = 0°: 10/10 Rays intercepted = 10/10*345 = 345 Wm-2

16. SUN Cos (90) = 0 0 * 345 = 0 North and South Poles (90°)
Z = 90°: 0/10 Rays intercepted = 0/10*345 = 0Wm-2

17. SUN Southampton and Punta Arenas (52°) Cos (52) = 0.62
0.62 * 345 = 210
Z = 52°: 6/10 Rays intercepted = 6/10*345 = 207 Wm-2

18. SUN Gainesville and Durban (29.5°) Cos (29.5) = 0.87 0.87 * 345 = 310
Z = 29.5°: 9/10 Rays intercepted = 9/10*345 = Wm-2

19. Quito (0°)
SUN
Cos (0) = 1.00
1.00 * 345 = 345
Z = 0°: 10/10 Rays intercepted = 10/10*345 = 345 Wm-2

20. ANSWER Q = Cos(Z) * S Where Q = Quantity of insolation (Wm-2)
Z = Zenith angle (noontime value controlled by latitude)
S = Solar constant (345 Wm-2)