Sun AnglesSun Angles

Impact the amount of Impact the amount of InsolationInsolation

Daylight HoursDaylight Hours SeasonalSeasonal October – MarchOctober – March

• Low – SunLow – Sun April – SeptemberApril – September

• High - SunHigh - Sun

Solar declinationSolar declination Latitude where sun is Latitude where sun is

directly overhead (90directly overhead (90°)°)• Sub Solar PointSub Solar Point

Zenith AngleZenith Angle Angle between 90° Angle between 90°

and sun at noonand sun at noon Sun AngleSun Angle

Angle of the sun Angle of the sun above the horizon at above the horizon at noonnoon

Sun AnglesSun Angles

Zenith Angle + Sun Zenith Angle + Sun Angle = 90Angle = 90°°

SOSO What is Tuscaloosa’s What is Tuscaloosa’s

noon sun angle on noon sun angle on June 21June 21stst??

Let’s practiceLet’s practice

Step 1Step 1 Determine declination Determine declination

of sun for that dateof sun for that date

Step 2Step 2 Find noon sun angleFind noon sun angle

• Difference in Difference in °° between between location’s latitude and location’s latitude and SS point then subtract SS point then subtract from 90from 90

The The AnalemmaAnalemma

Daylight HoursDaylight Hours How does sun angle How does sun angle

impact the amount of impact the amount of daylight hours at daylight hours at different latitudes?different latitudes?

Online calculatorOnline calculator

Solar IntensitySolar Intensity

Intensity = Sin (A)Intensity = Sin (A) Sin = sineSin = sine A = sun angleA = sun angle

90 = 100% efficiency90 = 100% efficiency 80 = 98%80 = 98%

45 = 71%45 = 71% 20 = 34%20 = 34%

Run AppletRun Applet

Insolation by LatitudeInsolation by Latitude

NET RADIATIONNET RADIATION