Sun Angles  Impact the amount of Insolation  Daylight Hours Seasonal Seasonal October – March October – March Low – SunLow – Sun April – September April – September High - SunHigh - Sun  Solar declination Latitude where sun is directly overhead (90°) Sub Solar Point  Zenith Angle Angle between 90° and sun at noon  Sun Angle Angle of the sun above the horizon at noon

Sun Angles  Zenith Angle + Sun Angle = 90°  SO What is Tuscaloosa’s noon sun angle on June 21 st ? What is Tuscaloosa’s noon sun angle on June 21 st ? Let’s practice Let’s practice  Step 1 Determine declination of sun for that date  Step 2 Find noon sun angle Difference in ° between location’s latitude and SS point then subtract from 90

The Analemma

Daylight Hours  How does sun angle impact the amount of daylight hours at different latitudes?  Online calculator

Solar Intensity  Intensity = Sin (A) Sin = sine Sin = sine A = sun angle A = sun angle  90 = 100% efficiency  80 = 98%  45 = 71%  20 = 34%

Run Applet

Insolation by Latitude

NET RADIATION