Step 3 Determine Collector Tilt Angles

Assumption

• Site location is 20° N

• Find tilt angle when sun is over:

  1. Equator

  2. Tropic of Cancer

  3. Tropic of Capricorn

Step 1 Draw Template

Step 3 Mark site location

1. Solar panel always faces the sun.

2. Sun line is the line from sun to solar panel bottom

3. If the site locates exactly on Equator/ Tropic of Cancer/ Tropic of Capricorn

   • Solar panel lies horizontal to face the sun

   • Sun line = Vertical line from template to sun

Step 5 Mark angles

1. α = angle between template --> sun line = solar altitude angle at site

   • α = 90° - θ  (Site at Equator)

   • α = 90° - θ - 23.45 (Site at different hemisphere with sun)

   • α = 90° - θ + 23.45 (Site at same hemisphere with sun)

   • Final answer: 

     • If α < 90° : α looking [opposite hemisphere of site]

     • If α > 90° : However, physically this actually means α = [180 - α ] looking [same hemisphere of site]

2. β = angle between template --> back of solar panel = tilt angle

   • β = 180° - 90° - α = 90° - α (Normal right triangle calculation)

   • Final answer:

     • β looking [opposite hemisphere of site]

     • In general, usually looking direction of β and α are same.

When sun is over Equator,

α = 90° - 20° = 70° looking S

β = 90° - 70° = 20° looking S 

When sun is over Tropic of Cancer,

α = 90° - 20° + 23.45° = 93.45° looking S

However, physically this actually means α = [180° - 93.45°= 86.55°] looking N

β = 90° - 86.55° = 3.45° looking N 

When sun is over Tropic of Capricorn,

α = 90° - 20° - 23.45° = 46.55° looking S

β = 90° - 46.55° = 43.45° looking S