Fig. 4: Projected irradiance onto the unit circle for sunlight tracking systems.
From: Improved silicon solar cells by tuning angular response to solar trajectory
a Ideal 2-axis tracker confining direct and 2.9o circumsolar radiation to the unit circle centre. b Ideal 1-axis tracker on EW-axis, with a simple direct and circumsolar irradiance pattern moving E to W across the unit circle. c More common 1-axis tracker on NS-axis, with projected sun-paths latitude dependent, moving N to S across the module and back (northern hemisphere), shown both for 40o latitude and at the equator (dashed sun positions, giving smallest sun-path). d 1-axis tracker on NS-axis (latitude 40o) with backtracking25 to prevent adjacent module shading. Modules start the morning horizontal, tilting towards their ideal tracking position as the sun’s altitude increases, then back towards horizontal in the evening.
