I am currently modeling a solar tracker in MATLAB. But I am confuse about solar irradiance. Actually what is the difference between monthly, daily and hourly solar radiation? Which one is more accurate to test out the tracker? I mean my project is only to test the efficiency. It won't last for a very long time to do the observation.

  • 6
    \$\begingroup\$ What are you asking? The difference between months, days and hours ... \$\endgroup\$
    – Solar Mike
    May 24, 2018 at 14:05
  • \$\begingroup\$ What's your data source? \$\endgroup\$
    – LShaver
    May 24, 2018 at 14:08
  • \$\begingroup\$ If you're trying to utilize this solar tracker to ensure the maximum amount of power for a solar panel, then I can think of two algorithms: 1) This is simple (assuming that you live in the Northern hemisphere). You know that the length of the days in winter are far shorter than the days in the summer. You can have a separate day duration for summers and winters. 2) This one is more tricky: Creating a neural network and a learning machine. You can have the solar tracker locate where the sun is and try to adjust its position in real time. \$\endgroup\$
    – user103380
    May 24, 2018 at 14:40
  • 3
    \$\begingroup\$ @KingDuken - winter days are shorter than summer days in the Southern hemisphere too ... \$\endgroup\$
    – brhans
    May 24, 2018 at 14:47
  • 1
    \$\begingroup\$ You want to simulate something you know little about? You should study the subject before trying to write a simulator. You can't simulate something if you don't understand it. So start with: Irradiance is about 1362 W/m^2 in space. Due to Earth's Bond albedo about 31% of that is lost as a global average figure. You will need to calculate the sun's continually changing altitude during each day (latitude, time of year, time of day, etc) and account for other factors (local high altitude vs low altitude cloudiness measures vs time of year.) \$\endgroup\$
    – jonk
    May 24, 2018 at 17:20

2 Answers 2


as you are working on a Solar Tracker, you want to be concerned with the shortest time measurement as the purpose of the tracker is to identify and follow the area of sky with the highest solar radiance (this will always be where the sun is on a clear day). Between your choices, hourly is the shortest for simulation.

In real life operation, a shorter interval is necessary because panels lose efficiency by a noticeable amount over a 15 minute cycle; and, because you do not want to have micro-adjustments due to short transit cloud formation as that wastes energy in moving the array for lesser results. Your tracker needs to have enough intelligence built in to know if the change in solar radiation is just due to cloud, an obstruction or sunset.

Good luck.


You should be able to model the path of the sun across the sky, lots of info about this and here is a link to one possible interesting article :

pv orientation


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