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I Calculation of daily solar insolation

  1. Jul 17, 2017 at 5:13 AM #1
    Hi all,

    I'm trying to calculate the daily solar insolation (integrated solar irradiances from sunrise to sunset) for a given location and day of the year. For latitude 43.2° and April 15th, I get:

    H0 = (solar constant * scale factor for intra annual variation of sun-earth distance * 86400 seconds/pi) * (cos(latitude) * cos(declination) * sin(hour angle sunset) + (hour angle sunset * pi/180)*(sin(latitude)*(sin(declination))

    or with numbers:

    H0 = ((1368*0.99226178414418)*(86400/pi))*(cos(43.2°)*cos(9.6423°)*sin(99.1805°)+(99.1805°*pi/180)*sin(43.2°)*(sin(9.6423°)) = 3.39E7 J/day.m2

    However, when I try to check the result with online calculators, they say the result should be 2.65E7 J/day.m2 ...

    Can anyone please check and help me out if and what I am doing wrong? It would be of very great help!

    Thank you!
  2. jcsd
  3. Jul 17, 2017 at 6:11 AM #2


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    I can't say I entirely follow your calculations, but the end result difference looks in the ballpark of what you'd get if you corrected for albedo - which you don't seem to have done.
  4. Jul 17, 2017 at 6:52 AM #3

    Hi, calculations were based on Part 4: Irradiation Calculations | ITACA:

  5. Jul 17, 2017 at 7:47 AM #4


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    What calculators are these? I'm getting 3.39E7 out of wolfram alpha.
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