You are currently viewing Solar energy

Solar energy

We will continue wiht theorethical observation with solar usage therms

Solar constant

A solar constant is a measurement of the solar electromagnetic radiation available in a meter squared at Earth’s distance from the sun. It can be obtained from satellite measurements and from
Stefan-Bolzman constant. In January, when the sun is closest to the earth, the solar heat on the outer edge of the earth’s atmosphere is about 1400 W/m.2and when the sun is the farthest away, on July 4, it is about 1330  W/m2
We will assume for our calculations that it is 1377 W/m2


Extraterrrestirial Radiation I o

The distance between the Earth and the Sun changes during the year.
The solar radiation at the top of the atmosphere is called “extraterrestrial radiation.”
Due to the change in the distance between the Earth and the Sun, the extraterrestrial radiation is changing.

Flux of solar radiation IB

The flux of solar radiation which in the form of direct radiation reaches the earth’s surface is less than Io due to absorption and dispersion in the atmosphere. The estimation of irradiation on the earth’s surface is given by Beer-Lambert law. This measurement can be represent as  the energy of solar radiation that falls normally per square meter per unit time the surface of the Earth..

3 types of radiation

Solar energy is transmitted through three types of radiation:

  • Direct IB
  • Diffuse I
  • Reflected. IR

Direct component I BC

To calculate the direct radiation component, it is necessary to calculate the incident angle under which direct solar rays fall on the observed module. This angle is a function of the altitude, azimuth angle, and tilt of the module.

Difuse component IDC

3 type radiation

When the sun’s rays pass through the atmosphere, a part of that radiation is scattered when it encounters clouds or dust particles. Considering the stochastic characteristic of that process, it cannot be considered that this radiation component has the same radiation from all directions. If the module were placed in a horizontal plane, then this component would reach the maximum value that can be used on a cloudy day.

Reflected component IRC

Solar rays that fall on the earth are partially reflected, so the intensity of the reflection depends on the surrounding surface. The qualitative measure of reflection ranges from 0.1 for asphalt to 0.8 for snow.

The total radiation reaching the module consists of three components: direct , difuse and reflected.


Algorithm and functions

The SPAC ( solar panel angle calculator ) application uses the following dependency functions for calculation

And we have a secret spice of our kitchen that we use with calculation the ideal angle  for fixed panels . That is the mean monthly sunshine hours for each city in the drop-down menu for selecting the city. Chears!

Miroslav Mitić

Mechanical engineer and programmer for 25 years. Solar energy expert

This Post Has One Comment

  1. Nemanja Markovic

    Correct explanation

Leave a Reply