How Electricity is Generated by a Solar Cell

What is a Solar PV Cell and how it works?

Today in this article we are going to answer the following questions:

1. How electricity is generated by a solar cell?
2. What is Global Irradiance?
3. What are the components of Global Irradiance?
4. What is the role of Global Irradiance in the production of electricity?

A Solar Photovoltaic Cell or simply Solar PV System is a system that generates electricity using Solar Irradiance. The solar energy is produced by fusion. Inside the sun, hydrogen atoms are combined to make helium (He). Consequently, part of the Hydrogen mass is deducted and converted into energy according to the Einstein equation of energy.

According to the researches, Sun through enough energy for whole planets need for 1 year just in one hour. But we cannot convert all the energy from the sun into usable energy because:

1. It’s distributed to the whole planet.
2. It’s divided into seasons and day/night and also dependent on weather conditions.
3. We don’t have the technology to recover all the energy delivered by the sun.

In Earth’s atmosphere average irradiance value is around 1367 W/m2. Which is shown below in the chart for every month. Vertical Scale is for Irradiance in W/m2 and the horizontal scale is for months of the year.

But this average energy does not reach the surface of the earth due to the atmospheric effects. Energy reaches onto the surface of the earth is divided into three portions:

1. Major Portion of the energy arrives directly to the earth surface.
2. Some portion reaches in the diffused form. 
3. Some portion of the energy is lost due to reflection and absorption

Solar Radiation on a tilted Plane and Oriented Plane

The Global Irradiance (G) is comprised of the following three components:

1. Direct Irradiance which is measured on a plane which is normal to the sun rays is donated by “B”.
2. Diffused Irradiance is measured on a plane which is horizontal to the sun rays is donated by “D”.
3. Reflected Irradiance is also measured on a horizontal plane and donated by “R”.

Taking all the above components in mind the formula to calculate the Global Irradiance G is:

Here:

1. 𝜃 is the angle of incidence of sunrays on tilted plane
2. β is the tilt angle of the plane

The unit of Irradiance is 𝑊⁄𝑚2⁄ OR 𝐾𝑊⁄𝑚2⁄

The unit of Radiation is 𝑀𝐽⁄𝑚2⁄ OR 𝐾𝑊ℎ⁄𝑚2⁄

Therefor “G” the Global Irradiance is directly proportional to the Electricity generated by a solar cell. So if global irradiance “G” increases then electricity generated by solar cell increases and if global irradiance decreases then electricity generated by solar cell also decreases.

Click Here for Solar Power Plant in UAE 01