Question

How does solar energy convert heat energy into electrical energy?

Answer 1

Solar Energy:

1. Solar energy is the energy that is obtained from the sun.
2. The main form of energy obtained from solar energy is light and heat energy.
3. Solar energy can be utilized in various ways.
4. One of the most utilized ways is converting the heat energy obtained from the sun into electrical energy.

Types of Solar Energy:

Solar energy is classified into two types based on the way in which solar energy is utilized

1. Active Solar Energy - In these systems, solar energy is used to heat up fluid (liquid or air).
2. Passive Solar Energy - In this system, a house is kept cool or heated as per comfort by the use of passive means, without the use of mechanical equipment.
3. Electricity from Solar Energy - In this system, with the help of photovoltaic cells, solar energy is converted to electrical energy.

Photovoltaic Cell or Solar Cell:

1. A photovoltaic cell is a device that operates on the principle of the photovoltaic effect.
2. The potential barrier in an open-circuited non-illuminated p-n junction adjusts itself so that the resultant current is zero.
3. When the junction is illuminated, electron-hole pairs are generated on each side of the junction.
4. As the minority carriers (electrons of p-side and holes of n-side) move down the potential barrier, it causes an increase in reverse current.
5. But since the diode is in an open circuit, the resultant current must be zero.
6. So the majority current must increase by the same amount as the minority current.
7. The increase in majority current is affected by the decrease in barrier height in the presence of incident light.
8. As a result, a potential difference develops across an open-circuited illuminated p-n junction.
9. Actually, the potential difference develops due to the accumulation of excess majority carriers in their respective regions.
10. This is known as the photovoltaic effect.
11. A photovoltaic cell uses this effect to convert light energy into electrical energy.
12. When sunlight is used as an incident photon, photovoltaic cells are called solar cells.
13. A solar cell is basically a p-n junction with a large surface area that can convert solar radiation directly into electrical energy.
14. The construction of a basic solar cell is shown in the figure below.
15. It consists of a shallow p-n junction, a front ohmic contact either along the edge or around the perimeter, and a back ohmic contact that covers the entire back surface.
16. The top surface is designed to expose a maximum portion of it to the incident sunlight.
17. The surface is also coated with appropriate material to reduce reflection and decrease surface recombination.
18. The surface layer of n-type material is made extremely thin mm) such that light can penetrate the junction.

Diagram:

Hence, solar energy converts heat energy into electrical energy by using photovoltaic cells.