Energy is an essential resource in our everyday lives. From our mobile phones to the air conditioners found in shopping malls, anything that requires electricity to run needs electrical energy. This energy needs to come from somewhere since energy cannot be created out of thin air. It is well known that most of the electricity comes from the chemical energy in fossil fuels. However, in this article, we shall take a look at another source: the Sun!
The Sun is where we get heat as we live on planet Earth. To harness the energy from the Sun (also known as solar energy), we can use solar panels to capture the solar energy that comes from the Sun.
What are solar panels?
Solar panels are devices that convert light from the Sun into electricity, which can then be used for objects that require electricity to function. Solar panels consist of multiple solar cells, which are made of semiconductor materials such as silicon.
How do solar panels capture solar energy?
To know how these solar panels capture solar energy, we have to look into the inner workings of a solar cell.
Structure of solar cells
Let us take a look at the atomic structure of silicon, a material that is commonly used for solar cells. As a silicon atom only has 4 electrons on its valence shell, the atom would need to bond with others to achieve a stable electronic configuration. As such, multiple silicon atoms bond together to share electrons such that every silicon atom would have 8 valence electrons on the valence shell.
If solar cells were only made of silicon, not much reaction would occur, as all the electrons would be used in bonding. Therefore, in addition to silicon, other materials such as phosphorus and boron are used to create specific effects. These impurities among the silicon atoms allow us to form the n-type and p-type materials used in solar cells.
In the n-type material, both silicon and phosphorus atoms are present. Silicon atoms have four valence electrons, whereas phosphorus atoms have five. When these atoms bond with each other, an extra electron that does not participate in bonding is left unattached. This free electron becomes important later.
In the p-type material, both silicon and boron atoms are present. However, boron atoms have only three valence electrons. When these atoms bond with each other, a 'missing' electron, also known as a hole, is created.
When the two materials are combined, the electron and the hole are attracted to each other. The electron moves towards the p-side, and the hole moves towards the n-side, creating an electric field in the region known as the p-n junction.
The process
Solar cells are also known to be photovoltaic cells as the process of converting solar energy to electrical energy is called the photovoltaic effect.
Fun fact
Light - and by extension, everything on the electromagnetic spectrum - is actually made of particles, also known as photons. Since sunlight is also light, when sunlight hits the solar cell at the p-n junction, energy from the photons is transferred to the electrons in the p-n junction. Remember that these electrons belonged to the valence shell of the atom? With this energy from the photon, this causes the electrons to get excited and jump to a higher energy state known as the conduction band, hence allowing them to move around.
However, due to the electric field established at the p-n junction, the electrons cannot freely move towards the p-side to fill the holes present. Instead, the freed electrons head in the opposite direction, back to the n-side. The holes created by these excited electrons also move towards the p-side. As a result, with an electron flow and a hole flow going in opposite directions, a current is created in the cell. With current, there is electrical energy. If you were to connect an electric contact between the two semiconductor materials (one on the n-side, the other on the p-side) and a cable to connect the two electric contacts and a light bulb, you would see that the light bulb lights up!
Conclusion
In summary, solar cells work by using concepts of semiconductors to capture solar energy and convert it into electrical energy that we all require. This method of obtaining electrical energy is from a renewable resource and therefore has a lesser impact on the environment than obtaining electrical energy from fossil fuels.
Works cited
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Hanania, J., Stenhouse, K. and Donev, J. (2015). Photovoltaic effect - Energy Education. [online] Energyeducation.ca. Available at: https://energyeducation.ca/encyclopedia/Photovoltaic_effect [Accessed 27 Feb. 2024].
MrSolar (2018). What Is A Solar Panel? [online] Mrsolar.com. Available at: https://www.mrsolar.com/what-is-a-solar-panel/ [Accessed 26 Feb 2024].
Sci Pills (2020). Photovoltaic effect. [online] www.youtube.com. Available at: https://youtu.be/w52vMeeT7Kk?si=71BpnzoRMRWlNVYC [Accessed 26 Feb. 2024].
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Solar Energy Technologies Office (2022). Solar Photovoltaic Technology Basics. [online] Energy.gov. Available at: https://www.energy.gov/eere/solar/solar-photovoltaic-technology-basics [Accessed 27 Feb. 2024].
World Nuclear Association (2017). Where does our electricity come from? - World Nuclear Association. [online] World-nuclear.org. Available at: https://world-nuclear.org/nuclear-essentials/where-does-our-electricity-come-from.aspx [Accessed 23 Feb. 2024].
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