Solar panels, also known as “PV panels”, convert energy from the sun into electricity that is used to power electric loads. When light from the sun, in the form of particles called photons, reaches a solar panel, it creates an electric current. But what’s happening on a molecular level?
This artice takes a closer look at how solar panels convert sunlight into electrical energy.
What are solar panels made of?
Solar panels are made from silicon, also known as “Silica Sand”. This silicon must be purified and treated in a very specific way to allow it to convert sunlight into electricity.
There are three main reasons we use silicon to make solar panels:
- Silicon is abundant and easy to find
- It’s cheap to produce
- It’s a very efficient semiconductor
What is a semiconductor?
A semiconductor is a material that conducts electricity better than an insulator, but not as well as a conductor. In other words, it’s in between a conductor and an insulator.
Each silicon atom has 4 electrons in the outer shell (conductive level).
Atoms connect to each other via shared electrons in a process called covalent bonding. This means that when two silicon atoms are bonded together, the atoms share their electrons so that each atom has a full outer shell.
As each atom has a full outer shell, in ideal conditions, the material acts as an insulator. However, when impurities (like phosphorous or boron) are added to the silicon, it creates a defect in the lattice.
These defects allow electrons to jump from one atom to the next, creating a flow of electricity.
How do solar panels convert sunlight into electricity?
Now that we know a little bit about silicon and semiconductors, let’s take a look at how solar panels convert sunlight into electricity.
Light is made of tiny particles called photons.
These photons have masses, speeds, and colors that correspond to the energy they contain.
When a photon hits a silicon atom, it transfers its energy to an electron in the atom in a process called a photovoltaic effect.
If the transferred energy is greater than the electron’s binding energy, the electron will break free from the atom.
Once the electron is free, it flows through the silicon material in the same way that electricity flows through a wire.
This flow of electrons creates an electric current, and that’s what we use to power our homes and appliances.
What does solar panel efficiency mean?
Efficiency is a measure of how well a solar panel can convert sunlight into electrical energy. The higher the efficiency, the more electricity the solar panel will produce for every unit of sunlight it absorbs.
Most commercial solar panels have efficiencies of around 15-20%. This means that for every 100 watts of sunlight that reaches the panel, the panel will generate 15-20 watts of electrical energy.
What affects solar panel efficiency?
There are several factors that can affect a solar panel’s efficiency.
The most obvious factor is the amount of sunlight the panel receives. The more sunlight the panel absorbs, the more electricity it will generate.
Another factor is the temperature. Solar panels work best when they are cool. If they are exposed to high temperatures, their efficiency will drop.
Finally, solar panels can be affected by shading. If part of the panel is shaded, its efficiency will be reduced.