Solar Panels Are So Widely Used That We Sometimes Take It For Granted, How Does a Panel produce Energy?
We see solar panels and systems everywhere in public space recently, there is a huge buzz around them. We all know the basic concept- the panel converts energy from the sun to electricity. But just how can a static array of photo voltaic cells turn the sunlight into electricity?
To grasp the concept, we will start with understanding the photo voltaic effect.
Light shining on a metal surface makes jump between orbits and then move freely between atoms. When scaled and many electrons are moving in one direction we have what we call an electrical current. By causing an electric field we can cause the electrons to move in the same direction which takes care of the second part. ( For those who would like to read further I recommend).
What are Solar Panels Made of?
The most commonly used silicon solar panels are built as a stack of several layers. Each layer is composed of different materials. All together the layers create the amazing effect of power generating when exposed to the sun
Typically a solar panel consists of the following Six layers.
- Glass
- Encapsulant
- Solar Cells
- Encapsulant
- Backsheet
- An aluminum frame
Glass
The top layer of the panel is glass. This layer serves the purpose of protecting the more sensitive electric parts from the conditions of the environment.
Sunlight easily travel through glass making it a great fit for this mission.
The type of glass we use on solar panels is highly durable and shock resistant.
Protip: it’s a good idea to wash your solar panels from time to time and clean them from the layer of dust that builds on them. The dust layer makes less sunlight go through the panel and takes the panel performance down.
Encapsulant
underneath the glass, we use a layer of an encapsulant that binds the glass to the layer of PV cells below. Encapsulants are designed to be durable in high temperatures and UV exposures. Another important quality of the kind of encapsulant used is that it’s crystal clear in order to allow sunlight to pass on to the layers below. EVA (ethyl vinyl acetate) is currently the most commonly used type of encapsulant in solar panels.
Photo Voltaic Cell (PV)
In this layer, the energy-transferring magic is happening. The PV cells are what we see when looking at the solar panel. Typically they are black or blue and have one of two common shapes.
1. small rectangles (polycrystalline panels)
2. small octagonal squares (monocrystalline panels)
Every solar panel consists of an array of many of those cells ( typically 36-72)
To manufacture a PV cell we use silicon crystal semiconductors.
In Monocrystalline panels, a single crystal of silicon is the base for every PV cell.
Whereas in Polycrystalline panels, multiple silicon crystals combined in the making process are the base of the PV cell. Each comes with its own benefits and could be more suitable for different projects.
Protip: Monocrystalline panels are of higher quality for their higher efficiency in generating energy.
Polycrystalline panels are more affordable due to a cheaper manufacturing process.
The Backsheet
Below the PV cells array, we have another layer the of encapsulant. The backsheet could be visible as what makes the white or black lines in a solar panel. The PV cells have some spaces between them living some room to see backsheet below.
The backsheet helps to seal the panel from the environmental conditions as well as mechanically holds it all together. A combination of a few polymers are the common choice for a backsheet for their good ability to keep moisture outside as well as their economical price.
The Aluminum Frame
To top up we cover the corners of the panel in an aluminum frame, which helps protect the panel and adds mechanical strength to it.
So How Do All Of The Above Layers Generate Power?
After understanding the physical layers combined to form a solar panel, let’s dig into how can this design generate electricity.
To make a long story short most of the magic happens in the silicon solar cells.
When manufacturing a solar panel you would stack the cells in two sub-layers. Charging the upper with a negative charge due to added Phosphorus (meaning more free electrons). As well as charging the lower with positive charge due to added Boron that lowers the number of free electrons resulting in a positive charge.
The charge difference between the two layers forms an electric field. When a particle of sunlight (called a photon) hits the panel, the free electrons start moving in the orientation of the field. They then find themselves attracted to metal conductive plates on the sides of the cells. Those moving electrons go toward the positive side where they meet with connecting wires finally causing an electrical current!
It’s worth mentioning that solar panels generate DC electricity – direct current. The electricity we get from the grid is AC – alternating current. Every grid-connected solar system or even one that is powering regular appliances is using an inverter to gap this difference or by using a battery to locally store the energy.
The output DC current flows to the inverter through electrical wires. The inverter converts it into AC power. The next stop for it is the distribution power that connects to all appliances.
To Conclude Solar Panels Aren’t that Complicated
When comparing solar panels to other clean options for electricity generation solar panels are pretty simple. Solar panels generate clean sustainable energy with no emissions but the manufacturing process and a minimal impact on the environment. As technology improves, systems become more efficient and price tags drop means solar could be a great part of the progress toward a more sustainable world.
Now after seeing the six layers of substances and the theoretical concept you could say you understand how do solar panels work.
