Solar cell efficiency videos and transcripts

Solar cell efficiency was the topic of investigation for Sunny (Grade 5 boy).  This topic was initially "Solar panels" until session 15.

Prior knowledge video

My topic is solar panels and what I know about them is that they take something from the Sun and make it into energy that can power stuff like, umm, and, it saves you money on electricity bills.

And that's most of the, no that's all of the stuff I know about solar panels.



Completed explanatory animation

Solar panels are made up of photovoltaic cells.

A photovoltaic cell converts light energy into electricity.

At the heart of a photovoltaic cell is an NP junction where negative and positive plates made of silicon and other materials are placed close together.  Electrons want to jump across from the Negative to the Positive side.  This force is known as voltage but energy is still needed to make electrons jump across.

Energy in the form of photons from sunlight enables electrons to jump across which creates the flow of electricity, which is known as current.

Even the best solar cells only achieve around 40% efficiency.

There are several things that can improve the efficiency of solar cells:

Silicon is very shiny so most of the sunlight is reflected which is a waste of energy.  This is why solar panels have a dark non-reflective coating so that more light flows into the cell.

Light can have different amounts of energy just like it can have different colours.

Most solar cells are designed to create electricity with only a small amount of light but this means that only a low voltage is produced.

The strength of the voltage known as 'Band gap energy' depends on how much energy is required for electrons to jump across the NP junction.

In strong sunlight you get extra current but the voltage doesn’t really increase. New research involves multi-junction cells which have more than one electric field.  This allows the panel to operate in low light and also take advantage of stronger light with increased current and voltage.

Director's commentary

Halfway through my animation I slightly changed my topic from "Solar panels" to "Solar cell efficiency".

Originally I had an idea of a stadium, or a theatre of some sort, and electrons jumping from one seat to another because someone had moved to go somewhere.  After I changed that we made it more realistic with electrons jumping across from one bar that said "Negative" to one bar that said "Positive".

To make the animation about solar cells, I had to learn about other things like voltage, current and electricity, which I only knew some about at the start of the animation.

I figured out that the solar panels are dark because, if they’re not, the light bounces off and when it’s dark it gets absorbed so the energy isn’t wasted.

In real life the band gap energy doesn’t mean that the negative and positive sides are further apart (like it looks like in the animation) but that was a good way to show it so that people would understand.

My topic was so complicated that, although it’s still the longest, we had to remove some of the information that we were going to include at the start.

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