Prior knowledge video |
Transcript |
Researcher's commentary |
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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.
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This student is very descriptive with both his commentary and his voice-over script. It allows me as a researcher to focus on where he's going rather than trying to interpret what he's saying.
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Completed explanatory animation |
Transcript |
Researcher's commentary |
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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 than 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.
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In the voice-over script / imagery table he wrote during our last animation session his instructions to me for the percentage scene were: "0% -1%-2% up to 40% flashing fast over screen." I decided to start at 100% and work down to 40% instead as the point is that solar cells are not as efficient as we would like them to be.
The scene about silicon being very shiny shows a smooth and effective transition from a clear to a dark solar panel. This was simply done using a dissolve transition between a clear image and a dark one during the video editing process.
There was one final part that we simply deleted to keep the animation under 2 minutes. We were quite serious about including it as it seemed that this extra point allowed for a full explanation. He had even recorded it:
Another issue is that the electricity generated by a photovoltaic cell needs to travel through a semiconductor and semiconductors aren‘t great at conducting electricity. Wires are good conductors but they block out light so new transparent conductors are being developed to improve solar cell efficiency.
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Final director's commentary |
Transcript |
Researcher's commentary |
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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 than 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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It's funny that he says that the decision to amend his title from "Solar panels" to "Solar cell efficiency" was "half way through" the project. It was actually during session 15 which was 87.5% of the way through. He also thought the whole Storyboard project ran over one term when it was actually two.
The story he tells here about the stadium analogy with the empty seat and people (electrons) shuffling along came from the "Electron hole" entry on Wikipedia which uses this analogy to explain an electron hole being the conceptual and mathematical opposite of an electron. Animating the stadium analogy would have been straight forward but we decided that this would have been taking the atomic view too far for our purposes. This is why the decision was made to rename the topic to "Solar cell efficiency."
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Initial conceptual consolidation rubric |
Final conceptual consolidation rubric |
Researcher's commentary |
| Uses correct terminology |
With assistance |
Simplified terminology |
Some correct terminology |
Actual terminology |
Identifies relevant variables |
Not apparent |
With assistance |
Basic understanding |
Deep understanding |
| Identifies relationships between variables |
Not apparent |
With assistance |
Basic understanding |
Deep understanding |
| Self assessment. Does the student think that they understand their topic? |
No |
Not really |
Basic understanding |
Yes |
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| Uses correct terminology |
With assistance |
Simplified terminology |
Some correct terminology |
Actual terminology |
Identifies relevant variables |
Not apparent |
With assistance |
Basic understanding |
Deep understanding |
| Identifies relationships between variables |
Not apparent |
With assistance |
Basic understanding |
Deep understanding |
| Self assessment scale (1-10). Does the student think that they understand their topic? |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
8.5 |
9 |
10 |
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The 8.5 score for self assessment is what he said so I simply amended the rubric to accommodate a decimal.
I couldn't detect any major flaws in his ability to "identify relationships between the variables" but I wouldn't even give myself the "deep understanding" rating and it was me who finally realised what the problem was with the NP junction. Session 13 ended with both of us being unclear about which way the current flows. It turned out that this was from looking at the properties of the Negative (N) side and Positive (P) side separately rather than how they function when placed together in the NP junction. Together they create an electric field which is where the voltage comes from.
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This student has certainly come a long way from Session 4 when his initial attempts and an animation (see below) didn't explain anything about how solar cells worked:
Based on the mini case study provided by this student I'm developing the idea of an "implicit analogy." He alludes to this in his final director's commentary: "In real life the band gap energy doesn’t mean than 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." In this case the phrase "Band gap energy" changes size to reflect the fact the band gap energy (i.e. voltage) also changes. The actual change is a chemical one depending on the ratio of elements such as Boron in the P type and Phosphorus in the N type. "Implicit" is used in the general sense where it implies a relationship but actually refers to a different, chemical relationship. Boron and Phosphorus were mentioned in the voice-over script right up until the final version in week 16 when we decided that this would be better expressed as "silicon and other materials."