1. Energy Transfers 8 x £1 Coins Useful for the vending machine!
Comparing energy to money! I need some change for the vending machines.
10 Pound Note
8 x £1 Coins
1 x £2 Coin
Useful for the vending machine!
Doesn’t fit in the machine!
I use the analogy that I had to get change for the vending machine, but the only change given was 8x£1 and 1x£2. I still have £10, but it looks differently and some of it isn’t useful for the vending machine (the £2).

2. Energy Transfers Wasted Input Useful 10 Pound Note 1 x £2 Coin
A visual to show that they look different.
Wasted
Input
Useful
There is still 10 pounds available, but it now appears differently.

3. Sankey Diagrams
Introduce this as a representation of energy transfers, and explain that we will take a step by step approach for drawing a sankey diagram.

4. Sankey Diagrams
Step 1) start with a blank piece of graph paper.

5. Sankey Diagrams
The height of the box represents the amount of energy that is put in.
Step 2) Draw a box to represent the input energy. Emphasise that it doesn’t matter how long the box is.

6. Sankey Diagrams
The height of the next box represents the amount of useful energy.
Step 3) Draw a second box to represent the useful energy.

7. Sankey Diagrams
The height of the final box represents the amount of wasted energy.
Step 4) We draw another box to represent the wasted energy, however, we rotate it around to show it is wasted. I liken this to a toilet, our waste goes downwards.
But we rotate it to show that it is wasted energy.

8. Sankey Diagrams Useful Output Energy Input Energy
Finally we add arrows to our boxes and label the diagram.
Step 5) Complete the arrows and add labels.
Wasted Output Energy

9. Sankey Diagrams 8 x £1 Coins £ 10 Note 1 x £2 Coin
Show for the money example, asking students where they think the boxes should go.
1 x £2 Coin

10. Energy Transfers Light Energy 8 Joules Input Useful Wasted
Now for an example, an energy efficient light bulb.
Electrical Energy
10 Joules
Light
Energy
8 Joules
Heat Energy
2 Joules
Input
Useful
Wasted
Now compare with a real example.
There is still 10 joules of energy available, but it now appears differently.

11. What about energy? Light Energy Electrical Energy 8 joules 10 joules
An energy efficient light bulb with an input energy of 10 joules, useful output of 8 joules and a wasted output of 2 joules.
Again I asked students where they think the boxes should go.
Heat Energy
2 joules

12. What makes a good sankey?
Arrows are labeled with input and output energies.
Light Energy
8 joules
Electrical Energy
10 joules
Boxes are the correct width.
Straight lines, drawn with a ruler.
Emphasise what makes a good sankey and what you would expect from their work.
The wasted energy is labeled.
Heat Energy
2 joules

13. What is wrong?
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End
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Mistakes: no units, not drawn with a ruler, drawn in pen rather than pencil, incorrect title, if this was for a light bulb then the wasted energy is in the wrong place, arrow sizes are incorrect, labels are not fully completed.

14. Arrows are labeled with input and output energies.
Boxes are the correct width.
Straight lines, drawn with a ruler.
An example of a good sankey. Show this slide and emphasise that sankey diagrams don’t have to be coloured in. I would also leave this slide up whilst students work on their sankey diagrams, as a reference point.
The wasted energy is labeled.