Was browsing through my bookmarks and saved images and found the below diagram. Blame it on my mood today, but this one calls for bashing.

Published in a 2010 report by Australian Government, Department of Resources, Energy and Tourism. ‘Energy Efficiency Opportunities. Energy–Mass Balance: Transport’ figure 11 on page 26 this so-called Sankey diagram looks like a aerial view of my nephews playing room with his building blocks spread on the floor… While I generally appreciate a Sankey diagram being used in a government report on energy consumption or loss in transport, I think this one is poorly executed.

If you look at the numbers you will even see that they don’t add up correctly at the ‘Motive Power’ node.

The diagram shows how energy from fuel is lost in different stages of a vehicle motor (engine, power train, transmission) with approximately 21% of the energy being used as power at the wheels. This value is just an example, and not for one specific vehicle. But 20% efficiency seems to be more or less the average in a passenger car.

I remembered I had seen another Sankey diagram on the e!Sankey forum with the same topic.

This one is in German but you may be able to understand the main items. The red arrow are losses at the motor. The stacked turquoise-blue arrow to the right (18.5%) is energy-at-wheel. All in all there are many more details, but still the diagram remains rather “compact”.

I am sure there are more Sankey diagrams on energy losses in vehicles out there. Let me know if you find other examples to compare.

Found these two Sankey diagram on Wikiversity. I think it was somewhere on one of the sub-pages on the small solar vehicle… They show energy losses at the different components of the vehicle, such as at the solar panels or through rolling resistance. Percentage values.

These diagrams are made up from rectangles and simple arrows. Only straight arrows, no curves. The blue color of the border of some of the thinner arrows adds a strange effect…

The below Sankey diagram from the JS Systems homepage tries to show the differences between a normal Otto engine and the “JS Motor”. The prototype JS rotation motor, from what I grasp, has different compression and expansion parameters and could prove to be twice as efficient.

To show the difference in efficiency, two Sankey diagrams have been superimposed. The diagram with the grey outline is for the Otto engine, the one with the red outline is for the JS engine. The diagram shows energy losses branching off to the right (e.g. thermodynamic losses 17% in a typical Otto engine, 13% only in the JS motor). Useful energy is represented by the flow to the top.

I am not endorsing this motor, nor have I seen it work. But I like the idea of presenting a comparison in one Sankey diagram instead of two separate Sankey diagrams.

Also, please check out this previous blog post on Sankey diagram overlay.