Another Sankey diagram type I have come across several times are the very compact ‘block-type’ Sankey diagrams. They basically consist of stacked rectangles, like in the below example from Wikiversity dealing with a solar vehicle project. A left-to-right flow orientation is indicated by the arrow heads peeking out of the stack on the right side.
The diagram shows a breakdown or use of the 100% (31.75W) of solar energy (‘globale straling’). The percentage values always refer to the previous block. This one also has a nice color gradient.