This website on energy optimized building features a case study of a students dorm building at Wuppertal, Germany. [On a side note: it is quite striking that when I browse for new Sankey diagrams on the web, I come across them on German websites. Herr Sankey could well have been a German…]
The two Sankey diagrams shown along with the article visualize the heat energy flows before and after the optimization measures taken.
Flows are in kWh per square metre per year. The first diagram breaks down heat consumption into heat used for room heating and for warm water preparation. In the second a new heating system has been installed providing heat mostly over the air circulation system. Only some static radiators remain. [Thanks Thomas for helping me with the translation/explanation].
Apart from the use of a fancy color, the Sankey diagrams are well done and comprehensible. Flows are to scale.