The Sankey diagram is in German and from the quality of the image I assume it is a scan from a printed publication. This seems to be a comparison of power plant technologies (‘Kondensationskraftwerk’ vs. ‘Heizkraftwerk’). The plant on the left has 63% losses and produces only electric energy, while the one on the right makes use of 88% (of the primary energy?) and produces both heat and electricity. A nice detail is the power plant silhouette sitting at the top.
If anybody has a clue where this vintage-style Sankey diagram has been originally published, please let me know.