The Energy Education References Wiki has a page on Sankey diagrams. It features many samples, snippets and links directed at teachers.

One image in particular caught my attention. This is described as “Energy Display System” created by CSIS in the 70s


(via Energy Education References Wiki)

You all know those national energy flow Sankey diagrams I show here regularly? Now imagine the same type of image as a series consecutive frames for several years. This would produce a kind of animated gif or movie showing changes over time.

The above must be an early 3D version of this. The diagrams are mounted on what seems to be acrylic glass…

In 2008, the Cartographia blog started a post series called ‘Monday’s with Minard’. Some people consider Charles Joseph Minard the first to use arrow magnitude in his diagrams to represent quantities. (As a consequence, this means that Sankey diagrams would have to be renamed to Minard diagrams!).

What differentiates Minard maps from Sankey diagrams is that Minard’s fine works always have a geographical relation. The most famous one is his Map of Napoleon’s march to Moscow published in 1869. This “carte figurative des pertes successives en hommes de l’Armée Francaise dans la campagne de Russie 1812-13″ shows number of men (as width of arrows), geographic movement of the troops on the map both for invasion as well as for retreat, as well as time and temperature on a separate scale.

Cartographia blog has some other nice examples, two of which are shown here:

The first shows migration patterns across the globe. Arrows do not have an arrow head but the country of emigration is color coded. The outline of the countries is distorted to accomoadate large flows connected to them. For a detailed description please consider reading the original blog post. This map is similar to the one I showed in this post.

The other is a flow map for wool and cotton for the years 1858 and 1861. “Blue represents cotton and wool from the United States, the orange from British territories in South Asia … One millimeter represents 5,000 tons of cotton or wool.”. As one can see on the 1861 map, cotton imports from Asia have increased dramatically. See the description of the map in the blog post on Cartographia blog.

See all Monday’s with Minard posts here. There has been no activity on the blog since June 2008. I hope to see more of these posts some day.

A scan of one of the first – if not THE first ever – published Sankey diagrams has now been added to the Dutch and German Wikipedia articles. Actually I had always wanted to get hold of a digital version of this this energy efficiency diagram published by Captain Henry R. Sankey in 1898 in the Minutes of Proceedings of The Institution of Civil Engineers. Vol. CXXXIV, Session 1897-98. Part IV.

First Sankey diagram published 1898 in JIE (Source: Wiki Commons)

Click here to see the image in original size.

Sankey used this novel type of diagram to represent energy flows and energy losses in a steam engine, comparing it to an ideal steam engine.

I do acknowledge that the term ‘Sankey diagram’ is not as common as a ‘pie chart’, and that many people don’t know it, even if they have a rough idea of this type of diagram. One might just call a Sankey diagram a ‘mass flow diagrams’ or ‘flow chart’, or ‘energy efficiency chart’. Or a ‘heat loss diagram’, as I have seen it once.

So, then: what is Sankey?

In times where “to google” is synonymously used for “to search”, a visit to Google will give you a first idea. I also recommend a query at Googlism, a site that has some very subtle answers to the above question (I very much like “Sankey is 7 or 7″ and “Sankey is aboard” ;) )

But seriously: Sankey is originally both a name of a locality in England, as well as a family name. Famous Sankey’s include Ira D. Sankey, a gospel singer and composer (1840-1908) and magician Jay Sankey. And of course the lesser known Captain H.R. Sankey, the first to publish an energy efficiency chart, and the reason why we call Sankey diagrams Sankey diagrams. I will try to aggregate some information on this personality, to honor his invention.