Author: phineas

General

Sankey Diagram Art

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Never thought that Sankey diagrams would inspire artwork, but here you go.

Whitey Flagg (check out the cool ASCII navigation on the front page, based on the NYC subway map!) uses satellite images, maps, info graphics, and the like as a model for his oil on canvas or acrylic paintings.

Here are some Sankey diagram artwork samples: The first is called “Energy Flow” (60.5” x 60”), the second “Water Flow” (42” x 75”), the last one “Carbon Emissions” (64” x 80”).

No. 1

energy_flow_Sankey_artwork

No. 2

water_flow_Sankey_artwork

No. 3

carbon_emissions_Sankey_artwork

All artwork is available for sale, so if you want to enjoy a real oil Sankey diagram, and have an appartment big enough to hang it, you can contact the artist. Also, check out the other paintings on his website.

Samples

Virginia Natural Gas Flow Sankey

The Virginia Center for Coal and Energy Research at Virgina Tech has a website on Virgina Energy Patterns and Trends (VETP).

This summary page on natural gas features a Sankey diagram for natural gas flows in Virginia in 2005.

VA_natural_gas_flowdiagram2005

Flows are in million cubic feet. Note that the division line between dry gas production (88.610 million cubic feet) and interstate imports (1.114.460 million cubic feet) overemphasizes VA’s own production. Also the magnitude of the “consumption” flow and “interstate exports” are not to scale, probably owed to the desire of the designer to be able to split up the consumption arrow into separate arrows. The transportation arrow is exaggerated, and would only be a thin line if to scale.

On the VETP summary page for coal, there is another interesting Sankey, also for 2005.

VA_coal_flowdiagram2005

The second one also has some pecularities: The Sankey arrows for imports (15.764 thousand short tons) and exports (21.288 thousand short tons) of coal are not to scale, neither are the losses/unaccounted coal flows 4.951 thousand short tons.

Reminder to self: If I find the time I’ll do these two diagrams properly and to scale.

General, Methodology

Sankey Diagrams are Directed Weighted Graphs

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For those of you interested in some of the maths behind drawing Sankey diagrams properly, you might want to read this article on ‘Programmatic Rendering of Directed, Weighted Graphs’ submitted for SVG Open 2003 by Philip A. Mansfield and Mark Ambachtsheer of SchemaSoft.

The authors consider Sankey diagrams as directed weighted graphs but they “can be difficult, time-consuming, and uninteresting to render by hand”. However, “Sankey diagrams do add an indisputable expressive power to a standard mathematical rendering of a graph…[and] when professionally constructed, Sankey diagrams represent flow in a manner … can be understood by anyone, instantly.”

Three diagrams are presented: the first is a simple directed, weighted graph representing a candy factory:

simple-weighted-graph

Next, a pen-sketched b/w Sankey diagram of the candy factory…

candyfactorysankeymanual

… and finally the corresponding Sankey diagram in SVG format, created using data in XML format and XSLT style sheet transformation.

svg_sankey_candyfactory

They also have some interesting details on graphical problems, such as overlay, edge layout, width of Sankey arrows in curves, etc. Basically all that stuff that developers of professional Sankey software tools have to cope with.

Samples

Showing Migration Flows as Sankey

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Most of the Sankey diagrams I come across on the net focus on energy issues, followed by the topics greenhouse gases and material flows of different kinds. Display of cost Sankey diagrams (value streams) is less common, so are people/passenger flows. An interesting approach is presented with Sankey diagrams that show migration flows between countries, or in and out of a region.

The best one I have seen was in this summary report on ‘Europe’s Demographic Future’ published by Berlin Institute for Population and Development. On page 11 you can see the migration flows within Europe (with omissions). The widest Sankey arrows are for migration movements from Bulgaria and Romania, mainly to Spain. There seems to be a lower cut off threshold at approx. 10.000, which leads to smaller flows not being scaled linearly any more. A lot of interesting details in this one… [would have loved to reproduce it, but permission wasn’t granted].

Here are other samples for Sankey diagrams visualizing migration flows (no quantities given, exact time range unknown).

Emigration flows to North and South America in the first half of the 20th century

emigration_flow

Refugee flows in Middle East, Africa and Asia in 2006 (clustered quantities)

refugee_flows

Both diagrams found on My Paris Your Paris blog

I think Sankey diagrams in this context merit more attention. Will be looking for more of these…

Samples

More National Energy Flow Diagrams

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A followup to my last post: This thread on ‘The Oil Drum: Europe’ features similar national energy flow diagrams for UK (2007), The Netherlands (2006) and Switzerland (2007).

For the UK these Sankey diagrams are published by BERR (Department for Business, Enterprise and Regulation). Historic charts back to 1974 can be found on their website.

energy_flow_chart_uk_2007_berr

UK Energy Flows 2007, by BERR, via The Oil Drum: Europe

A commentor to Chris Vernon’s original post added the Swiss version of this Sankey energy flow diagram originally published by Swiss Bundesamt für Energie (BFE):

gesamtenergiestatistik_ch07_p10small

These Sankey diagrams have some nice details, which a worth a mentioning: The UK diagram shows stock increases and decreases with circles. The size of the circle has no significance, but the magnitude of the in and out flows seem to be to scale, thus allowing to see if the stock has increased or decreased in that year. Losses at transformation steps are shown with “hanging arrows” (the flows branching off to the bottom line of the diagram). The Swiss version also shows exports this way, but visualizes losses with a pin with a big round head.

Even though your run the risk of being overwhelmed by a gloomy feeling when your read through the comments to Chris Vernon’ post, I would like to draw your attention to a comment by “realist” on Sept 5. He writes: “Deceptive graph! Why show losses for electric power generation and not transportation? The heat losses from the internal combustion engine in most transport is 70-80%”. This is true, but I have always understood that losses explicitly shown in these energy flow Sankey diagrams are the losses occuring in the energy generation, conversion and grid, while losses in the energy consumption (such as use for transport) are not shown. This let alone that they are worthwile to discuss.

Samples

Sankey for Energy Flows in Spain

3 Comments on Sankey for Energy Flows in Spain

One type of Sankey diagram layout seems to get popular recently. A representation of national energy flows of a country with the energy carriers on the left side (source), and the consumption sectors on the right side (sink). The Sankey flows in between show how energy from these sources are consumed and in which sector. Wasted energy is shown, and the overall energy (in)efficient use of primary energy is made clear with such a Sankey diagram.

I just discovered the energy flow diagram for Spain for 2006 on Joan Vila’s blog.

sankey-energia-espanya-2006

Unfortunately I don’t speak Catalán (well, I learned that “blog” is “bloc” in Catalán!), and the image quality isn’t very good. You can see nuclear, natural gas, coal (“carbó”) and crude oil (“petroll”), as well as hydro an wind (the two green lines) on the left side. The top box on the right side that takes the big red Sankey arrow for losses from electricity generation (“pérdues”). The others are the use sectors transport, industry, and domestic / services / agriculture. Vila calculates an efficiency of 38,2% for the electric power generation.

Joan advocates Sankey diagrams for visualizing and being able to better understand the issue. He says, that you won’t understand many things about what’s going on, if you don’t study this [kind of] diagram (“No entendrem moltes coses sobre el que passa si no estudiem aquest diagrama.”).

Check out simiular diagrams for Japan, Scotland, Ireland, Canada, United States.

Samples

“Sankeyware”

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Just back from a short late summer holiday, enjoying a few “Sankey-free” days at the coast. To get going again I am presenting a Sankey diagram you might have seen already. It is Gabor Doka’s sample diagram for his ‘Sankey Helper’ application.

Sankey diagram created with Sankey Helper 2.1 (by G.Doka)

The tool comes as a Microsoft Excel workbook, with a number of macros and a toolbar that allows to create shapes and assignments from the data sheet to these shapes. Of course, graphical layout capacities of this helper tool is limited, however, simple diagrams can be drawn easily once you understand how to handle it.

Sankey Helper 2.1 is freeware – err, sorry! – “Sankeyware”. You must sent the author a Sankey diagram you created, but otherwise there is no cost. Nice idea! Download Sankey Helper from Gabor Doka’s website.

Samples

COD loads in Wastewater Treatment Plant

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This Sankey diagram shows COD (chemical oxygen demand) in a waste water treatment plant that handles both municipal waste water as well as effluents from a chemical plant.

It was generated using the software package STOAT, which allows for dynamic simulation of wastewater treatment plants. Image with kind permission of Berlin-based EnviaTec GmbH.

stoat-model-sankey

The Sankey diagram does not show any flow quantities explicitly, and the values seem to be clustered into five or six fixed arrow magnitudes. The flows have a flat arrow base, and a rounded arrow head, which is uncommon, but still let’s you determine the flow direction. Process clipart icons overlay the nodes, where flows branch off or merge.

I have added the STOAT model to the list of software tools with Sankey drawing capabilities.