Category: General

Sankey Diagram Art

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

No. 2

No. 3

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.

Sankey Diagrams are Directed Weighted Graphs

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:

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

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

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.

The man behind Sankey diagrams @ LLNL

The Council on Competitiveness has just called on the presidential candidates to come up with a national energy plan, believing that future economic growth and security of the United States depends on energy efficiency across the U.S. economy, sustainable energy solutions, and development of new technologies.

The new president might want to ask John Ziagos to advise him on energy issues. Ziagos is with the Energy & Environment Directorate at Lawrence Livermore National Laboratories, and an expert for energy scenarios. For me as a Sankey aficionado he is simply the “man behind the Sankey diagrams at LLNL”.

LLNL has been publishing energy flow diagrams for the U.S. over the last few years. In his public presentations (link1 – 2.9 MB, link2 – 4.8 MB) Ziagos impressively shows that even when implementing fuel cell technology for all vehicles, switching completely from coal and natural gas to renewable energy sources to generate the nation’s electricity, and building 270 new nuclear power plants … even then it would not be possible to stabilize U.S. carbon emissions between now and 2050. “If we want to move toward a carbonless future, no single technology will do – everything counts.” Ziagos says.

I am reproducing two energy flow diagrams for the U.S. from John’s presentations below. The first is for 1976…

… the second a 2025 projection:

While overall energy produced will rise from 72 Quads in 1976 to an estimated 133 Quads p.a. in 2025 [Note: 1 Quad(rillion) equal to 10E15 BTU, or 1.055 × 10E18 joules (1.055 exajoules or EJ) in SI units.], the ratio of useful energy to rejected energy gets worse.

New version of e!Sankey

Good news upon my return from a summer break: e!Sankey 2.0 has been released by German software maker ifu Hamburg on July 15. I had participated in their beta testing in June, so I was well aware of what they would present…

The new version comes in two different flavours: a standard version and a “pro” version, which differs from the standard version by offering a ‘LiveLink’ for Excel files and material stocks visualization.

A full list of new features has been published in their BBS. Some are nice to have, such as the 40+ fill patterns or background colour for the diagram. Others are off real added value (at least in my eyes), such as rotating of labels, or padding at processes.



The implementation of the interface to Microsoft Excel (so-called LiveLink) is a big push and definitely justifies the price difference of 60 Euro (110 US$) for the e!Sankey 2.0 pro version. You can copy & paste values from Excel into the quantity field for a flow, establishing a dynamic reference to the cell in the background (cells should be named, so that their postion can be changed without losing the reference to the e!Sankey diagram). If the value in the Excel file is changed, the flow quantity is automatically updated, and the diagram adapted accordingly. Read more about the Excel LiveLink.

A 30-day trial version can be downloaded here.

I will play around with e!Sankey 2.0 pro (after I have dug through my inbox 🙁 ) and present some more Sankey diagrams within the next days…

Software Development Bugs Breakdown

This is an interesting one: Saveen Reddy shows a Sankey diagram-like breakdown of bugs in a software development project. The term ‘bug’ is used “…very generically to describe any issue being tracked, not only defects in source code.”.

This does not fully classify as a Sankey diagram, I think, because the arrows don’t seem to reflect any quantities (number of bugs, time spent on bugs, …). But just like the diagram that showed the number of people having been accused and the turnout of the cases I showed here in June 2007, it visualizes a sequence of breakdowns, leading to decisions that are taken (dashed line arrows).

Now, anybody wants to check their bug tracking tool and show a similar diagram but with real numbers?

A hand-drawn goodie

Browsing for more Sankey diagram goodies the other day I was delighted to find the following sketch in a brochure ‘Let’s learn about energy: a practical handbook for teachers’ published by the TACIS technical dissemination project.

The diagram illustrates a list of suggested activities for students, to teach them “why energy is important”:

Get students to draw up Sankey diagram (Figure 3) showing the energy flows through a process or activity. Consider a power station, house or car. The width of the arrows represents the amount of energy. Energy inputs (fuels, electricity) usually flow into the process from the left and useful energy outputs (heating lighting mechanical power, chemical energy) and losses (heat, noise etc.) flow out to the right.

And another language for my collection of Sankey definitions

Software: Energy Flow Sankey for Private Homes

A software with a Sankey diagram feature that I hadn’t noticed before, and only now have added to the list of Sankey Software tools is CASAnova (new house). From what I understand this freeware tool was the result of a research project at a German university that ran from 2000 to 2002.

The program ‘CASAnova – An Educational Software for Energy and Heating Demand, Solar Heat Gains and Overheating Risk in Buildings’ is designed for an easy-to-use handling in order to get an intuitive understanding of the relations between building geometry, orientation, thermal insulation, glazing, solar heat gains, heat energy demand, heating and primary energy as well as overheating in summer.

CASAnova can be used to enter numerous parameters for a building, such as geometry, window and wall areas and types, insulation, heating system, and climate data etc. The tool will eventually produce a generic Sankey diagram of energy flows as the one above. I have just installed it and played around a little bit only to get an impression. CASAnova is available in German and English. Recommended.

sankey-diagrams.com now on WP 2.5

I have updated from WordPress 2.3.3 to the long-awaited version 2.5. While the visitors of the blog might not even notice any difference, the management of the blog via the admin dashboard looks much more comfortable and cleaner to me. I have already played with the improved tags (tags are also visible in the footer of each post again), but still have to experiment with the new built-in galleries. Kudos to the guys at WP, you’ve done a good job. And thanks King Louie for helping me with the update!

Just for fun – here’s my Sankey-diagram-like schematic display of the upgrade to WP 2.5. The magnitude of the arrows this time do NOT represent anything (neither lines of code nor the amount of satisfaction with each feature….)