The U.S. Department of Energy (DOE), Office of Energy Efficiency & Renewable Energy publishes Sankey diagrams on non process energy on this webiste.

What is non-process energy you might ask. According to DOE, non process energy is “energy used for purposes other than converting raw material into manufactured product. MECS-specified categories of nonprocess energy include facility HVAC, facility lighting, onsite transportation, other facility support (e.g., cooking, water heating), and other nonprocess use.”

You can access the energy flow Sankey diagram for the full U.S. manufacturing sector. Data is from 2010 and flows are in TBtu (Trillion British Thermal Units) per year.

Detailed diagrams on on-site generation, process energy and non-process energy (the three ‘transforming nodes’ in the middle of the full sector) are also presented.

Grey and black arrows show losses. Good work from the Office of Energy Efficiency & Renewable Energy.

Found this photo somewhere on my hard disk. Probably stored it from Twitpic…

This Sankey diagram is from a physics exam. Not sure whether Cornelius is the student or the teacher?!

Promise to get back to serious by the next post.

I found the below Sankey diagram depicting Romania’s energy flows for 2008 in an article titled ‘A Macro-Micro Perspective on Sustainable Refurbishment of the Housing Sector’ by Ovidiu-Horaţiu Teleche, University of Architecture and Urbanism, Bucharest. Published in Proceedings of 1st International Conference on Architecture & Urban Design, Department of Architecture (2012).

Flows are in ktoe (kilotons of oil-equivalents). Underlying data is from the Romanian National Institute of Statistics and Eurostat 2010. EPP is for ‘Electrical Power Plant’, CHP for ‘Combined Heat & Power Plant’, and DHP for ‘District Heating Plant’.
Note the small flow quantities where arrows are not to scale to be able to view them at all (minimum line width set to 1 or 2 px).

Energy generation is predominantly fossil (coal, petroleum, natural gas). Biomass is the most important energy source in the residential sector. The article doesn’t mention the reason, but my guess is on wood or peat “for preparation of hot water, cooking and direct burning in the stoves for heating” as mentioned in this article on biomass in Romania.

Another quick casual Friday post … again from Austrian company pro-wel, published on their website to market their process engineering services.

Enjoy your weekend!

This is what many have been waiting for, I think. The first Sankey app for iOS.

I have not tested it myself, since I don’t use iOS. But in the video on the Squishlogic website it looks fancy and moving around the nodes seems smooth. In the video they don’t show how arrows are drawn and flow quantitites are entered, but maybe Steve (who pointed out that new tool me) will comment.

Added to the Sankey diagram software list.

Interesting blog post by Steve Wexler of Data Revelations. Long article, long title: “Circles, Labels, Colors, Legends, and Sankey Diagrams – Ask These Three Questions”.

The really interesting part for the Sankey diagram aficionados is Steve’s advice on when to use Sankey diagrams, and when you should avoid using them.

Steve illustrates his point with the below example by ‘Music Major – Data Miner’ Jeffrey A. Shaffer (original post is here)

A combination of a stacked bar chart with a distribution diagram, nicely decorated with a trumpet … “Within this context, this very creative chart works”, Steve writes.

He then goes on and shows another one by Shaffer, also a distribution diagram: the original pie chart data from an energy bill has been redesigned and was presented as a distribution diagram (two stacked bars with bands to link them)

In this case, Steve concludes, the choice of a Sankey diagram is maybe not that wise, since the actual important information (44% of energy cost is for heating) doesn’t really come across quickly and clearly. A bar chart might work better here. Sankey diagrams can create a “cool!” or a “crap!” response, depending on the context. See the original Shaffer post here.

Adding my 2c from a technical perspective I would say that both diagrams have a shortcoming: The bands don’t maintain their width as they cross over the others diagonally. Somewhat acceptable in the trumpet diagram as the right bar on the right side listing the music composers is higher than the one at trumpet bell (sound spreading out). Not acceptable in the second diagram where the two stacked bars have the same height. This is obviously an error in the curve radius calculation (read ‘The Math Behind those Curves’)

Austrian technical consulting firm pro-wel offers process engineering services to its customers. Their website features two Sankey diagrams, one of which is a rare circular one with curved arrows (see others).

I also like the technical frame around the diagram, a must have in engineering and architecture.

I really liked Will Stahl-Timmins’ article on how he developed an infographic on energy consumption in a city.

Will’s blog is called ‘Seeing is Believing’ and his central claim is that information graphics are “the visual transformation of data into understanding”. I agree: infographics are more than just a diagram and labels. They are much more “visual” and their design elements add to a better understanding. Diagrams convey data, infographics convey information. Typically they also have a broader audience: you would find a diagram in a scientific paper, but an infographic in a daily newspaper.

The article ‘Visualising city energy policies’ gives a very good insight into the reasoning of an infographer/designer when creating an infographic. Will describes how he started out from an ordinary Sankey diagram, to get to an infographic step-by-step. This involved studies of different alternatives, sketches on paper, discussions with colleagues, presentations, and many different versions of the infographic in Illustrator…

He experimented with an isometric or what he calls a “pseudo-3D” perspective, but also discovered some shortcomings in using them.

Crossing arrows were an issue. So were the stacked nodes (cubes) that hid parts of flows and were difficult to label.

The “intermediate” outcome of his meticulous work was the below infographic. It seemed to have been a long learning process to achieve this result.

Will went on to include feedback he had gotten from fellow researchers, and decided to add more information on imported energy. At the same time he had to reduce the level of detail. This is the final infographic.

Good work, I think! The resulting infographic is not a genuine Sankey diagram anymore. There are only three arrow widths left, quantities are clustered in these groups. But as I said, an infographic has a different purpose.

It is not mentioned clearly how this infographic will finally be used, and who the target audience is. I imagine it will be used as an illustration in a brochure that summarizes the findings of the URGENCHE project, but to a wider, non-technical audience.

Make sure you read the full blog post at ‘Seeing is Believing’.