## Combining Sankey Diagram and Pie Chart

Here is a good example of how Sankey diagram and pie chart are used side-by-side. In fact, the Sankey diagram picks up one particular piece of information that is already in the Sankey diagram.

This is from a German research report titled ‘Entwicklung eines EnergieReduzierten Verfahrens für den Erwärmungs- und Umformungsprozess von Parabel-Lenkerfedern durch Verkürzung der Verfahrenskette („EnRed“)’ published in 2010. [Note: no English abstract present, but title translates to sth like ‘Development of an energy-reduced process for heating and forming of…’ and from what I understand it is a hot rolling process]

It compares a conventional process with a new, energy reduced process. Here is the Sankey diagram for the conventional process and the pie chart right below.

The unit is kWh/kg, primary energy per kg of final product. The three colors are picked up again in the pie chart that shows the breakdown of primary energy lost in the provision of heat (brown, 12.3%) and in the ovens (red, 74.3%). Only 13.4% of the primary energy is actually used for heating of the rolled material (yellow).

Now, the pieces of the pie chart correspond to the widths of the brown, red and yellow output arrows as part of the primary energy input at the left. We are, however, typically much more used to percentages being represented in a pie chart.

A nice detail in the Sankey diagram is the split for the three ovens and the losses from the three ovens (red). The flows run in parallel and then are joined again at a bar that reminds me of a bridge, or the nut of a guitar … or the Brandenburg gate turned sideways as my nephew suggested 😉

## Spain’s Segura River Water System

This Sankey diagram for the water system of Segura river in Spain shows “the interchanged fluxes between the hydrological and the economical system”.

This is an output from the EU-funded ASSET (Accounting System for the SEgura river and Transfers) research project and can be found on the FutureWater website. Authored by Sergio Contreras and Johannes Hunink of Future Water (Contreras, S., J.E. Hunink. 2015. Water accounting at the basin scale: water use and supply (2000-2010) in the Segura River Basin using the SEEA framework. FutureWater Report 138).

Flows are for 2010 and measured in cubic hectometres (hm³, 1 hm³ = 1000000 m3 = 1 GL). The left part with the light blue backdrop is the actual hydric sector, while the right side with the light orange backdrop encompasses the technical/economic sector.

Water is extracted from surface waters (agua de superficie), ground water (acuiferos), and – interesting pespective – from soil water (água edáfica). Water from soil (green arrow, 901 hm³) is directly taken up by plants, so consumption is in the agricultural sector only. Agriculture is the largest consuming sector, followed by industry and energy generation, and water provision to households.

Much of the releases of water from industry and energy generation is returned to the water system (1734 hm³).

Additional tidbits of information below the Sankey diagram almost turn this into an infographic.

## Flow of Resources in Large Organizations

A group of people from Idaho’s Office of Performance Evaluations, an independent agency of the state, have contributed a post to the AEA365 blog – A Tip-a-Day by and for Evaluators back in June 2014.

Rakesh Mohan, Lance McCleve, Tony Grange, Bryon Welch, and Margaret Campbell recommend Sankey diagrams as “A Cool Tool for Explaining the Complex Flow of Resources in Large Organizations”

“Communicating the flow of dollars was the trickiest piece of the study. We considered narratives, tables, and traditional flowcharts. Ultimately, we used Sankey diagrams that helped stakeholders visualize funds moving through the department making them the most useful features of our report.”

The Sankey diagram depicted shows Idaho state funds in FY2013. Although the absolute figures or the total sum are not shown in this figure, the diagram is most likely based on real budget data.

## China Energy Flows 1971 and 2010

The article ‘Understanding China’s past and future energy demand: An exergy efﬁciency and decomposition analysis’ by Paul E. Brockway, Julia K. Steinberger, John R. Barrett, and Timothy J. Foxon (all of Sustainability Research Institute, School of Earth and Environment, University of Leeds, UK) appeared in Applied Energy 155:892-903 in October 2015 and features a comparison of China’s energy use in 1971 and 2010. These Sankey diagrams were drawn up to show “the overall ﬂow of exergy to end useful work, and the exergy losses that occur during the various conversion processes”.

China’s energy usage is roughly tenfold in 2010 compared to 40 years ago (37 Mtoe up to 355 Mtoe). Not sure whether both diagrams are setup on the same scale but judging from e.g. the black coal flow (140 Mtoe in 1971, 577 Mtoe in 2010) that is about 4 times wider, I would say they are.

Another interesting detail in these diagrams is that the authors have included food and feed as energy source. This is the first time I see this in a national energy flow map. Given that the energy content of this “fuel” is higher than both combustible renewables and renewables together, it seems justified to include it. The efficiency of turning food and feed energy into muscle work, however, is very low (approx. 3%).

I invite you to read the full article (open access) and to comment on the Sankey diagrams shown in Appendix B.

## University of Maryland, CHHP system

This Sankey diagram is from a presentation by a student team of University of Maryland. They participated in a Hydrogen Student Design Contest in 2011/2012 sponsored by the Department of Energy

The Sankey diagram is for a combined heat, hydrogen, and power (CHHP) system for the UoMD campus.

Flows don’t depict absolute values, but rather how the fuel input (municipal solid waste, organic waste, natural gas) is split into energy outputs (electricity, hydrogen, and steam). Losses (52.4%) at each process stage are shown as red arrows.

Drawing Sankey diagrams on a world map to show flows between different geographical location is always a challenge. One of the inherent problems is that large (=broad) arrows may run between two points on the map located very close to each other. Another problem is that one wishes to have the arrows more or less along the actual trade routes, which in many cases is close to impossible (take, for example, ships going through the Panama or the Suez canal).

I have shown quite a number of ‘Sankey diagram maps’ here on the blog, but most of them had shortcomings. Now here is an example that does extremely well in tackling the issue of Sankey diagram flows on a world map.

(CC licence – Carbon Brief)

This flow map of coal exports around the world shows the top exporters. It was crafted by Rosamund Pearce for the Carbon Brief article “Mapped: The global coal trade”. She decided to route the Sankey arrows nicely sorted, in parallel, and not along the actual shipping paths. See how much of the coal trade from Indonesia to China is led “virtually” south of Australia and New Zealand? Additionally the arrows are not led precisely to the actual port, but rather connect at a suitable place of each continent. With these simplifications the trade flow map is much clearer, understandable.

Another world coal flow diagram from 2012 can be found here.

## Lying with Sankey diagrams (6)

I really find it innovative when consulting firms show Sankey diagrams on their website to illustrate their work, and market their services.

However, I find it weird when these diagrams violate the basic rules of Sankey diagrams and flows are not proportional to the flow quantity. That doesn’t really contribute to build up confidence in their capabilities.

‘nough ranting … Have a nice weekend!

## Water Use in Qingdao, China

Interesting Sankey diagram on water use in Qingdao, China in 2011. This is from a presentation titled ‘Urban water security – Water-energy-food nexus’ by Josh Weinberg of Stockholm International Water Institute. Atkins and World Resources Institute (WRI) appear as co-authors.

Unit of flow seems to be million m³ （百万立方米）. Water origin is mainly surface water (455 mio m³) and local ground water (367 mio m³), with some additional (146 mio m³) brought in from Yellow River and Yangtze River.

Not sure about the split shown with two green flows, possibly breaking down the water use to urban (city of Qingdao) and province.

The middle part shows consumers: Farming (?) is largest consumer with 311 mio m³ per year, followed by ??? with 230 mio m³, and use in industry with 153 mio m³. Polluted water is shown in black.

Maybe someone who reads Chinese wants to chime in…