Stuttgart City Energy Flows

The energy balance of the German city of Stuttgart has been mapped as a Sankey diagram.

This was part of the project ‘SEE Stuttgart’ (City with Energy Efficiency / “Stadt mit Energie-Effizienz”) and has been developed by Fraunhofer IBP research institute.

A vertical layout was chosen. Absolute energy flow quantities are not shown in this version of the diagram, but are available in the underlying study. In 2010 primary energy consumption in Stuttgart was 20.300 GWh.

The diagram is used to promote a better understanding of the consuming sectors in the city, and the types of energy used. The SEE project aims to reduce Stuttgart’s energy consumption by 20% in 10 years and to transition to non-fossil fuels.

Stuttgart has actually won a first prize in a competition for energy efficient cities in 2016. It is thus setting a benchmark for other German cities. The above Sankey diagram is featured in this promotional video (in German) [at 2:36] and also briefly in this video (in German) [at 0:48] by IBP Fraunhofer.

A high resolution version of the Sankey diagram can be found here.

UK Electricity Generation Efficiency 2012

UK-based consulting firm Green Peninsula has the following Sankey diagram on their website showing electricity generation in the United Kingdom in 2012.


“In 2012 around 920 TWh of primary energy … went into electricity generation in the UK. Due to conversion [in]efficiencies during electricity generation and losses during its transmission, 65% of this energy was lost – primarily as heat. With around 320 TWh reaching the end user, this equates to an overall supply efficiency of around 35%.”

US Trade Flows, yet another option

After showing two variants for visualizing the U.S trade balance in my last post, I got aware of yet another option. The first figure (infographic by Spiegel Online) used the length of the arrows to express the value of imported and exported goods. My remake version used the magitude (width) of the arrows, as is typical for Sankey diagrams.

In this figure (by Anthony Cohen, University of Illinois, 2012 / Wikicommons) for US trade in 2011 the arrows for import (red) and export (green) are proportional to the total value of goods, just as we are used to see it in a Sankey diagram. But the arrows are superimposed, with the narrower green export arrow on top of the wider red import arrow. This creates another, somewhat more dramatic impression.

Data shown is for 2011 in billion USD for the 15 most important trade partners. Arrows are not labeled with absolute figures, instead a legend at the bottom indicates the width of five default arrows. The arrow from and to Mexico is a problem (no joke intended!), but the legend clarifies that arrows don’t indicate a specific geographic routing.

US Trade Balance, two versions

When German Chancellor Angela Merkel meets with POTUS today, one topic that’s most likely going to be addressed is the trade deficit between the United States and the EU, Germany in particular.

The Spiegel, a major German news outlet, has illustrated recent articles on this subject with the figure below. It shows the volume of trade between the United States and ‘selected countries’ (China, Canada, Mexico and the EU) in 2015. The values indicate the value of goods exported (green arrows) to these countries, and imported (blue) from them into the U.S. in billion US$.


Source: Spiegel Online

The interesting thing in this infographic is that the length of the arrows represents the value of goods traded. For example, the arrow for exports from the US to Europe (274 bnUS$ in 2015) is little over half the length of the blue incoming arrow (431 bnUS$ in 2015). This works fine, with the only exception being the green arrow for exports to Mexico.

This infographic of course invited a remake as Sankey diagram. As you all know, in Sankey diagrams the widths of the arrows represent the quantity.

I did two or three different versions, all very similar to the original infographic in style and color, even using the lower states map icon (sorry Alaska and Hawaii). I was not sure at first whether the separate arrows for Germany were values already included in the EU trade volume, or if they were meant to be on top of it. A quick look into the original data revealed that indeed they are included in the EU figures already. I therefore decided to highlight the German share in the Sankey diagram with a slightly brighter color, but keep those arrows stacked.

Here is my Sankey diagram version of the Spiegel infographic.

Not sure which version I prefer, but using the length instead the widths of the arrows to represent the flow quantity is definitely a unique approach. Worth sharing with you, I think.

Misc Sankey Diagrams Uncommented 14

Digging through some long untouched folders on my hard disk, I found this schematic Sankey diagram of iron and steel flows.


Schematic? Well, no quantities or units given, no time reference, no source of data. And no idea as to who the author is. Just take it as another miscellaneous Sankey diagram.

World Energy Flows in 1937

The below Sankey diagram from 1949 depicting world’s energy flows in 1937 is shown in this blog post by Michael Hohmann | LMH Design.


Flows are in TWh.
Michael says: “When I first saw this, I was reminded of seeing an octopus and called it an Octopus Diagram, with the octopus’ head at the input end at left, and the tentacles on the right, in between digesting and distributing everything that the various mouths at the head can gobble up”, asking himself “[w]here does all this Input energy disappear to with so little Output energy ending up as useful for us humans?”.