Sankey Diagrams

Found this Sankey diagram for UK energy flows in 2011 on reddit. Unit is TWh. Original source: ‘Digest of United Kingdom Energy Statistics 2012′.

While monochrome can be soothing for the eyes at times, this one definitely hurts my aesthetic sense: Too many shades of grey, arrows overlapping, pasted together from rectange it seems.

A colorful Sankey diagram for energy flows from Sweden. Found this one on the web page of Länsstyrelsen Skåne (please don’t ask me to read this out loud…) in an article titled ‘Skånska hushåll i fronten för mindre fossilberoende’

Unit of flows is TWh. The orange arrows are imports, the other arrows from the left apparently domestic production, with the majority of energy being from fossil fuels (“Fossilt”). Consuming sectors are at the bottom – in contrast to the typical layout of this kind of energy balance diagrams.

Anyone from Sweden who wishes to comment and explain a little bit?

Have you ever heard of the city of Issaquah, WA? To be honest, I hadn’t heard of it until I read this post on the New Energy Cities blog.

Issaquah is one of ‘New Energy Cities’ in the Northwest that has created an Energy Map and calculates the carbon emissions it is responsible for based on the fuels used. The role model for these Sankey diagrams are the ones published by the EIA.

Elizabeth, the author of the post, writes:

“Total carbon emissions are depicted in the gray flow lines, by both source and end use. The blue flow line represents hydropower energy used for electricity generation; the green represents non-hydropower renewable energy used for electricity generation; the brown represents nuclear energy used for electricity generation; and the red represents coal energy used for electricity generation. The orange flow lines represent natural gas used for electricity generation and direct heating. The pink flow line represents petroleum used for transportation. The dark gray flow lines represent electricity consumption by residential, commercial, and industrial user categories.”

Wow! I’ve seen those energy Sankey diagrams for the world, for nations and for federal states. But this one for Issaquah is definitely the one that covers the smallest geographical and administrative entity.

Came across this Sankey diagram showing the energy flows in Peru in an article on Renewable Energies in the Energy Strategy on Alberto Ríos Villacorta’s blog.

It has the typical structure of a national energy flow Sankey diagram as I have shown here on the blog many times. Flows are in terajoule (TJ) and have a general left-to-right orientation. On the left are the different energy carriers (primary energy), conversion in the middle section, consuming sectors on the right. Losses branch out to the bottom.

Unfortunately the streams are not to scale in this Sankey diagram. Compare for example the 80.149 TJ energy from “leña” (wood) in green to the 515.929 TJ of energy embodied in gas (sand color) right above. The gas arrow should be approximately 6 times wider – still it is drawn thinner. Even worse the situation for losses in gas processing where 241.007 TJ are “no aprovechada” while 274.922 TJ pass through gas processing (“planta de gas”). Roughly half of the energy embodied in gas is not used, but it looks as if that arrow branching out to the bottom represents some 10 to 15% of the total flow only. Many other examples of wron arrow magnitudes can be found.

So, some very general basics of Sankey diagrams are ignored here. Readers should check the flow quantities carefully, and not rely on the perceived quantities represented by the arrows.

A Sankey diagram made up from rectangles is shown in this post on the blog ’8-e.fr’ by MM.

The diagram is based on data for 2011 by the French national statistics bureau (INSEE) and the statistics observatory (SoES) of the Ministry for Environment and Sustainability. The author of the post comments that modifications were made in regard to the conversion of primary energy (“Nous corrigeons ce défaut de principe de l’INSEE pour mettre en relief les énergies primaires et secondaires réellement utilisées ou fournies.”) using average efficiency factors.

There are two sets of units: the black figures in MTEP (French for ‘million tons of oil equivalent’ MTOE) and the blue figures in MWh. Even though the flows are drawn with rectangles, one can grasp the general direction from top to bottom/top to left and losses to the bottom right by means of small arrows on the bands themselves. The width of flows seems to be pretty much to scale. The whole diagram a bit overloaded, with a high information density. Nevertheless, it caught my attention…

Found this Energy Flow Diagram for Bavaria (Germany) on the Bavarian Ministry of Economy website.

Flows are in Terajoule (TJ). Flows from top to bottom with different consuming sectors like private houdholds, traffic and industry. Different shades of green…

While I generally welcome the fact that these Sankey diagrams are published for nations, regions or states (as is the case here / more examples can be found here on the blog!), I find that care must be taken to respect the basic principles used for these diagrams.

In that respect the above example looks somewhat quirky to me. The reason for this diagram being spoiled is the fat stream (1.195.019 TJ “Umwandlungsverluste insgesamt” – not sure what that means though) merging into the vertical band from the left, and its counterpart (1.701.846 TJ “Umwandlungseinsatz insgesamt”) branching out to the right at more or less the same height. Are these additional inputs and outputs? But then, why do they cross the main direction of the flow? Not clear to me…

Not a good example. I would have expected better from the state where two of my favourite cars are manufactured.

The “personal” energy balance of the Grieger family home for 2010 and a forecast for 2012 were presented in two blog posts here and here on Klaus Grieger’s blog.

All consumptions are traced back to the primary energy demand and include losses (dark rey arrows) in power generation by using efficiency factors.

2010

2012 forecast

The details of these Sankey diagrams are probably most interesting for those who understand German.

A PV system on the roof of the Grieger house permitted to feed back 5930 KWh of electric energy to the grid in 2010. In 2012 some of this energy is used directly (“Eigenverbrauch”), leading to a reduced energy bill for electricity purchased. Note that the Grieger family gets “green power” from hydro, wind and other renewables.

Another change between 2010 and 2012 is an updated mix of energies German Rail use (nuclear, coal and gas fired power plants).

Note that the two diagrams do not have the same scale. The consumption of heat is the same in 2010 and the 2012 forecast, so is primary energy demand from natural gas (grey arrow “Erdgas” at the top). Still, the 2012 Sankey arrows are wider than in the 2010 version. It would be nice to have the two Sankey diagrams side-by-side and be able to compare them by looking at the arrows widths.

From a briefing document ‘Global and Canadian Context for Energy Demand Analysis – Energy Briefing Note’ (original source: ‘Powerful Connections: Priorities and Directions in Energy Science and Technology in Canada, Natural Resources Canada, 2006′) available on the National Energy Board website comes this Sankey diagram for Canadian Energy Flows in 2008:

Barely legible, but flow quantities are in Exajoule (EJ). The large bands that end about a quarter of the way are ‘exports’. Only the flows that go through to the power generation and consuming sectors represent domestic energy consumption.