Sankey Diagrams

A followup to my last post: This thread on ‘The Oil Drum: Europe’ features similar national energy flow diagrams for UK (2007), The Netherlands (2006) and Switzerland (2007).

For the UK these Sankey diagrams are published by BERR (Department for Business, Enterprise and Regulation). Historic charts back to 1974 can be found on their website.

A commentor to Chirs Vernon’s original post added the Swiss version of this Sankey energy flow diagram:

These Sankey diagrams have some nice details, which a worth a mentioning: The UK diagram shows stock increases and decreases with circles. The size of the circle has no significance, but the magnitude of the in and out flows seem to be to scale, thus allowing to see if the stock has increased or decreased in that year. Losses at transformation steps are shown with “hanging arrows” (the flows branching off to the bottom line of the diagram). The Swiss version also shows exports this way, but visualizes losses with a pin with a big round head.

Even though your run the risk of being overwhelmed by a gloomy feeling when your read through the comments to Chris Vernon’ post, I would like to draw your attention to a comment by “realist” on Sept 5. He writes: “Deceptive graph! Why show losses for electric power generation and not transportation? The heat losses from the internal combustion engine in most transport is 70-80%”. This is true, but I have always understood that losses explicitly shown in these energy flow Sankey diagrams are the losses occuring in the energy generation, conversion and grid, while losses in the energy consumption (such as use for transport) are not shown. This let alone that they are worthwile to discuss.

One type of Sankey diagram layout seems to get popular recently. A representation of national energy flows of a country with the energy carriers on the left side (source), and the consumption sectors on the right side (sink). The Sankey flows in between show how energy from these sources are consumed and in which sector. Wasted energy is shown, and the overall energy (in)efficient use of primary energy is made clear with such a Sankey diagram.

I just discovered the energy flow diagram for Spain for 2006 on Joan Vila’s blog.

Unfortunately I don’t speak Catalán (well, I learned that “blog” is “bloc” in Catalán!), and the image quality isn’t very good. You can see nuclear, natural gas, coal (”carbó”) and crude oil (”petroll”), as well as hydro an wind (the two green lines) on the left side. The top box on the right side that takes the big red Sankey arrow for losses from electricity generation (”pérdues”). The others are the use sectors transport, industry, and domestic / services / agriculture. Vila calculates an efficiency of 38,2% for the electric power generation.

Joan advocates Sankey diagrams for visualizing and being able to better understand the issue. He says, that you won’t understand many things about what’s going on, if you don’t study this [kind of] diagram (”No entendrem moltes coses sobre el que passa si no estudiem aquest diagrama.”).

Check out simiular diagrams for Japan, Scotland, Ireland, Canada, United States.

A presentation titled ‘La eficiencia energética: una opción estratégica para la empresa y para el país’ (’Energy Efficiency - a strategic option for companies and for the country’) by Pedro Maldonado of the Energy Research Program (Programa de Estudos e Investigación de Energía) at Universidad de Chile features a Sankey diagram as an important tool in energy auditing.

The diagram shows exemplary losses (pérdidas) in heat generation, heat transmission and the use of heat. Use of heat is broken down into drying, pasteurization, evaporation, etc. The main message of the author: “The energy we purchase is not what we ultimately use as energy for our productive processes”.

A reminiscence to the days when Sankey diagrams were drawn in black&white by hand and labeled with a typewriter. The three Sankey diagrams below from a 1990 article on “Energy conservation in the mechanical forest industries” by FAO (Food and Agriculture Organization of the United Nations, FAO Forestry Paper No. 93, Rome 1990) illustrates energy use in sawn timber, plywood and particleboard production.

The article explains that

“Although the diagrams are of an approximate nature they do serve to identify the relationship that each major energy consuming centre has with each other and also readily identifies the prime energy users to which particular attention should be paid in any conservation effort.

In all three product manufacturing processes heating is by far the largest user of energy, representing some 82-87 percent of the total energy requirement in the manufacture of sawntimber, plywood and particleboard, with drying accounting for approximately 87 percent, 61 percent and 62 percent respectively.”

Use of Sankey diagrams with kind permission of FAO

The Council on Cempetitieveness 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 reprodrucing 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.

Statistics Canada in its “Report on Energy Supply-demand in Canada” for 2005 shows two Sankey diagram in the annex (HTML version of the two Sankey diagrams). They show the energy flows for Canada 2005 and 2004 in Petajoules per year.

I have featured similarly structured diagram for other countries here before: Japan, Scotland, Ireland, and the United States.

Out of 21380 PJ of total energy produced in Canada and imported, some 9641 PJ (45%) are exported, while 11739 PJ (55%) are national consumption. If you have the impression that the proportions are not 45:55, you are right, they are more like 39:61! From a graphical perspective this Sankey has more peculiarities worth a mention: the magnitude of the Sankey arrow changes and just before the arrow head they become narrower. The flows labeled “Steam” and “Adjustments” seem to have been added at a later stage as they don’t merge into the other arrow. Steam is represented on the production side as well as in the breakdown of energy carriers with a small, but not unsignificant width, however the quanity is given as zero.

This diagram of sun radiation being absorbed and reflected when hitting earth (from Solar Energy Facts website) is a rather weak remake of the original Nasa diagram.

I find the floating powerpointish arrows kind of disturbing, and with the arrow magnitudes not to scale, would even call it misleading. Took the time to prepare two new versions of it (actually I am beta testing the new version 2.0 of e!Sankey at the moment - so this was a nice little test case).

The first version sticks more to the original idea of the diagram shown above, but the arrow magnitudes are corrected and to scale. The second version is closer to the original ‘Breakdown of the incoming Solar Energy’ diagram by User A1 that can be found on Wikicommons. The latter one has the flow for energy being absorbed by atmosphere (33 PW) branching off as the first arrow horizontally.

ENOVA is a public enterprise owned by the Royal Norwegian Ministry of Petroleum and Energy. It advises the ministry in questions relating to energy efficiency and new renewable energy.

One of their services is the practical development of energy and climate plans (Kommunal energi- og klimaplanlegging) for Norwegian municipalities. On their website they present a sample Sankey diagram to visualize energy flows.

The Sankey diagram shows the energy flows in the Stor-Elvdal municipality in GWh (probably per year, a year is not given). This is very interesting, as the municipality can cover almost all of its energy for industry and private households from renewable energy sources, such as biomass and wind. Energy from fossil sources is consumed through almost entirely transportation. Stor-Elvdal produces 47.5 GWh within the municipality, and imports another 35,8 GWh from wind from outside the municipality.

A small typo can be found in label on the the orange flow (saying 85,8 where it should read 95,8), but this doesn’t spoil the overall quality of this diagram painted with SDraw, I guess.

Download the publication (in Norwegian) as PDF file