Author: phineas

Energy Balance for California

California Energy Commission in 2005 published the final report of a project called CALEB (California Energy Balance). The CALEB database is compiled by the Lawrence Berkeley National Laboratory (Berkeley Lab) and contains “data for energy production, transformation, and consumption for the State of California for the period 1990 to present.”

The report shows the California energy balance for the year 2000 as a Sankey diagram. (Source: Murtishaw S, Price L, de la Rue du Can S, Masanet E, Worrell E, and Sathaye J, 2005. Development of Energy Balances for the State of California. Sacramento, CA: California Energy Commission CEC-500-2005-068 (LBNL-54923))

A PDF with this diagram explains how to read it:

Reading from left to right, the figure shows all the inputs of primary (and imported secondary) energy into California’s economy in 2000. These are summed by major fuel types in the middle of the figure: petroleum and associated products, natural gas, and inputs to electricity generation. The right-hand side shows how all of the fuels are allocated to the various end uses.

The executive summary explains that the diagram shows some peculiarities for ‘Arnieland’ compared to other states. It also points out that further research is needed to collect more data and to be able to break down aggregated energy data.

This way of presenting the energy balance seems to develop as a kind of standard for representing energy flows for a state or country. Other examples can be seen here: Japan, Scotland, U.S., or Sweden.

The diagram has two special features which distinguish it from other Sankey diagrams:

Firstly, it shows negative flows as dotted Sankey arrows, indicating “instances where consumption is greater than supply” – something which on a physical level is of course impossible, but is explained with statistical differences and “unexplained transformation gain … in petroleum refineries” (NB: I would prefer to read “data inconsistency” here).

Secondly the breakdown of primary energy and imported secondary energy (input from the left) is fanned out leaving gaps between the arrow lines. The merged arrows are then “condensed” to be to scale again. This creates a 45° gradient at one side of an arrow section (or “slope” for those of you who are into winter sports). In these sections the arrow width can not be proportional to the quantities. A tribute to pay for better legibility of the diagram.

Materials Accounting and Mass Balances

Environment Canada in 2001 published a Pollution Prevention Planning Handbook, a 153 page guidance manual on processes and techniques for pollution prevention. Update: The original handbook has been removed. Sucessor pages have been put online, and can be found here.

In appendix B of the handbook materials accounting and mass balances are presented as one technique. The text states that

materials accounting and materials mass balances can be presented in a tabular or diagrammatic format. A Sankey diagram provides one useful method for representing a picture of material flows and balances.

and a sample Sankey diagram is shown.

Although not all quantities of the individual flows are shown, and there is no reference to the unit used, I think this is a fine example of using Sankey diagrams. The mass imbalance at the first process “Presse” (at the very left) is clearly visible. From the neighboring downstream processes you can see that at least 2105 units (to “Trémie”) and 738 units (to “Évaporation”) leave the process, that has inputs of only 2616 units. The diagram was made with S.Draw.

Energy Sankey Diagram for Japan

Some of you might have noticed that I tend to get somewhat excited when I discover Sankey diagrams in other languages.

Here is one I dug out on this webpage of the Tsuji Labs at Osaka University in Japan, and it has the honor to be the first one presented on this blog in Japanese!

The diagram shows the “energy flows” (エネルギーフロー) as relative values for the year 1993 only. On the left side we can see that more than 80% of the energy consumed in Japan were produced from imported fuels (輸入), while only 17.8% came from domestic production (国内生産). The quantities are broken down into the different types of fuels, such as crude oil (原油, 46,1%) , natural gas (天然ガス, 10,5%) or hard coal (石炭, 16,4%). The right side of the diagram shows the consumption sectors, with industry (31%), residential (16,9%) and transport (15,6%).

Losses are at 29% which seems relatively low, if you compare to similar Sankey diagrams from the U.S. But then I am not sure if they accounted for the losses in the same way for this diagram.

There are these two other similar Sankey diagram thumbnails on that site, and my guess is that they represent different energy scenarios, considering renewable energy sources, as an option to reduce dependency from imports. Maybe someone who can read and understand more Japanese than I do wants to comment?

Biomass Utilization Potential

The first Sankey diagrams in Lao language I have come across are from a management summary on “Alternative Energy and Energy Conservation in ACMECS countries”. It shows how much biomass from wood industry, rice mills and other sources is available in the People’s Democratic Republic of Laos as rejects, and could potentially be used for generating energy. All values in tons per year for 2004 or 2005, extrapolated to the whole country from 4 to 6 samples.

Wood Industry: pink arrow is for sawdust, dark yellow arrow for woodbits, summing up to roughly 25%

Rice Mills: green arrow is for rice bran, yellow arrow for husks, summing up to 40%

Corncobs: orange arrow (20%) is corncob reject that could potentially be used for energy generation.

Even though I don’t read or write Thai, I love those letters. For those of you who wish to read the summary in English (with only 2 Sankey diagrams), a translation is available. Update Nov 2008: Unfortunately the website has gone offline

Greenhouse Effect Explained with Sankey Diagram

Doing a Google image search on ‘greenhouse effect’ brings up numerous versions of a diagram, that shows solar radiation partially being filtered by the atmosphere, partially hitting earth’s surface. This energy heats the earth, a part is being reflected as infrared radiation, where it is not able to escape fully due to greenhouse gas molecules from man-made emissions’ accumulated in the atmosphere.

While some of these greenhouse effect diagrams use simple arrows, some of them show the energy levels with Sankey-like arrows.

Wikipedia has one of these as an illustration for the article on the greenhouse effect. Originally designed for Global Warming Art it is also available in the Wikimedia Commons in Finnish and in Japanese.

Many of the “normal” diagrams are very appealing, and I especially like the one’s that target at kids or students. However, the diagram using Sankey arrows conveys more information. Check for yourself by comparing the two examples above.

Sankey Chart or Sankey Graph?

User ‘taqua’ at comments on another topic:

there is a fundamental difference between a *chart* and a *graph* or diagram.

A chart is a map of some data (like a city map, but for mass-data). It is a graphical visualization of tabular data. Charts are used for statistical purposes. Charts may be helpful to make mass data more understandable.

A graph is a graphical representation of a relationship between some objects or concepts. (In other words: A graph is a drawing that explains how something works or behaves.)

It is a common property of human languages, that terms get mixed, so you will find the word ‘chart’ in classical graph types, like ‘flow-chart’. Nonetheless, by sticking to the definitions above, it is easy to see that a flowchart is no chart at all – its a graph.

Taking this into consideration, a Sankey diagram can be considered both, a Sankey chart and a Sankey diagram. The quantities represented by the magnitude of the flow could also be shown as tabular data, the direction of the flow, given by the arrow orientation between two processes indicates a ‘from-to’-relationship.