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 http://www.dede-acmecs.com 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 jfree.org 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.

Cost Sankey Diagrams show Added Value

While browsing through some of my older bookmarks I discovered this page of what seems to be an information portal of one of a German federal ministry. The Sankey diagram for cost flows they show reminded me of a feature in the Umberto material flow management software, which I always wanted to inspect in more detail.

Using their 30-day trial version I worked with one of the simple demo examples they provide. Basically this software is a modeling tool for process systems and analysis of material flows within any kind of process system (production plant, supply chain, region, …). Sankey diagrams in Umberto are not the default view for material flows, but one can switch from the normal “Material Flow Network” view to the Sankey view.

Even though the Sankey diagram feature of the software would need some retouching, I was surprised and extremely pleased to see a “Cost Sankey” feature.

You can enter material direct cost for all materials (in the ‘bucket factory’ example of the demo all materials already have a “market price” property), as well as fixed and variable process costs. The variable process costs are spread over the process throughput using ‘machine hours’ or ‘work hours’ as cost drivers (i.e. to link cost creation to the material throughput). Thus, at every process (shown with blue squares in the flow diagram) the costs -or should I say: the value – increases. Going from left to right along the general flow direction in the Sankey diagram you can see clearly that the growing magnitude of the Sankey cost flows… a kind of ‘Value Added Sankey diagram’.




The above screenshots show the overall cost for the three products produced in the bucket factory (Fig.1), the cost per unit for each of the three products of the bucket factory (Fig.2).

The following two cost flow Sankey diagrams are for the individual costing units ‘plastic bucket’ and ‘watering can’ (Fig.3 and 4). Please note that on theses diagrams a part of the machines is not being used, so they don’t add any process costs to the costing unit (or don’t contribute to the value added). Unfortunately you can only display either mass or energy flows in one Sankey diagram, so the energy costs (from the circle labeled ‘other materials’) are not shown as a Sankey flow, even though they add to the price for each product.

Incoming and outgoing cargo @ Rotterdam Port

Last weekend I had the possibility to visit a friend in the Netherlands, and we took a tour of Rotterdam Port. Despite the bad weather, I was fascinated by the huge container ships, the cranes, the noises….

Back home I did some research and came up with the cargo data for the year 2005 from the Port of Rotterdam website.

I did the following three Sankey diagrams. The first shows the inbound cargo quantities (in million tons gross weight of cargo) from the left, and the outbound quantities to the right, broken down to world regions. One can clearly see that Rotterdam handles mainly imports, with more than 281 million tons of cargo being unloaded, while only 88,2 million tons of cargo are being loaded onto ships.

Next I flipped inbound and outbound flows to the same side. However, I think that by this the diagram loses somehow, also because some purple flows (outbound to Africa and Oceania) are too thin.

In the third version, I added a shape for the balance difference between inbound and outgoing goods.

Tell me what you think about theses Sankey diagrams. It would be interesting to compare Rotterdam to other ports. Shanghai, for example, might have the opposite picture with much more exports, but I haven’t found any data yet to show this. And, if we are talking cargo traffic: how about doing a passenger Sankey diagram for one of the international airports in the U.S. (by origin/destination continent?, by airline?)

The first Sankey diagram

A scan of one of the first – if not THE first ever – published Sankey diagrams has now been added to the Dutch and German Wikipedia articles. Actually I had always wanted to get hold of a digital version of this this energy efficiency diagram published by Captain Henry R. Sankey in 1898 in the Minutes of Proceedings of The Institution of Civil Engineers. Vol. CXXXIV, Session 1897-98. Part IV.

First Sankey diagram published 1898 in JIE (Source: Wiki Commons)

Click here to see the image in original size.

Sankey used this novel type of diagram to represent energy flows and energy losses in a steam engine, comparing it to an ideal steam engine.

Decentralized Energy Benefits

The World Alliance for Decentralized Energy (WADE) runs a website on decentralized energy, called localpower.org. It has a strong educational element, and shows the benefits of producing energy locally, rather than in central power plants.

“Centralized power plants waste huge amounts of energy because their heat output cannot be used locally. Efficiency of the US electricity system, for example, is even lower today than in the early 20th century, and far below its potential.”

WADE - Showing the losses of centralized power plants

The Sankey diagram shown on the website (full size image) illustrates the losses of centralized power generation and is explained as follows:

The large red arrow represents energy from all fuels wasted in the form of waste heat. Capturing waste heat then clearly represents the largest source of potential for efficiency improvement. (…)
The smaller red arrows represent power consumed by the power plants themselves and the power lost during transmission and distribution respectively. The yellow arrows represent the actual useful energy derived from the original fuel inputs – about a third of the actual energy society should be aiming to use.

I won’t be going into the pros and cons of decentralized energy or centralized power, but rather highlight the good and the weak points of how Sankey diagrams are presented: This Sankey diagram doesn’t show any units, a fact that makes it susceptible to criticism. The insterstices in the green area on the left, meant to be separation lines, are somewhat strange (they make me think of an ancient Mayan comb), and do of course conflict with the idea of maintaining arrow width to scale. Lastly, the large arrow heads on the right side overdo the real width, underpinning the statement that a large portion of energy is being lost.

Cardboard and scissors to make Sankey diagrams

The website of Nottingham City Schools offers a variety of materials that can be used by teachers in their courses. One of the key areas in the science field is ‘energy’.

The site has a demonstration of how Sankey diagrams may be used to represent transfer of energy, including a PowerPoint and “stories”, for which pupils can create a Sankey diagram by using tokens cut from cardboard.

I think this is a great idea, as it supports the understanding of the energy topic with a haptic and, very importantly, a visual approach.