Interesting blog post by Steve Wexler of Data Revelations. Long article, long title: “Circles, Labels, Colors, Legends, and Sankey Diagrams – Ask These Three Questions”.
The really interesting part for the Sankey diagram aficionados is Steve’s advice on when to use Sankey diagrams, and when you should avoid using them.
Steve illustrates his point with the below example by ‘Music Major – Data Miner’ Jeffrey A. Shaffer (original post is here)
A combination of a stacked bar chart with a distribution diagram, nicely decorated with a trumpet … “Within this context, this very creative chart works”, Steve writes.
He then goes on and shows another one by Shaffer, also a distribution diagram: the original pie chart data from an energy bill has been redesigned and was presented as a distribution diagram (two stacked bars with bands to link them)
In this case, Steve concludes, the choice of a Sankey diagram is maybe not that wise, since the actual important information (44% of energy cost is for heating) doesn’t really come across quickly and clearly. A bar chart might work better here. Sankey diagrams can create a “cool!” or a “crap!” response, depending on the context. See the original Shaffer post here.
Adding my 2c from a technical perspective I would say that both diagrams have a shortcoming: The bands don’t maintain their width as they cross over the others diagonally. Somewhat acceptable in the trumpet diagram as the right bar on the right side listing the music composers is higher than the one at trumpet bell (sound spreading out). Not acceptable in the second diagram where the two stacked bars have the same height. This is obviously an error in the curve radius calculation (read ‘The Math Behind those Curves’)
Another Sankey diagram of Canada’s energy flows is featured in a blog post titled ‘Dividing the Big Picture: Visualizing Provincial Diversity’. The post appeared May 5, 2014 on the Canadian Energy Systems Analysis Research (CESAR) blog by David B. Layzell, Professor at the University of Calgary. It is a follow up to a previous CESAR blog post that showed “the big picture” for Canada (featured in a recent post here on the blog).
“The Sankey diagram below shows only the domestic portion of Canada’s energy systems. (…) It also shows how much of that demand is met by oil/petroleum (red), natural gas (blue), electricity (yellow), biomass-derived products (green) or other energy resources.”
Flows are in GJ per capita. This relative unit is different to the other national energy flow diagrams I have presented here on the blog. But it is interesting for differentiating energy consumption in the different provinces.
The article explains:
“There are significant inter-provincial differences associated with each end-use category. For example, British Columbia (BC) residents had the lowest residential energy use in the nation, at 63% of the per capita energy use in Alberta (52 GJ/capita), the national leader in this category. The balmy BC climate compared to what Albertans face each winter accounts for most of this difference. However, our model also draws on government data showing that many BC buildings tend to be better insulated than those from much colder Alberta.”
Check out all Sankey diagrams tagged ‘Canada’ here.
Featured on the Canadian Energy Systems Analysis Research (CESAR) blog is the below Sankey diagram on Canada’s Energy Flows in 2010. The article reports about a new model called ‘CanESS’ (Canadian Energy Systems Simulator) developed by Technologies Inc. and the University of Calgary.
Pulling together data from different sources the tool can visualize energy flows as Sankey diagrams.
The big picture of Canadian energy in 2010 is as follows:
“Canadian primary energy production in 2010 was nearly 25,600 PJ, and after including 3,700 PJ of imports, total primary energy availability was 29,500 PJ. As the Sankey diagram shows, 58% was exported, with the remaining 42% or 12,500 PJ being used domestically, 910 PJ for non-energy applications and 11,652 PJ for the provision of energy end use services to Canadians.”
There is an interactive version that allows you to choose the year (1978-2010), to break down the data onto each Canadian province, or change the unit. Try it out!
An energy flow chart for energy use in the residential building sector is shown on the Autodesk Sustainability Workshop page ‘Measuring Building Energy Use’. There is also a similar Sankey diagram for energy sources consumption in the commercial building sector.
Both are taken from a Pacific Northwest National Laboratory (PNNL) report from 2006 prepared for Department of Energy (DOE) titled ‘Energy End-Use Flow Maps for the Buildings Sector by D.B. Belzer (PNNL-16263).
Residential building sector energy flow chart:
Commercial building sector energy flow chart:
Both Sankey diagrams are built up the same way. The top part of each diagram shows electricity generation, the bottom part the energy flows for heating. Significant conversion and transmission losses can be identified by the arrow branching out at the top. Flows from the left represent the energy sources: coal (brown), natural gas (blue), biomass/solar (green). To the right the flows are broken down to the individual consumption, such as heating, cooling, lighting, other electric appliances, etc.
All units are in quadrillion BTUs for the U.S in 2004.
Dutch tech consulting firm ‘Water and Energy Solutions’ looks at optimization opportunities and cost saving potential in industrial production sites.
Their services offer is advertised with this sample Sankey diagram.
Their approach called “Flux Technology” is a methodology that “first considers a production site at the largest possible scope, focusing primarily on intersecting process and utility streams. At different scope levels we analyze site, plant(s), unit operations, equipment and general operations both qualitatively as well as quantitatively.”
From the Swiss Energy Statistics for 2005 published by BFS comes the following Sankey diagram.
Flows are in GWh. The large pale streams on the left are imports and exports. The vertical bands are domestic energy production (different types of electricity generation) at the top. A breakdown of the consuming sectors is shown in the lower part.
Will try to dig out a more recent energy balance for Switzerland to compare.
One image in particular caught my attention. This is described as “Energy Display System” created by CSIS in the 70s
(via Energy Education References Wiki)
You all know those national energy flow Sankey diagrams I show here regularly? Now imagine the same type of image as a series consecutive frames for several years. This would produce a kind of animated gif or movie showing changes over time.
The above must be an early 3D version of this. The diagrams are mounted on what seems to be acrylic glass…