SANKEY

by Nicole Cardillo

A Sankey is described as a flow diagram that visualizes a medium such as energy, money, or data and how it moves between different stages. This type of visualization is important because it aids in helping people understand the behavior of data in a system. This includes the increasing and decreasing of a data series in a visualization. 

United States Energy System Sankey

The image above is a Sankey diagram displaying the United States's energy use. In my opinion I think this type of visualization is messy and difficult to understand at first glance. While we can clearly see the increasing and decreasing in the graph, as a viewer, I am unsure what each color represents without looking at the tiny text that goes along with it.

Furthermore, when I zoom into the beginning of the graph, I am unsure what each area of the visualization represents. The image below exhibits the many colors and topics that are being discussed in this Sarkey.

The red portion is labeled with the text Natural Gas Production, before it is cut off by another red bar labeled Primary Natural Gas Production. This is format is confusing to me solely because of the various words on the page that are donned upon an already confusing array of colors.

Additionally, the image below shows a portion from the very right side of the Sankey diagram. 

Each thick portion color portion branches off into these thin portions at the end of the Sankey. As someone who is unfamiliar with Sankeys, just as most people are, it is extremely difficult to understand what anything means in this graph.

Despite this, the Sankey is a great way to display an abundance of information on one scale. The blog explains, "The interactive Sankey diagram we created for ARPA-e in 2018 represents all of the energy flows in the U.S. economy, from "primary energy" sources such as coal, natural gas, oil, hydropower, solar, geothermal and nuclear power, through their transformation into intermediate sources such as gasoline, diesel and other intermediate fossil fuels, or electricity, and then their use by various sectors of the economy" (OtherLab). Popular graphs such as bar charts or line graphs may not have the ability to show all of this information, let alone display a visible trend. This would render the graph moot if it is not able to tell a story to the audience.

Nonetheless, I do not believe a Sankey visualization is a strong visualization in telling a story. It is too cluttered with colors, lines, and words, which make it extremely difficult to understand. However, the blog does provide us with insight on how to analyze the Sankey, "The diagram also represents the energy that is used in those transformations, including the energy used in generation, lost in transmission or embodied in products and materials that use energy in their production. The width of a given flow identifies the size of a given energy use and thus points the way to the most impactful interventions to reduce energy use or enable decarbonization" (OtherLab). Still, with this knowledge, I still find this Sankey difficult to understand. I would prefer to see this data presented in a line graph, where the important data is colored while the comparison data is light gray, just like the graph we saw in our first week of class.

The United States Energy Information Administration created a visualization of a bar graph from 2000–2016. This information is explicitly shown in value through each bar's height, as well as a colored legend indicating the value for each source.

In my opinion, this visualization is just as, if not more effective than the Sankey. Each category is organized along a timeline, showing us the change in values. The article explains, "Consumption of coal decreased by 9%, nearly offsetting increases in the consumption of renewables, petroleum, natural gas, and nuclear fuel" (EIA). This can clearly be seen by the vivid decrease in the brown portion of each bar over the course of time.

Conclusion

Ultimately, I do not think a Sankey is the best use of data visualization. It is too messy and difficult to comprehend. While I like how a Sankey can hold an abundance of information, sometimes less is more, especially when it comes to visualizations. Throughout this class, we have learned that it is difficult for the human brain to process images if they are too cluttered, and so I think a Sankey diagram is a prime example of a messy visualization. Therefore, I do not believe a Sankey visualization is the best way to display data.

References

“US Energy Flow Super Sankey.” Otherlab, www.otherlab.com/blog-posts/us-energy-flow-super-sankey.

Eia.gov, 2016, www.eia.gov/todayinenergy/detail.php?id=30652.

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