Home » Uncategorized » Sankey Diagrams

Sankey Diagrams

The production of energy is an incredibly complex topic. With so many factors at play (including sources, consumers, and amount used), it can be difficult to effectively visualize the data in one graphic. The National Academies of Sciences, Engineering, and Medicine maintain a collection of Sankey diagrams that attempts to depicts the energy system across the United States and more localized areas. Although not perfect, and at the cost of cohesion, they accomplish this goal.

At first glance, the diagram appears overwhelmingly convoluted. It is important to realize, however, that this particular Sankey diagram combines three into one: the first shows the distribution of energy from its sources (in color), the second shows the distribution of electricity (in gray), and the third shows what portions are considered useful versus those that go unused (in blue).

To increase intelligibility, the diagrams let the viewer make particular selections. This highlights the one part and provides numerical data, both crucial for conciseness.

In addition, the number of separate diagrams introduces the possibility for even more information to be depicted, even going beyond what the diagrams show.

Immediately, one feature proves to be advantageous: it is easy to determine what the primary sources of energy are in each area. Further, this can be important in determining how reliant particular areas are on certain sources. For instance, California relies heavily on oil (most of which is used for transportation) whereas the other region relies more on coal (most of which goes into the production of electricity). In turn, these can go on to provide insight into the context of each area; coal use is more prevalent in an area where it is mined just as oil is used more in an area that is heavily populated and on the move.

Nevertheless, these Sankey diagrams could be improved. Consider, for instance, the percent of useful energy compared to the total amount produced. Although not provided, the values can be calculated as 39.1% nationally, 27.1% across the specified region, and 40.9% in California. These are all represented by dark-blue cubes of the same side, regardless of the varying percentages. Therefore, without doing the calculations and relying on the diagrams alone, one might be led to believe the ratios are consistent across the nation, regardless of scale.

That being said, these Sankey diagrams in particular highlight the issue that more energy is wasted as opposed to put to use. While this may be concerning, it is important to mind physical limitations of energy production. The diagram points out the following:

There are many opportunities to improve our nation’s energy efficiency, but it’s impossible to avoid losing some energy as heat when converting energy from one form to another. The principles of physics place upper limits on how efficient a heat engine, power plant, or oil refinery can be.

Retrieved from : needtoknow.nas.edu.