Sankey diagrams are visualizations that can help your students learn about the flow of energy in a system. The first Sankey diagram was introduced by an Irish engineer, Captain Sankey, in an 1898 article about the energy efficiency of a steam engine. Today, Sankey diagrams are valuable tools for visualizing the flow of energy from source to services (end use). One thing that your students will notice is that in many cases, rejected energy (e.g., heat) is greater than the amount of useful energy generated!
You may already be familiar with the annual energy flow diagrams made available by Lawrence Livermore National Laboratory. The most recent flow chart is for the year 2011. A flow chart of US energy-related carbon dioxide emissions is also available (most recent is for 2010).
These flow charts can be used with students to promote active learning. The National Academy of Sciences has constructed an interactive Sankey diagram using 2009 US energy flow data titled, Our Energy System, that could be used to introduce students to this visualization tool.
Chapter 6 of the Global Systems Science online book “Energy Use” guides users through an “untangling” process where they consider the energy source with the widest path (petroleum) first to get a sense of how to interpret the flow chart. Guiding student questions are also provided. And this lesson on the energy economy, provides users with questions that can be used to dissect the US energy flow diagram from 2002, an interesting year from the author’s perspective (see References and Resources section of lesson).
International energy flow charts are also available, with the most recent set summarizing energy flow for the year 2007 for 136 countries. The link to these flow charts as well as teacher tips for utilizing these Sankey diagrams can be found by clicking here.
State-Level energy flow charts are also available, with the most recent set summarizing energy flow for the year 2008 for all 50 states. The link to these flow charts as well as teacher tips for utilizing these Sankey diagrams can be found by clicking here.