In 1898 the Irish engineer and captain H. Riall Sankey constructed a diagram that described the energy efficiency of a steam engine.1 Sankey diagrams became a widely used visual tool to characterize energy flows in any energy system, among many other applications.
Here are some tips to understand the application of Sankey diagrams to national energy systems:
1. Moving from left to right, the diagram represents the extraction, transformation, and consumption of energy. The width of an arrow (or flow) represents the quantity of energy.
2. Nodes (the rectangles) represent sources (biofuels, nuclear), transformation processes (power plant, oil refinery), and end use sectors (transportation, industry, residential, and commercial).
3. Distinguish between (a) primary “raw” energy which is energy in natural form before any transformation (crude oil, coal, natural gas, solar radiation, wind, uranium), and (b) secondary energy that has been transformed from primary sources (electricity, refined petroleum products like diesel, gasoline and jet fuel).
4. Energy “enters” in two ways: the extraction of domestic sources and via the import of primary energy (crude oil) or secondary energy products (gasoline).
5. Identify energy losses such as waste heat or electric transmission losses. These losses are typically represented with arrows leading to “waste” or “losses”nodes or dissipating away.
6. How reliant is a country on energy imports to meet supply needs, and on energy exports that generate revenue?
7. Examine the relative shares of each type of energy in the overall supply, and the relative shares of each category of energy end use.
8. Roll your cursor over a flow or node to see the associated quantity of energy. Units are terajoules. Data are for 2022.2
1 Kennedy, A. B. W., and H. R. Sankey. “The Thermal Efficiency of Steam Engines. Report of the Committee Appointed to the Council Upon the Subject of the Definition of a Standard or Standards of Thermal Efficiency for Steam Engines: With an Introductory Note. (including Appendixes and Plate at Back of Volume).”, January 1, 1898. https://doi.org/10.1680/imotp.1898.19100. https://www.energyinst.org/statistical-review
2 United Nations, Department of Economic and Social Affairs, Statistics Division,”Energy Balance Visualization,” accessed December 30, 2024, https://unstats.un.org/unsd/energystats/dataPortal/
