Picturing Energy Flows: A Creative Guide to Crafting Sankey Charts

Sankey diagrams, named after Irish astrophysicist Sankey and popularized by British engineer John Herschel in his 1877 book “Stream Flow,” are powerful visualization tools that depict the flow and distribution of energy, material, or information within a system. These diagrams effectively illustrate how inputs are transformed through multiple steps into the final outputs, highlighting efficiencies and losses along the way. In today’s world, where energy efficiency and sustainability are paramount concerns, Sankey charts have become indispensable for evaluating the energy flows within a system, be it a household, a city, or an entire country. This guide provides a comprehensive look into the creative process of crafting effective Sankey charts, making them a valuable tool for understanding complex energy systems.

Understanding Sankey Charts

A Sankey diagram consists of several components:

1. Source: The initial input or source of energy or materials.
2. Input pipes (or arrows): These represent different types of inputs as they enter the system.
3. Output pipes (or arrows): These represent the outputs, either as final products, waste, or by-products.
4. Step pipes (or arrows): These depict energy transformation or material conversion within the system.
5. Flow magnitude indicators: This includes the width of the pipes, which represents the magnitude of flow.
6. Flow direction indicators: These might be implied or explicitly shown with arrows, often unnecessary due to the universal convention of information or energy flowing from left to right in Western cultures.

Sankey diagrams are most useful when there are multiple inputs, a series of conversion steps, and multiple outputs. They are widely used in various fields, including energy analysis (oil, water, electricity), waste management, and supply chain analysis, among others.

Crafting Effective Sankey Charts

1. Choose the Right Sankey Chart Software

Selecting the right software is crucial for the creation of Sankey diagrams. Tools like Tableau, Microsoft Excel, and SankeyMATIC can help you visualize the energy flows between sources and sinks. Each software has its strengths and limitations, so it’s essential to choose one that suits your data and design needs.

2. Define Your Data and Objectives

Before diving into the design, define the system you want to represent and the objectives behind your Sankey chart. This clarity will guide the data collection and ensure that your chart addresses your objectives effectively. Data should include source, transformation steps, and sinks, along with the magnitude of flow for each segment.

3. Collect the Right Data

Accurate data collection is the backbone of an effective Sankey chart. Collect data accurately for each input, transformation step, and output. This information should be quantified and verified for correctness.

4. Use Width to Represent Amount

The width of the arrows in a Sankey diagram is proportional to the amount of energy or material being transferred. This scale helps in quick interpretation of the data. Ensure your data is accurately represented through the width of the arrows.

5. Label Your Diagram

Clear, concise labeling makes your Sankey chart more understandable. Label your sources, inputs, transformations, and outputs. Additionally, include a legend or explanation of the data scale for better interpretability.

6. Consider Color

While color isn’t necessary, it can enhance the visual impact of your Sankey diagram. Use colors to help users distinguish different types of energy, materials, or classes. However, be cautious with colorblind users and ensure your color scheme doesn’t hinder comprehension.

7. Review and Revise

Your Sankey chart should clearly communicate your data’s essence. Review your chart for readability and accuracy. Ask for feedback from others to identify any misunderstandings or areas for improvement.

8. Stay Current

As the system you’re analyzing evolves, so too must your Sankey diagram. Regularly update your chart to keep it accurate and relevant.

Applications of Sankey Charts

Sankey diagrams can be applied in various contexts to illustrate the flow of resources, energy, and information. In the context of energy flows, these diagrams help in evaluating the efficiency and sustainability of a system. They can also be used to plan the energy transition towards renewable energy sources by visualizing the potential savings and losses.

Conclusion

Sankey diagrams are a powerful tool for visualizing and understanding complex energy flows. By following this guide, you can craft effective Sankey charts that communicate your data clearly and are useful for decision-making and public understanding. Remember, the key to an effective Sankey diagram is the clarity and accuracy with which you represent your data. Whether used for research, teaching, or public engagement, Sankey diagrams are a valuable asset in understanding our energy world.

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