Flow in a Flash: The Art and Insight of Sankey Charts

Executive Summary

Sankey charts are a powerful tool in the visualization arsenal, capable of depicting the flow of energy, materials, or costs in an intuitive and visually appealing way. These charts provide a unique ability to represent process flow where the width of an arrow or line indicates the magnitude of the flow. In this article, we’ll delve into the art and science of creating Sankey charts and explore their various applications across industries.

An Overview of Sankey Charts

What is a Sankey Chart?

Invented by German mechanical engineer Maximilian von Sankey in the 19th century, Sankey diagrams, or Sankey charts, are a type of flow diagram used to display the quantities of flow, workflow, or the energy. They feature arrows pointing from an input source to several process steps and, finally, to a single output. The thickness of each arrow represents the amount of the process or flow it depicts.

Why Use a Sankey Chart?

Sankey charts are beneficial for their ability to:

• Show the efficiency of a process or energy flow at a glance.
• Highlight areas where materials, energy, or resources may be wasted.
• Provide a visual understanding of complex interactions, which is invaluable in troubleshooting and optimization.
• Enable comparisons within a system or between different systems.

Crafting the Art of Sankey Charts

Creating a Sankey Chart

To create a Sankey chart, follow these steps：

1. Define the Data Structure: Establish how data flows through your system. Identify the inputs, processes, outputs, and any intermediate steps.

2. Select the Software Tool: There are several tools available to help you build Sankey charts, such as Sankey Diagrams, Cytoscape, or Tableau Public. Choose a tool that fits your data structure and personal preference.

3. Design the Diagram Layout: Decide on the visual representation of your system (e.g., horizontal or vertical).

4. Assign Flow Quantities: Assign measurements to each flow. Ensure the data is accurate to depict the real-world system accurately.

5. Visualize the Data: Using the tool, map your data points and make the diagram. Be sure to maintain the width of the flow arrows proportional to the amount of flow they represent.

6. Annotate and Refine: Add labels and a legend to your diagram. Adjust colors, font, and other visual elements to enhance clarity and readability.

The ScienceBehind Sankey Diagrams

The science lies in accurately representing the flow. When creating a Sankey chart, remember that the key feature is the size of the arrows. The following rules can help you craft an accurate Sankey chart:

• Do not divide the flows. Each flow is a single process or system.
• Use consistent units of measurement.
• Represent parallel flows with parallel arrows when accurate comparison is needed.
• Use different arrows to represent different types of flows, such as energy, materials, and finance, if applicable.

The Insight in Action: Applications of Sankey Charts

Industrial Processes and Energy Flow

In manufacturing and energy production, Sankey charts allow engineers to identify inefficiencies and areas of potential improvement. For example, in a steel mill, a Sankey chart can illustrate how energy is converted and lost at various stages of production.

Environmental Studies

Sankey charts are a great tool for sustainability and environmental scientists. They can show the flow of water, air, or waste and how different processes and human activities affect these natural systems.

Finance and Ecosystem Services

In the financial sector, Sankey charts can illustrate how funds are allocated across a company or a portfolio. Similarly, in ecosystem studies, they can represent the exchange of ecosystem services such as carbon sequestration or biodiversity loss.

Supply Chain Optimization

For managing supply chains, Sankey charts can help visualize complex logistics and track materials or products as they flow through various steps in the supply chain. This allows for better production planning and reduction in transportation times and costs.

Traffic Analysis

Transportation planners use Sankey charts to analyze traffic flow, such as car movements on highways or public transport routes. It helps to identify bottleneck regions where traffic congestion is highest.

Conclusion

The art and science of creating Sankey charts are invaluable for managing data flow, optimizing processes, and identifying inefficiencies. By leveraging the power of these powerful visual tools, businesses and scientists can better understand complex systems and take actionable insights from their data. While creating Sankey charts may require careful planning and precision, the insights gained are often priceless, propelling progress and efficiency in a wide range of industries.

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