Sankey diagrams, named after Edward Ford Sankey, a British engineer who first used them in the late 19th century to visualize steam flows used in ship engines and factories, have evolved significantly since their inception. What began as a tool for understanding the energy balance in steam systems has expanded to become one of the most versatile and visually compelling tools for visualizing flows of energy, resources, materials, and data in a wide range of industries and fields. Whether they are used to analyze the carbon footprint of a construction project, the data transfer rates within a complex IT infrastructure, or the financial flows in a portfolio, Sankey diagrams bridge the gap between the abstract and the tangible, making complex data sets understandable and engaging.

The Basics of Sankey Diagrams

At their core, Sankey diagrams are flow diagrams that show data conversion steps. Unlike traditional charts that simply plot data as points or lines, Sankey diagrams visualize data as the width of lines. The area of these lines corresponds to the magnitude of the quantity they represent; in other words, the wider the line, the greater the flow. This makes Sankey diagrams particularly effective for analyzing and communicating flows, whether they are the energy transfers in a solar panel system, the financial contributions to an organization, or the data flows within a network.

Creating a Sankey Chart

Creating a Sankey diagram involves several steps, starting with data preparation. The data typically consists of a series of inputs and outputs from a process, with each step having a corresponding flow amount. In Excel, for example, this might involve setting up columns for the source (input), destination (output), and quantity of the flow. The quantity is crucial for determining the width of each link in the diagram, which should represent the size of the energy, data, or resource flow accurately.

Once the data is organized, the next step is to use a tool or software to visualize the data as a Sankey diagram. Many visual toolkits and programming libraries support Sankey diagram creation, including Python’s Plotly, D3.js, and Tableau. These platforms offer various options for customization, from selecting different styles and themes to adjusting the node positions and link colors, making each Sankey diagram unique and tailored to its specific purpose.

Applications and Advantages of Sankey Diagrams

Sankey diagrams have myriad applications across various sectors, including energy analysis, environmental science, financial analysis, supply chain management, and data visualization. For example:

• Energy Analysis: Utilities and renewable energy companies use Sankey diagrams to efficiently map the conversion and losses of energy from generation to consumption and distribution, helping in optimizing the energy flow and reducing waste.

• Data Science: Analyzing the flow of data across systems, including data streams, databases, and platforms, is critical in big data analysis and cloud computing. Sankey diagrams help in understanding the data journey, identifying bottlenecks, and improving infrastructure efficiency.

• Manufacturing and Supply Chain: By visualizing the flow of materials, resources, and products, Sankey diagrams facilitate supply chain optimization, waste reduction, and sustainability assessments in manufacturing processes.

• Information Flow: Governments, IT companies, and other organizations use Sankey diagrams to understand the flow and interconnectivity of information across systems, databases, and networks, enhancing cybersecurity and data management strategies.

The advantages of Sankey diagrams are numerous. They are highly intuitive and accessible, making complex data sets understandable with just a glance. They also allow for easy identification of bottlenecks, inefficiencies, and paths for improvement, offering a holistic view of the system’s flow. Moreover, because they are a type of flow diagram, they can be an excellent tool for training and communication, helping both beginners and experts alike to grasp complex processes.

Conclusion

Sankey diagrams have revolutionized the way we visualize and understand complex flows. By transforming abstract data into a visually intuitive format, they not only make data analysis more accessible but also provide insights that were previously hidden. Whether for energy efficiency, data management, or financial analysis, Sankey diagrams are a powerful tool in the visualization toolkit, helping professionals and non-specialists alike to see the flow of information and resources in compelling and useful ways.

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