Sankey diagrams are an elegant and powerful tool for visualizing complex material flows. Their unique design effectively communicates the magnitude and direction of flow from the source to destination, making them an indispensable aid in a variety of industries, from energy and manufacturing to environmental research. However, while the visual representation is clear, the underlying data and interpretation can be complex. This article aims to demystify the art of interpreting Sankey diagrams, helping professionals master this valuable skill.
The Art of Diagram Design
Sankey diagrams represent flows as arrowed lines that are wide or narrow, depending on the amount of flow. The width of these lines is the key to understanding the Sankey diagram. A wide line, often referred to as a ‘main vector,’ indicates a flow of greater magnitude, while a narrower one signifies a lesser flow. This visual representation allows us to quickly identify where the primary flows occur and potential bottlenecks in the system.
It’s important to note that the area enclosed by a flow vector is not used for conveying information. The significance is in the width and direction of the flow; the actual area does not affect the diagram’s meaning.
Laying the Foundation: Understanding the Components
To interpret a Sankey diagram, it is essential to understand its fundamental components:
1. Streams: These are the flow paths, represented by the arrows. They can be for materials, energy, or any other measurable quantity you’re analyzing.
2. Nodes: These are the points where streams terminate, indicating a change in the status of a material. They can be production points, transformation points, or even sources and sinks, which are the entry and exit points of a system.
3. Vectors: The width of vectors signifies the magnitude of flow. The thicker the vector, the greater the flow.
4. Labels: Ensure that the Sankey diagram includes clear labels for streams, which should state the amount of flow in a unit that is clearly identifiable and of the same scale across all vectors. Directional labels can be helpful for context as well.
Navigating the Complexity
Interpreting Sankey diagrams successfully involves several careful considerations:
**Flow Magnitudes & Relationships**
Begin by comparing the widths of the main vectors—this will give you a sense of the relative flow magnitudes. For a more detailed analysis, you may need to look beyond the primary vectors to understand the smaller ones. These can provide insights into inefficiencies, waste, or less significant flows.
**Bottlenecks & Inefficiencies**
In a Sankey diagram, bottlenecks are typically visible as narrow pathways that connect two large vectors, indicating a significant obstruction in the flow. These bottlenecks can represent areas of high resource use or inefficiency and are crucial to address for improvement.
**Energy Flows**
In energy analysis, Sankey diagrams are particularly useful. The diagrams can help identify the most energy-efficient processes and highlight areas where energy is lost as waste heat, serving as a guide for optimization.
**Environmental Impact**
Greenhouse gasses, pollutants, and waste are crucial information for environmental assessments. By analyzing the streams of these substances in a Sankey diagram, one can observe their life cycle and overall environmental impact.
**System Boundaries**
The system boundaries of a Sankey diagram are important as they can affect the interpretation. When interpreting a Sankey diagram, it is essential to understand what the boundaries are; otherwise, it may lead to incorrect conclusions.
Mastering the Art
To truly master the art of interpreting Sankey diagrams, it is best to:
1. Gain a strong foundation in their design and how they work.
2. Understand the underlying data and ensure it is complete and accurately reflects the system being analyzed.
3. Become adept at recognizing and labeling flows in a way that is meaningful and intuitive.
4. Apply them in various contexts to understand how they adapt to different datasets and systems.
Conclusion
Interpreting Sankey diagrams is a skill worth mastering, as they are powerful tools for visualizing the flow of material, energy, and data. By understanding the diagram layout, components, and underlying data, professionals can navigate their complexity to improve efficiency, reduce waste, and make better-informed decisions within their respective domains. Whether you’re an engineer, environmental scientist, or an operations manager, harnessing the wisdom of Sankey diagrams can set you on the path to mastering the art of interpreting complexity.
