Sankey diagrams are powerful tools for visualizing the flow of materials through complex systems. By depicting processes with flow lines showing how much of the material is moved from one process to another, they offer a clear, intuitive understanding of complex systems or processes. This comprehensive guide aims to help you understand material flows and how to interpret Sankey diagrams effectively in your analysis.
**What is a Sankey Diagram?**
Sankey diagrams are stream graphs that display the magnitude of flow from one energy or material to another. They were designed by the German mechanic and engineer, Albert Sankey, in the late 19th century and have since become widely used in various fields, from engineering to economics to ecology.
The diagram consists of horizontal and vertical arrows, which represent the flow of materials, energy, or information. The width of the arrows represents the magnitude of the flow, with wider arrows indicating a greater flow capacity. Sankey diagrams are also often characterized by their directionality, where the flow of materials is represented from a source to a sink or from inputs to outputs.
**Interpreting Sankey Diagrams**
Understanding and interpreting Sankey diagrams involves breaking down the diagram into its primary components and considering several key aspects:
1. **Flow Lines**: The main part of the diagram is made up of the flow lines themselves. These are arrows that begin at a source and end at a sink, with the width of each arrow indicating the quantity of material being moved. Larger arrows represent higher flows, and smaller ones represent lower flows.
2. **Processes**: The flow lines are divided into processes, which are the components that the material passes through. Each process can be a physical change, a transformation, or a human-made or natural step in a process.
3. **Energy and Material Balance**: Sankey diagrams demonstrate the efficiency of a process by indicating the amount of material or energy lost at each step. For instance, an arrow that terminates before reaching the final process might represent an unused energy source or recovered waste product.
4. **Directionality and Flow Order**: The directionality of the flow lines helps to visualize the sequence of steps within a process. It’s important to pay attention to the direction in which the materials are moving to ensure proper interpretation of the process flow.
5. **Sources and Sinks**: The source is where the flows began, and the sinks are where they ending. These might be the beginning and end points of a manufacturing process, or they might represent a point where energy or material is emitted into the environment.
6. **Legend and Units**: Ensure that you understand the legend and units of the Sankey diagram. This includes the values represented by arrow widths, as well as any labels or additional information that can help contextualize the flows.
**Best Practices forAnalysts**
1. **Start with the Objective**: Before interpreting material flows, clarify what you want to understand—efficiency, energy consumption, waste, or material balance. This will shape your approach to analyzing the diagram.
2. **Analyze Process Efficiency**: Calculate the efficiency of the processes by comparing the total input to the output. Look for bottlenecks or inefficiencies where the material or energy flow is significantly lower than it could be.
3. **Identify Hotspots and Deadends**: Hotspots are areas where a lot of material is moving through quickly, while deadends are spots where there is little to no flow. Both can offer insights into areas of concern or potential improvements.
4. **Compare Sankey Diagrams Over Time**: If you are analyzing processes that evolve over time, compare different Sankey diagrams to track changes in material flows, efficiencies, and other factors.
5. **Validate Your Findings**: Make sure to cross-reference your analysis with other data or reports to ensure the accuracy of your insights.
By combining this comprehensive understanding of material flows with the ability to interpret Sankey diagrams, you can reveal valuable information about the processes and systems under study. Whether in industrial analysis, economic modeling, or environmental studies, Sankey diagrams are versatile tools that can clarify complex relationships and lead to meaningful data-driven decisions.
