Sankey diagrams, originally introduced by Captain Sankey in the 19th century to study the efficiency of heat engines, have evolved to become sophisticated tools for visualizing complex flow and network relationships. Often referred to as “flow diagrams,” these specialized charts are capable of succinctly depicting the flow of material, energy, or information through a system. Their distinct, streamlined design, with arrows that follow the paths of the flow, is a powerful way to understand the dynamics at work within a network. Let’s dive into the intricacies of Sankey charts and learn how to decipher these visual masterpieces.
**What Are Sankey Charts?**
At their core, Sankey charts display directional flows between processes or entities in a network. The flow is typically represented by a thin arrow which contracts and expands based on the quantity of flow. Unlike typical flowcharts, which focus on individual processes within a system, Sankey charts excel at illustrating the overall distribution and transformation of flow. By highlighting where energy or material is captured or lost, Sankey diagrams provide a birds-eye view of efficiency and bottlenecks in complex systems.
**How Do Sankey Charts Work?**
There are a few essential components to understand when working with Sankey charts:
1. **Flow Lines**: These are the main feature of a Sankey diagram, with width proportional to the amount of flow. Thinner lines represent low flow, and wider lines indicate high flow.
2. **Nodes**: Nodes are the starting or ending points where flow enters or exits a process or a connection between two processes.
3. **Processes**: Processes are the steps or actions through which flow is transformed in the network. Sankey diagrams can depict a process as anything between a few and many steps, each represented by a node with incoming and outgoing flow.
4. **Inputs and Outputs**: These are the resources, energy, or materials that are entering and leaving the system.
**Interpreting the Diagrams**
Here’s how to make the most of your Sankey chart:
1. **Scale**: It is important that Sankey chart flows are dimensionless to avoid misrepresenting quantities. Focus on the relative flow rather than absolute values.
2. **Look for Trends**: By observing the thickness of flow lines and how they change direction, you can identify where resources are consumed, wasted, or conserved.
3. **Identify Bottlenecks**: Notice if there are any particularly wide nodes where a large amount of resources enter or exit. These indicate high congestion points that might be improved upon for greater efficiency.
4. **Comparisons**: It’s helpful to compare several Sankey diagrams to see how flows change over time or between different situations.
**Common Applications**
Sankey charts are used across a variety of industries and fields, including:
– **Energy Flow**: Visualize where and how energy is being produced, consumed, or wasted.
– **Financial Flow**: Represent cash flow through an organization, project, or business relationship.
– **Material Flow**: Track the flow of materials within manufacturing processes and supply chains.
– **Environmental Analysis**: Assess carbon flows or ecosystem services in ecosystems or communities.
**Closing Thoughts**
Sankey charts are a nuanced method for visual analysis, but once you understand the principles, they offer an intuitive grasp of the systems you’re studying. The diagrams’ ability to capture flow at-a-glance makes them invaluable in identifying areas for potential optimization, whether in an industrial setting or within human societal structures. With their unique approach to visual storytelling, Sankey charts are a potent tool in the modern data visualization arsenal.
