Sankey diagrams have been a part of the data visualization toolkit since the early 20th century, originally created by English engineer William Playfair in 1858. Despite their age, these iconic charts persist as a powerful tool for understanding and analyzing processes with multiple interconnected components. Though they may appear complex at first glance, understanding the principles behind SANKEY diagrams is critical for those working in fields where material flow, energy usage, or other complex systems must be analyzed to enhance insights and efficiency. This article seeks to demystify Sankey diagrams, equipping readers with the knowledge to not only interpret but design them effectively.
### A Brief Overview of Sankey Diagrams
At their core, Sankey diagrams are a variant of flow diagrams that illustrate the quantity of material, energy, or cost moving through a process. They do this by displaying the flow as a series of parallel arrows, with the width of each arrow indicating the volume or intensity of flow. Each arrow typically starts from a source (inlet) and ends at a destination (outlet).
### Key Features of Sankey Diagrams
While the concept is straightforward, constructing an effective Sankey diagram involves understanding several key components:
1. **Flow Representation**: While arrows are used to depict the flow, the width of each corresponds to the amount of material, energy, or cost in the flow path. The wider the arrow, the higher the quantity moving through it.
2. **Thermal/Pressure Gradient**: The width of the arrows often reflects the pressure and thermal gradient of the flow. This is done by placing the narrow end at a high-pressure/temperature region and the wider end at a lower-pressure/temperature region.
3. **Heat Flow**: In the realm of energy systems, Sankey diagrams can represent the distribution, transformation, and loss of heat within a system, visually emphasizing inefficiencies.
4. **Loss and Waste**: Sankey diagrams can also highlight areas of loss or waste, such as unused materials, inefficiencies in energy conversion, or other areas where resources are not utilized optimally.
### Why Sankey Diagrams Are Useful
The utility of Sankey diagrams emerges from their ability to convey three major advantages:
1. **Quantitative Visualization**: With Sankey diagrams, it is often possible to make precise and accurate measurements of the quantities involved in the processes being analyzed.
2. **Efficiency and Inefficiency Analysis**: By observing the width of the arrows, one can quickly identify where the majority of resources are consumed and where inefficiencies or waste might occur.
3. **Comparative Analysis**: Sankeys are invaluable for comparing different processes, systems, or scenarios side-by-side, allowing for a more nuanced and direct comparison.
### How to Design a Sankey Diagram
Creating a well-designed Sankey diagram requires careful planning and systematic organization. Here are some actionable steps:
1. **Define the System**: Clearly outline the processes and the system under study, including its inputs and outputs.
2. **Break Down the Processes**: Identify the stages of the process and the pathways through which materials or energy flow.
3. **Estimate the Quantities**: Gather data on the amount of each component being flows through your system. This can involve statistical calculations, direct measurements, or simulation.
4. **Select Appropriate Nodes**: The nodes are the points at which the flow connects to the system. Choose these carefully to represent the processes accurately.
5. **Layout the Arrows**: Use a tool likeSankey Maker or draw by hand, starting from the sources and culminating at the sinks, ensuring flows do not intersect.
6. **AdjustArrow Sizes**: Reflect the actual quantities with the width of the arrows. Ensure that they add up to 100% to make the Sankey a circle of flow.
### Conclusion
Sankey diagrams may initially seem perplexing, but understanding their principles and applications can unlock valuable insights into a range of different systems and processes. Their unique visual format highlights the flows and helps to identify inefficiencies and opportunities for optimization. By familiarizing yourself with Sankey diagrams, you can contribute to the improvement of system analyses across a multitude of disciplines, fostering a more efficient use of resources and helping organizations make informed, sustainable choices.
