Flow Visualized: The Zen of Sankey Art
Introduction
Flow visualizations have been a cornerstone in understanding and analyzing process systems for over a century. Sankey diagrams, also known as Sankey plots, are a special kind of flow visualization that has gained popularity due to their ability to elegantly depict energy transfer and materials flow in systems. In this article, we will delve into the art and science of Sankey chart creation and explore their diverse applications across industries.
What is a Sankey Diagram?
A Sankey diagram is a type of chart that provides a visual representation of the energy or material flow within a system. Developed by Max Schulze in the mid-19th century, these diagrams are named after Dr.sankey, an English engineer who utilized this method to analyze steam engines.
Key Characteristics:
- Directional Arrows: The main feature of a Sankey is the flow of materials or energy in one direction along an arrow, which typically runs from a “source” (like an intake) to a “sink” (like an exit).
- Width Scales: The width of each flow arrow scales with the quantity of material or energy it represents. This makes it easy to compare the magnitude of flows across different parts of the system.
- Efficiency: Sankey diagrams visually express the efficiency of a process by showing the amount of energy or materials lost in the form of side streams and losses.
- Consistency: The flow lines never cross each other, and all lines start and end at the same scale, which provides a clear comparison and helps maintain the overall balance.
Creating Sankey Charts
Creating a Sankey diagram involves several steps that emphasize the intersection of data representation and visual aesthetics:
Data Collection and Organization:
Begin by collecting all relevant data about the process under examination. Organize this data in a logical, hierarchical structure, categorizing different inputs, outputs, and the processes they undergo.
Setting Up the Blueprint:
Decide the scale of your Sankey diagram. Determine the starting and ending points of your flow, and plot them accordingly. Choose an appropriate arrangement for the process steps and nodes.
Drawing the Edges and Flows:
With the structure in place, draw the flow lines, ensuring they don’t cross each other and are proportional to the amount being transferred. Represent the process steps or energy conversions using nodes that the lines connect.
Visual Tweak:
Experiment with line width, color schemes, and patterns to enhance readability and convey information effectively. Use these visual elements to emphasize efficiency, potential savings, or areas for improvement.
Validation:
Finally, review your Sankey diagram for accuracy and consistency. Validate the widths of the arrows and check that each process and transfer is correctly represented in the diagram.
Applications of Sankey Diagrams
The versatility of Sankey diagrams means they find applications across various sectors:
Engineering and Design:
Sankeys are used in engineering to analyze energy efficiency, such as in power plants, vehicles, and buildings. Designers use them to optimize product designs by visualizing material and energy flows.
Sustainability Analysis:
Sustainability professionals use Sankey diagrams to map the environmental impact of products, processes, or systems over their entire lifecycle.
Business and Financial Analysis:
In business, Sankeys can help track money flows, such as in supply chains, investment portfolios, or cost analyses.
Urban Planning:
Sankey diagrams can be applied to study the flow of individuals, goods, or services within cities, aiding in urban planning and infrastructure development.
Education and Communication:
Sankeys provide an engaging way to convey complex concepts during presentations. They can also be educational tools, helping students understand intricate dynamics and relationships between flows.
Conclusion
Sankey diagrams are more than just a method of visualizing data; they are a gateway to understanding and interpreting the relationships between flows and transformations in a process. With the right approach to chart creation, Sankey diagrams can offer deep insights, streamline decision-making, and foster a better understanding of complex systems in a variety of fields. Like a piece of art, the essence of Sankey diagrams lies in the balance and harmony between data and form.
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