Sankey charts, a specialized type of flow diagram, have historically been a tool of choice for depicting material and energy flows in processes and systems. They visually represent the quantities of materials, energy, or cost that move through a system by showing a series of parallel, horizontal lines (or streams) that widen and narrow to indicate the magnitude of the quantities moving along each path. In this article, we delve into the science and art of mastering Sankey charts to optimize resource flow, exploring their construction, interpretation, and application in a variety of contexts.
**The Science: The Underlying Principles**
The science behind Sankey charts is rooted in flow analysis. Flow analysis is an interdisciplinary field drawing from various subjects including industrial engineering, environmental science, and thermodynamics. It provides a systematic approach to understanding how resources flow through a complex system and how to identify inefficiencies or areas for improvement.
The core of the Sankey chart methodology is based on the following principles:
1. **Conservation of Mass and Energy**: A Sankey chart begins with assuming that the total flow into the system is equal to the total outflow, ensuring the conservation of materials or energy.
2. **Flow Magnitude**: The width of each stream in a Sankey chart represents the magnitude of flow of a particular type. The wider the stream, the greater the flow.
3. **Efficiency Representation**: Sankey charts are designed to visually display the efficiency of a process or system. Inefficiencies (often represented as “lost” or “rejected mass” or “waste”) are depicted as smaller branches that leave the main stream.
4. **Stream Connection**: Each flow stream is connected to other streams. These connections indicate a transformation or transfer of resources between different parts of the system.
**The Art: Designing an Effective Sankey Chart**
Creating an effective Sankey chart is neither purely a scientific nor a mathematical endeavor; it also requires a degree of artistry:
– **Stream Organization**: Carefully arrange the streams to reflect the dynamics of the system and provide clarity. Group related streams together and use logical flow directions.
– **Symmetry and Consistency**: Sankey charts benefit from a sense of symmetry and consistent line width scaling to make comparisons easier.
– **Stream Width**: Consistent width scaling makes it easier to compare the quantities between different streams. It is important not to overcrowd the chart with too many very thin streams; otherwise, the message can become lost.
– **Color Coding**: Use color coding to distinguish different types of flows. Ensure that the same colors are used consistently throughout the chart.
– **Labeling**: Clear and concise labeling is crucial. Properly locating and sizing all numerical and text labels is part of the visual storytelling that can help the viewer quickly digest the information.
**Applications of Sankey Charts**
Sankey charts have a wide array of applications, some of which include:
– **Energy Flow Diagrams**: Illustrating energy efficiency in power plants or building systems.
– **Material Flow Analysis**: Showing the flow of materials or waste products in manufacturing processes and in society at large.
– **Financial Flow Analysis**: Representing the allocation of financial resources across different departments or projects within a company.
– **Environmental Analysis**: Demonstrating the lifecycle of products, the movement of pollutants, or the potential for resource conservation.
– **Network Analysis**: Modeling the flow of information or communication within a network.
Mastering the art and science of Sankey charts enables stakeholders to understand system-level resource flow dynamics more quickly and more effectively. Whether it’s a design engineer seeking to reduce losses in a manufacturing process or a sustainability professional tracking the lifecycle of goods, Sankey charts offer an invaluable visual tool for optimizing resource flow in a variety of industries and systems. By incorporating creative and strategic decision-making into the creation of these charts, practitioners can harness the power of this art and science to improve efficiency and inform effective strategies.
