Analytical studies often benefit from the use of visual tools that succinctly communicate the intricacies of data and processes. One such tool is the Sankey diagram, which particularly excels in depicting material flows. This guide aims to demystify the use of Sankey diagrams, highlighting their construction, interpretation, and the insights they offer for a wide range of analytical studies in various disciplines.
**What is a Sankey Diagram?**
A Sankey diagram is a variant of the flow diagram, a statistical visualisation developed bysankey diagrams have proven to be invaluable in illustrating material or energetic flows within a system. A visualisation can depict complex processes such as materials entering and exiting an industrial system, energy pathways, or water usage within a city.
**Composition of a Sankey Diagram**
At its core, a Sankey diagram consists of parallel lines known as ‘流管’. Each of these lines represents a specific process or a system’s element, and the width of the line corresponds to the amount or volume of material or energy associated with the flow.
The following elements compose a typical Sankey diagram:
– **Flow Channels**: These horizontal lines represent materials, energy, or information moving through the system.
– **Nodes**: These vertical lines are where flow channels split or converge. They represent process points or transitions.
– **Labels**: These labels identify each flow channel, process name, or any relevant information.
– **Arrows**: Arrows represent the flow direction.
– **Diagrams**: The overall shape resembles a tree or a large waterway, with branches and branches of branches representing sub-processes, and a few main channels indicating how processes are linked or separated.
**How to Construct a Sankey Diagram**
Constructing a Sankey diagram involves several steps:
1. **Select the Data**: Gather the data you wish to visualise. For materials, this could be mass, volume, or the number of items. For energy, it’s typically kilowatt-hours.
2. **Define Inputs and Outputs**: Determine the starting points (inputs) and ending points (outputs) of the flow you are analysing.
3. **Identify the Process**: Break the process down into individual tasks or phases and identify where flows merge or split.
4. **Choose the Channel Width**: The width of each flow channel should represent the mass, volume, or energy of the flow.
5. **Draw the Nodes**: Represent the process steps as nodes, linking them with channels.
6. **Label**: Ensure every process and channel is clearly and accurately labeled.
7. **Visualize Losses and Diversions**: Show the loss of material or energy in the system as narrow channels diverging off main flows.
**Interpreting Sankey Diagrams**
Interpreting Sankey diagrams effectively depends on understanding the data and the flow channels. Here are some key points to consider:
– **Efficiency**: The width of the channels tends to decline upstream, indicating the loss of material or energy over time or between processes. A thin channel can mean minor material loss, but a thin channel at the start of a process could signify significant material loss.
– **Flow Splitting and Merging**: Where channels split or recombine can indicate processes of division or unification in the flow.
– **Losses**: Channels to the sides of the main flow channels could represent by-products, waste, or other losses.
**Applications in Analytical Studies**
Sankey diagrams are versatile tools with a broad range of applications:
– **Environmental Analysis**: Assessing the flow of waste materials or energy consumption in manufacturing processes.
– **Chemical Industry**: Monitoring resource use and waste generation in chemical plants.
– **Energy Studies**: Understanding energy flow patterns in power systems and the efficiency of energy conversion.
– **Urban Planning**: Illustrating the flow of waste water, air pollution, or greenhouse gas emissions in urban settings.
The use of Sankey diagrams not only makes the often-intangible or abstract concept of flow tangible but also facilitates better insights into the processes under analysis. With their high information density and clarity, these diagrams are a powerful analytical and communication tool for researchers and professionals across many fields.
As with any analytical tool, the careful planning and thoughtful construction of a Sankey diagram are key to its effectiveness. When used correctly and interpreted with a comprehensive understanding of the system in question, Sankey diagrams can provide invaluable insights into the functioning of complex systems and the flows within them.
