# Energy Resources and Transfer: Sankey Diagrams

## Energy Resources and Transfer: Sankey Diagrams

- Sankey diagrams are graphical representations that illustrate the energy flow in a system.
- The thickness of the arrows in a Sankey diagram is directly proportional to the amount of energy they represent.
- In these diagrams, the length of the arrows is immaterial - only their width matters.
- A Sankey diagram always starts with one arrow—the input, which usually represents 100% of the energy.
- The energy input arrow branches off into different arrows, each symbolising the destination or path of the energy.
- Some energy paths represent useful outcomes (useful energy), such as the mechanical act of moving a car.
- Other energy paths represent wasteful or unintended outcomes (wasted energy), like heat lost from a car engine.
- Energy cannot be created or destroyed, only transferred or stored. Therefore, the total width of all output arrows from the system must equal the width of the input arrow, reinforcing the principle of conservation of energy.
- The more efficient a system is, the greater the proportion of energy represented by the useful outcome arrow.
- To calculate energy efficiency using a Sankey diagram, divide the useful energy outcome by the total energy input, then multiplying by 100 to convert to a percentage.
- Sankey diagrams can be used to visually compare the efficiency of different systems or investigate changes in efficiency under different conditions.
- A system with a big wasteful energy arrow indicates low efficiency and suggests an area for potential improvement.
- Understanding Sankey diagrams helps in getting a comprehensive understanding of Energy Resources and Energy Transfer, critical in sectors like power generation and transport.
- It is important to use correct units when working with these diagrams, commonly the units are either joules (J) or watts (W), depending on whether the energy is being considered over time.