Energy flow diagrams

Diagrams can be used to show how energy is transferred from one store to another. Two examples are the transfer diagram and the Sankey diagram.

Transfer diagrams

In transfer diagrams the boxes show the energy stores and the arrows show the energy transfers.

For example, a transfer diagram for a child at the top of a slide may be:

Energy transfer diagram of a child on a slide

Gravitational energy stored in the child at the top of the slide is transferred as mechanical work done to speed up and to do work against friction. The result of this is a shift of energy from the gravitational potential energy store to the kinetic energy store and the internal energy store (raising the temperature of the child and the slide).

Sankey diagrams

Sankey diagrams start off as one arrow that splits into two or more points. This shows how all the energy in a system is transferred into different stores.

Sankey diagram of a child on a slide

Sankey diagrams are really useful when the amount of energy in each of the energy sources is known. The width of the arrow is drawn to scale to show the amount of energy.