Sankey Diagrams

Why are they called Sankey Diagrams?

Captain Henry Sankey (1853 – 1925)

Captain Matthew Henry Phineas Riall Sankey was an engineer.

In 1898 he was the first person to publish a diagram that used the width of an arrow to show the size of the energy flow.

The first ever Sankey diagram shows the energy flow in a real steam engine compared with a ‘perfect’ engine.

10 J energy in

1 J

useful

energy

out

9 J

wasted

energy

out

Sankey Diagram for a filament bulb

10 J energy in

1 J

useful

energy

out

9 J

wasted

energy

out

10 J energy in

4 J

useful

energy

out

Sankey Diagram for a filament bulb

Sankey Diagram for an energy efficient bulb

6 J

wasted

energy

out