August 14, 2011

4.5 Sankey Diagrams

Describe a variety of everyday and scientific devices and situations, explaining the fate of the input energy in terms of the previous relationship [see 4.4], including their representation by Sankey Diagrams.

In laymen's terms: Use a Sanky diagram (shown below) to explain how input energy is divided into "waste" and "useful" energy.

Filament Light bulb
The diagram above is a simple 'Sankey Diagram' it shows that when 100J of electrical energy is put into (in this case) a filament light bulb, only 10J is released as useful light energy and the remaining 90J is lost as heat. Using the previous relationship [from 4.4] we can see that:

$E = 0.1 = 10\%$

So a filament light bulb has an efficiency of 10%

Energy Saving light bulb

On the other hand the Sankey diagram above for a energy saving light bulb shows that out of 100J of electrical energy only 25J is lost, meaning that an energy saving bulb is 75% efficient which is much more efficient than a filament bulb