World Energy: Where It Comes From, Where It Goes

I admit it: I have a weakness for Sankey diagrams--a kind of directional flow chart, says the Chemical Engineering blog, "where the width of the streams is proportional to the quantity of flow, and where the flows can be combined, split and traced through a series of events or stages." They even have their own blog, at Sankey Diagrams ("A Sankey diagram says more than 1000 pie charts"). They turn out to be exceptionally well suited to representing energy flows--witness the example below, by Cullen and Allwood, of world energy use. (Click for larger image.)

 
Here's how to unpack it. The leftmost bar shows energy sources. The second is clear enough: the direct use to which that fuel is put. The middle bar is another way of envisioning the conversion of the energy in the first bar, this time to motion, heat, or light. Fourth shows where the energy goes--to vehicles, factories, and buildings. Finally, the rightmost bar sums up the eight major fields to which energy is put--a few joules of which you're reading right now. Our task: Increase the size of that blue line for Renewables.

--Paul Rauber