Tuesday, February 5, 2008

Transport Efficiency

Energy consumption is costly and steadily increasing today. A majority of production and consumer buying decisions are based around efficiency of the product they are designing or purchasing. With this in mind, it will be nice to have the moving transportation system in question have as little dead weight as possible and more payload weight instead.

Dead weight, denoted by Wempty, like dead load in structures, is non-productive and costs money to move around during its economic life.

Payload is the part of the transportation system, other than structural items, that will gain something (like humans moving from one position to another) or it will generate money for some other public party. Weight of the payload is denoted by Wpayload.

When considering the Wempty/Wpayload ratio, interesting results are observed. This ratio is a dimensionless paramter by which we can have some amount of idea of transport efficiency. Generally, we want this ratio to be as small as made possible with the resources we have.

An ant can carry around, in extreme cases, more than 5 times its own body weight. Therefore, 1/5 = 0.2! Which is pretty low and excellent. But rarely is an ant important to us, nor can it carry us around. (I was thinking about trying ;) )

A bicycle, with an average weight of 20 pounds (not really a performance centered bike but a normal commuter one), can easily lift and transport weights in excess of 180 lbs. 20/180 = 0.1 (average)!

Plus, it does not consume an ounce of non-renewable fuel!

Think about all the vehicles you can find on the road or rail, underwater, in air, and in space. I'm not really sure if anything comes close to the bicycle.

A tabulation from Adrian Beukers paper (Page 4) confirms this. See below.


RobiNZ said...

Ummm, I'm a cyclist and a motorist but you're dreaming if you think;

"...it does not consume an ounce of non-renewable fuel!"

Bikes are made from steel, alloy, carbon. plastic whatever and none of that stuff appears out of think air without energy being consumed.

I presume most cyclists don't grow all their fuel, food, at home. Everything they eat is the result of a, sometimes long and petroleum dense, production and distribution process.

Bikes are very efficient but still need their fair share of non-renwable engery to run.

Robinz said...

It came to mind as recently read of a "total lifecycle study" which rated a Prius worse than a Hummer. The reason was the exotic materials (exotic alloys/plastics) and short operating life vs crude materials (steel) and longer operating life.
It would be interesting to see a total lifecycle study for a modern bike! Would be far better than a car for sure but maybe not a green as you'd think.

I know the operating costs can be higher as my spend on "café rides" is more $/km than the car consumes :-)