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timothykinney's avatar

What is the most efficient kinetic energy conversion?

Asked by timothykinney (2730 points ) January 28th, 2009

I am curious what the most efficiency way to convert kinetic energy into electrical energy is (known to man). This means not using heat (cogeneration) or potential energy (hydroelectric). But just turning motion into electricity (faraday effect, brakes on a Prius, etc.).

Can someone point to a source that gives a percentage conversion higher than 75%?

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7 Answers

Harp's avatar

It’s generally considered that the theoretical efficiency limit of any system is described by the Carnot Cycle. The most promising new technologies, which convert heat directly to electricity, have Carnot limits somewhere around 77%, though that is unlikely to be achieved in practice.

Harp's avatar

Oops, I see I didn’t read the Q carefully enough. I did find this paper, however, that proposes using convection currents in a closed cycle as an extremely efficient generation source that sort of sidesteps the Carnot limit.

gailcalled's avatar

So Milo on a treadmill won’t cut it?

Harp's avatar

Only ‘til he figures out he’s being “useful”. Violates the feline code of honor

Harp's avatar

New energy unit: the “Milowatt”

Sorceren's avatar

I’m no math or physics whiz, but does piezoelectricity count? There’s a material out there from a Cerametrics company that creates energy when flexed: Harvestor. Someone wants to use it in factory flooring; they would gather enough energy from foot-strikes to be the sole power sending wireless signals to the factory’s external surveillance system.

It offers: ►10X more power than ceramic piezospiezos►Eliminate battery replacement
►Tested to over 1 billion cycles with virtually no output degradation.►Convert up to 70% of energy from ambient vibration to electrical power►Most efficient transducer material available today; Most piezoelectric active fibers

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