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Directory:Acoustic

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Technologies

Thermoacoustics

See Directory:Thermoacoustics

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Other Acoustic Technologies

  • A Sound Way to Turn Heat into Electricity - University of Utah physicists developed small devices that turn heat into sound and then into electricity via piezoelectric conversion. The technology holds promise for changing waste heat into electricity, harnessing solar energy and cooling computers and radars. (PESN; May 5, 2007)
  • Los Alamos National Laboratory has developed an "Acoustic Stirling Heat Engine" with no moving parts. It converts heat into intense acoustic power. [1]
  • Acoustic Propulsion - Two spherical Helmholtz resonators (glass Christmas tree bulb ornaments with a resonance frequency of 386 Hz) connected by a thin rod and suspended from a thread will rotate when driven at their resonance frequency, provided that the driving sound is loud enough (in this case more than 125 dB). (Free Energy Blog; November 11, 2013)

Comments

Increased Efficiency Losses

On June 17, 2007, NEC advisor, Jim Dunn wrote:

To first convert heat to sound and then sound to electrical energy will not yield over 12-15% efficiency, which is where we are with peltier and Seebeck devices today.

Heat to sound is not simple or efficient, (20-30%) and sound to electric (as in piezoelectric or capacitive (electret) microphones) is quite mature, but not considered of good efficiency (25-35%). Other possible choices like Barium titanate transducers might be a little better, but still not dramatic.

To compound 2 low efficiency devices (20-30% each) will not yield over 10% final net efficiency.

This is not likely to beat existing techs.

Rebuttal

On June 21, 2007, Ken Rauen wrote:

I beg to differ. See http://www.lanl.gov/mst/engine/

The Los Alamos National Laboratory team that developed the first practical acoustic Stirling engine now has its efficiency up to 30%. They say linear motor/generators can be driven by this engine, and such generators are over 80% efficient. 30% x 80% = 24%. A 90% alternator would make it 27%. These are much better numbers than James Dunn claims they are.

I say thermoacoustic engines with linear alternators are more efficient than common thermoelectric generators. They are about the same in cutting edge TEG designs which are reported to be about 25% efficient.

For those of you who do not know, Peltier and Seebeck devices are the same thing! They are thermoelectric devices such as thermocouples, thermopiles, and thermoelectric generators. The Peltier effect is the phenomenon of heat-to-electricity and electricity-to-heat at a thermoelectric junction, such as a p-n junction in semiconducting materials; a solar cell exhibits the same thing with a particular wavelength of light. The Seebeck effect is the voltage of said junction, as a function of temperature, measured in volts per degree.

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Topic Specialist: Vladi S. Travkin‎

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