Ambient Sound Energy Harvesting

[drew hempel]

On energy harvesting from ambient vibration

Author(s): Stephen NG
Source: JOURNAL OF SOUND AND VIBRATION Volume: 293 Issue: 1-2 Pages: 409-425 Published: MAY 30 2006
Times Cited: 14 References: 14

Abstract: Future MEMS devices will harvest energy from their environment. One can envisage an autonomous condition monitoring vibration sensor being powered by that same vibration, and transmitting data over a wireless link; inaccessible or hostile environments are obvious areas of application. The base excitation of an elastically mounted magnetic seismic mass moving past a coil, considered previously by several authors, is analysed in detail. The amplitude of the seismic mass is limited in any practical device and this, together with the magnitude and frequency of the excitation define the maximum power that can be extracted from the environment. The overall damping coefficient (part of which is mechanical) is associated with the harvesting and dissipation of energy and also the transfer of energy from the vibrating base into the system. It is shown that net energy flow from the base through the damper is positive (negative) for omega >omega(n) (omega <omega(n)), but is zero when omega=omega(n). The mechanical part of the damper cannot contribute more power than it dissipates and is neutral, at best, when omega/omega(n) -> infinity. Maximum power is delivered to an electrical load when its resistance is equal to the sum of the coil internal resistance and the electrical analogue of the mechanical damping coefficient, which differs from what has been claimed. A highly damped system has the advantage of harvesting energy over a wider band of excitation frequencies on either side of the natural frequency, is smaller, but will harvest marginally less power. One possible strategy for variable amplitude excitation is proposed. © 2005 Elsevier Ltd. All rights reserved.
Document Type: Article
Language: English
KeyWords Plus: GENERATOR; SYSTEMS
Reprint Address: Stephen, NG (reprint author), Univ Southampton, Sch Engn Sci Mech Engn, Southampton SO17 1BJ, Hants England
Addresses:
1. Univ Southampton, Sch Engn Sci Mech Engn, Southampton SO17 1BJ, Hants England

[psilocybin]

I believe this technology was first developed by the KGB to make non locatable bugs. I remember reading something about a scientist in russia that was "genius" enough to use the sound energy to affect movement to create a current.

[drew hempel]

Science Daily this week has "Controlling Light with Sound" -- excerpt:

To do this, his new method couples two droplets of water through a cylindrical hole. When exposed to certain frequencies of sound, the device exploits inertia and water’s natural surface tension and becomes an oscillator, or something akin to a small pendulum: the water droplets resonate back and forth with great speed and a spring-like force. Researchers can control the rate of these oscillations by exposing the droplets to different sound frequencies.

By passing light through these droplets, the device is transformed into a miniature camera lens. As the water droplets move back and forth through the cylinder, the lens moves in and out of focus, depending on how close it is to the object. The images are captured electronically, and software can be used to automatically edit out any unfocused frames, leaving the user with a stream of clear, focused video.

“The great benefit of this new device is that you can create a new optical system from a liquid lens and a small speaker,” Hirsa said. “No one has done this before.”