Digital Object Identifier: 10.11 09IULTSYM.2008.0253
Jet Propulsion Laboratory, California Institute ofTechnology
4800 Oak Grove, Pasadena, CA, 91109
transformation of acoustic vibrations into electrical energy are
systems. Typically these applications involve extracting energy at
remote or isolated locations where local long term power is
unavailable or inside sealed or rotating systems where cabling
acoustic power spectra can
be in the form
transverse, bending, hydrostatic or shear waves of frequencies
less than a Hz to 10's of kHz.
stress/vibration power can be generated by machines, humans or
We will present a variety of acoustic energy harvesting
modes/devices and look at the commonalities of these devices.
The common elements of these systems are: an input mechanical
power spectrum, an effective acoustic impedance matching, a
conversion of the input mechanical energy into electrical energy
using piezoelectric or biased electrostrictive transducers and a
matched electrical load.
This paper will focus of the physical
acoustics of these energy harvesting systems and identify the
elements of these devices and look at the current limits of the
harvested electrical power from these devices.
Recent results on
an acoustic electric feed-through device demonstrated acoustic
power conversions of the order of 70 W/cm
and 25 W/cm
a pre-stressed stacked PZT ceramics operating at 16 kHz with an
efficiency of 84
These results suggest the piezoelectric is not
the limiting element of these devices and we will show that the
main impediment to increased power is the vibration source
amplitude, frequency, inertia and the size limitations of the
energy harvesting systems or in the case of human powered
systems the requirement that the device remains unobtrusive.
Although the power densities of these devices may be limited
there are plenty of applications that are feasible within the
available power densities due to the wonders of CMOS.
Keywords: Piezoelectric Transduction, Energy Harvesting, Energy
Scavenging, Active Damping, Autonomous sensing
developed using piezoelectric energy harvesting transducers
technologies[l ,2,3,4,5]. These systems convert various forms
of mechanical vibrations into AC electrical signals which can
be conditioned[5,6,7,8] to supply DC power to a load or
harvesting using the piezoelectric effect is the solar cell.