Distinguished Scholar-Teacher Lecture
Amr M. Baz, Ph.D.
Minta Martin Professor
Keystone Professor
Director, Smart Materials and Structures Research Center
Thermoacoustic Energy Harvesting
November 2, 2015 | 1:00 PM | DeWalt Seminar Room, 2164 Martin
abstract: Thermoacoustic energy conversion is an emergent technology with a considerable potential for
research, development, and innovation. In thermoacoustic resonators, self-excited acoustic oscillations are
induced in a working gas by means of a temperature gradient across a porous body and vice versa with no need
of moving parts. In the first part of this dissertation, thermoacoustic resonators are integrated with piezoelectric membranes to create a new class of energy harvesters. The incident acoustic waves impinge on a piezo-diaphragm located at one end of the thermoacoustic-piezoelectric (TAP) resonator to generate an electrical power
output. The TAP design is enhanced by appending the resonator with an elastic structure aimed at enhancing
the strain experienced by the piezo-element to magnify the electric energy produced for the same input acoustic power. An analytical approach to model the thermal, acoustical, mechanical and electrical domains of the
developed harvester is introduced and optimized. The performance of the harvesters is compared with experimental data obtained from an in-house built prototype with similar dimensions. In an attempt to further understand the dynamics and transient behavior of the excited waves in the presence of piezoelectric coupling, a
novel approach to compute and accurately predict critical temperature gradients that onset the acoustic waves
is discussed. The developed model encompasses tools from electric circuit analogy of the lumped acoustical
and mechanical components to unify the modeling domain. In the second part of the dissertation, piezo-driven
thermoacoustic refrigerators (PDTARs) are presented. The PDTARs rely on the inverse thermoacoustic effect for
their operation. A high amplitude pressure wave in a working medium is used to create a temperature gradient
across the ends of a porous body located in an acoustic resonator. Finally, PDTARs with dynamic magnifiers are
introduced. The developed design is shown, theoretically and experimentally, as capable of potentially enhancing the cooling effect of PDTARs by increasing the temperature gradient created across the porous body.
Professor Amr Baz joined the Department of Mechanical Engineering at the University of Maryland in
1997. He is a Minta Martin and Keystone Professor within in the Department, and serves as the director of
the Smart Materials and Structures Research Center. Baz is a life fellow of American Society of Mechanical
Engineers (ASME) and an associate fellow of the American Insitute of Aeronautics & Astronautics (AIAA). His
research interests include active and passive control of vibration and noise, active constrained layer damping,
magnetic composites, virtual reality design of smart structures and active acoustic metamaterials.
bio:
www.enme.umd.edu/seminars