Environmental Engineering Reference
In-Depth Information
Input Force
Tensile
Force
+
-
Harvested
Voltage
FIGURE 4.15
A diagram of the prestressed piezoelectric diaphragm material, TH7R.
As an input force is applied at the centre of the warped structure dome-
shaped piezoelectric strip, a resultant tensile force is generated in the piezo-
electric material along the 1-axis and voltage is harvested and poled along
the 3-axis, as illustrated in
Figure 4.15
. Unlike the piezoelectric igniter that
operates in the parallel compression mode or 33-mode of operation, this trans-
verse configuration maximizes the piezoelectric transducer efficiency in con-
verting mechanical energy to electrical energy in a low-force environment.
The innovative part of this research is the use of the natural characteristic and
construction of the prestressed diaphragm material as an energy harvesting
material (its unique characteristic is that when the material is depressed, it
is deformed, and it generates electrical energy) as well as a switch (its pre-
stressed construction creates a bouncing reaction whenever the material is
depressed at the centre).
Referring to
Figure 4.16
, the THUNDER piezoelectric device consists of
a piezoelectric ceramic layer, PZT, and a backing metal layer, held together
with a polyimide adhesive as described by Bryant [117]. Several researchers
have investigated this type of device, and literature is widely available on
its actuation and manufacturing details. However, very few researchers have
examined its potential as an energy conversion mechanism [118]. As an en-
ergy harvesting device, few publications are available: Ramsay et al. [54]
demonstrated the feasibility of utilizing the power generated in a bio-MEMS
(bio-microelectromechanical system) application; Mossi et al. [119] compared
different configurations of the device for actuation and energy harvesting;
and Shenck et al. [46] utilized this device for harvesting energy by mounting
Metal Top Aluminum
Adhesive (Polyimide)
Piezoelectric (PZT)
Adhesive (Polyimide)
Metal Substrate Stainless Steel
FIGURE 4.16
Construction of a THUNDER TH7R.
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