Proceedings Article | 30 March 2012
KEYWORDS: Semiconducting wafers, Ferroelectric materials, Energy harvesting, Sensors, Transducers, Smart structures, Manufacturing, Amplifiers, Wind energy, Electronics
In recent years there has been a strong emphasis on kinetic (vibration) energy harvesting using smart structure
technology. This emphasis has been driven in large part by industry demand for powering sensors and wireless telemetry
of sensor data in places into which running power and data cables is difficult or impossible. Common examples are
helicopter drive shafts and other rotating equipment. In many instances, available space in these locations is highly
limited, resulting in a trend for miniaturization of kinetic energy harvesters. While in some cases size limitations are
dominant, in other cases large and even very large harvesters are possible and even desirable since they may produce
significantly more power. Examples of large-scale energy harvesting include geomatics, which is the discipline of
gathering, storing, processing, and delivering spatially referenced information on vast scales. Geomatics relies on suites
of various sensors and imaging devices such as meteorological sensors, seismographs, high-resolution cameras, and
LiDAR's. These devices may be stationed for prolonged periods of time in remote and poorly accessible areas and are
required to operate continuously over prolonged periods of time. In other cases, sensing and imaging equipment may be
mounted on land, sea, or airborne platforms and expected to operate for many hours on its own power. Providing power
to this equipment constitutes a technological challenge. Other cases may include commercial buildings, unmanned
powered gliders and more. Large scale kinetic energy harvesting thus constitutes a paradigm shift in the approach to
kinetic energy harvesting as a whole and as often happens it poses its own unique technological challenges. Primarily
these challenges fall into two categories: the cost-effective manufacturing of large and very large scale transducing
elements based on smart structure technology and the continuous optimization (tuning) of these transducers for various
operating conditions. Current research proposes the simultaneous solution of both of the aforementioned challenges via
the use of specialized technology for the incorporation of large numbers of piezoelectric transducers into standard printed
circuit boards and the continuous control of structural resonance via the application of adaptive compressive stress. Used
together, these technologies allow for fully scalable and tunable kinetic energy harvesting. Since the design is modular in
nature and a typical size of a single module can easily reach dimensions of 60 by 40 centimeters, there is virtually no
upper limit on the size of the harvester other than the limits that derive from its specific applications and placement. The
use of compressive forces rather than the commonly used non-structural mass for the tuning of the harvester frequency to
the disturbing frequency allows for continuous adaptive tuning while at the same time avoiding the undesirable vibration
damping effects of non-structural mass. A proof of concept large-scale harvester capable of manual compressive force
tuning was built as part of the current study and preliminary tests were conducted. The tests validate the proposed
approach showing power generation on the order of 10 mW at disturbing frequencies between 10 and 100 Hz, with RMS
voltages reaching over 20 volts and RMS currents over 2 mA, with proven potential for 50 mW with over 100 VAC and
10 mA for a transducing panel 20 by 10 cm. The results also validate the tuning via compressive force approach,
showing strong dependence of energy harvesting efficiency on the compressive force applied to the transducing panel.
