Piezoelectric devices for ocean energy: a brief survey
J. Ocean Eng. Mar. Energy
Piezoelectric devices for ocean energy: a brief survey
Abdulrahman Jbaily
Ronald W. Yeung
Piezoelectric materials directly convert strain energy into electric energy and vice versa and are commonly used in sensing and actuating applications. They have been employed in mediums frequently undergoing vibrations, allowing harnessing of power at a small scale. Ideas of using the piezoelectric effect as a power take-off mechanism for ocean energy emerged in the 1970s and are still at a developing stage. This article overviews recent development on the application of the piezoelectric processes to the ocean field and provides a building block for future research work of ocean engineers who are interested in such possibilities. A brief discussion on the selection of the piezoelectric materials for different ocean-engineering applications is presented. Significant research projects on ocean-energy extraction through the use of these materials are then described and discussed with special scrutiny on the viability of proposed designs and their experimental or numerical validation. Various harvesting techniques in an ocean environment are categorized and compared. The challenges ahead and the outlook for success in this area are outlined.
Piezoelectricity; Ocean engineering; Energy harvesting; Piezoelectric materials; Energy scavenging; Waves; Electromechanical coupling
1 Introduction
Many large-scale technologies have been developed over the
years to capture renewable energy. These include wind
turbines, photovoltaic power plants, geothermal power stations,
among others. Still, as shown in Fig. 1,1 in the USA as
an example, only 9 % of the energy consumption in 2012
was attributed to renewable sources
(Energy Worldnet 2013)
.
Further, while many of the land-based technologies are
maturing, those involved in the marine environment are just
emerging. The low percentage in renewable-energy sources
is associated with the high cost of extraction technologies and
the unavailability of the resources during all times of the year.
Extensive research is continually being conducted to enhance
the feasibility and usage of these large-scale efforts. In fact,
it is expected that by 2040
(Institute For Energy Research
2012)
, the share of the fossil fuels will decrease by 4 % along
with a 4 % increase in renewable-energy shares.
Besides the large-scale energy sources, smaller-scale
energy sources that would end up being wasted and unused
are abundant. They are in the surroundings, such as vibrating
machines, shock absorbers, and flow turbulence
(Priya 2007)
.
Such ambient energy, if captured and transformed into
useful electrical energy, can power nearby electronic equipment.
Although such power sources provide only a small amount
of power, they can be vital in many applications, particularly
those involving self-powered devices.
Among the different types of available ambient-energy
sources explained in
(Nechibvute et al. 2012)
, vibrational
energy is the most attractive one because of its abundance
and easy accessibility. It is kinetic energy that can be
converted into electric energy using piezoelectric,
electromagnetic, or electrostatic principles. Piezoelectric transducers,
being smaller and lighter, are usually favored over the other
1 Note from reference: sum of components in Fig. 1 may not equal
100 % because of independent rounding. Source of component values:
US Energy Information Administration, Monthly Energy Review, Table
1.3 and 10.1 (April 2013), preliminary 2012 data.
Solar 2%
Geothermal 3%
means. They also have energy generation density that is three
times higher
(Priya 2007)
. Also, piezoelectric materials can
be easily integrated into a system, having no moving parts,
thus not requiring frequent maintenance. Further, they have
the favorable ability of directly converting applied strain
energy into electric energy, and producing power at voltage
levels that can be easily conditioned
(Nechibvute et al. 2012)
.
Power harvesting through piezoelectricity
(Erturk and
Inman 2011)
is emerging as one of the most
important ambient-energy scavenging methods. The scavenging
devices are traditionally embedded in a vibrating host
structure that can endure substantial excitations. Recent research,
however, is directed to media that have prevalent
fluctuations themselves.
Priya et al. (2005)
, for example, developed
a piezoelectric windmill to extract the energy from wind
currents. The mill consists of piezoelectric bimorph cantilevers
that are arranged along its circumference. The design makes
use of the camshaft gear mechanism to induce oscillations
on the piezoelectric patches, and hence generates power.2
In this survey article, we review the harvesting of ocean
energy using piezoelectric materials. The questions of
interest are:
What are the applications? What are the viable designs? What
is the order of magnitude of the power output? What are the
challenges in such develop (...truncated)