Optimization Of The Mechanism Used For Piezoelectric Energy Harvesting

Energy harvesting devices scavenge the ambient energy to power portable electronics or wireless sensor nodes, without the use of traditional batteries, which have limited lifespan. Harvesting energy from ambient vibrations has wide potential application, and has recently attracted much attention. There are three main approaches that can be used to scavenge vibration energy: piezoelectric, electromagnetic and electrostatic. Piezoelectric generators employ the piezoelectric effect, convert mechanical energy to electrical energy directly, and are the simplest type of generator to fabricate. Piezoelectric materials are widely available and particularly well suited to micro-engineering.Performance of piezoelectric energy harvesting systems is affected by many factors: geometric parameters, vibration frequency, energy harvesting circuitry and properties of the piezoelectric material. The systems are optimized to scavenge more energy per volume of piezoelectric material. The ways to maximize the piezoelectric response for a given input include the design of efficient harvesting geometries, improving efficiency through circuitry.Cantilever beam is a common configuration in energy harvesting systems. It is concluded theoretically that the electrical energy stored in the piezoelectric element is proportional to the square of the strain integral. Uniform strain distribution is desirable to fully utilize the potential energy in piezoelectric material. Traditional beam has constant cross-section, its surface strain decreases linearly in the length direction. The electrical energy stored in the piezoelectric element attached to the uniform-strain beam will be 4 times that with the traditional beam, when their maximum strain is the same. A cantilever beam with non-constant thickness is a favorable uniform-strain structure. An approximate uniform-strain beam was fabricated by bonding several steel sheets together. Moreover, a Macro Fiber Composite (MFC) was attached on it and used as the electricity generator. It has been proven experimentally that the electrical energy generated by the approximate uniform-strain system has been increased by a factor of 2.04 as compared to the uniform cross-section system.