An Optimization of Energy Harvesting Techniques through Mechanical Vibration
Energy harvesting through mechanical vibration have emerged as an important research area and continues to grow at rapid pace. A wide range of applications are targeted for the harvesters, including distributed wireless sensor nodes for structural health monitoring, embedded and implanted sensor nodes for medical applications, recharging the battery of large systems, monitoring the tyre pressure in automobiles and running security system in household conditions. Several transduction mechanisms exist for transformation of mechanical energy of mechanical vibrations into electric energy. Principle of vibration energy harvesters is in most cases mass-spring-damper system with one degree of freedom. Considering physical principles used to transform kinetic energy into electrical energy, there are four transduction mechanisms: electrostatic, piezoelectric, electromagnetic and magnetostrictive
One latest and good example of energy-harvester device is “Mechanical motion rectifier”. It is based on electromagnetic principle and the key component is a unique motion mechanism, which is called “mechanical motion rectifier (MMR)”, to convert the oscillatory vibration into unidirectional rotation of the generator. The prototype achieved over 60% efficiency at high frequency, much better than the conventional regenerative shock absorbers in oscillatory motion. Furthermore, road tests are done to demonstrate the feasibility of the MMR shock absorber, in which more than 15 Watts of electricity is harvested while driving at 15 mph on a smooth paved road. The motion rectifier based design can also be used for other applications of vibration energy harvesting such as from tall buildings or long bridges.
One another good example is harvesting vibration energy by a triple-cantilever based on triboelectric nanogenerator. Triboelectric nano-generators (TENG), a unique technology forharvesting ambient mechanical energy based on triboelectric effect, have been proven to be acost-effective, simple and robust approach for self-powered systems. TENG produces an open-circuit voltage up to 101 V and a short-circuit current of 55.7 μA with a peak power density of 252.3 mW/m2.