Piezoelectric Vibration Energy Harvesting Device Combined with Damper

Transcription

1 Vol. 2, No. 2, pp (2014) Piezoelectric Vibration Energy Harvesting Device Combined with Damper Hung-I Lu 1, Chi-Ren Yang 1, Shih-Rong Ceng 1 and Yiin-Kuen Fuh 1,* 1 Department of Mechanical Engineering, National Central University, Taoyuan, Taiwan, ROC *Corresponding Author / michaelfuh@gmail.com KEYWORDS : Piezoelectric, Vibration, Energy harvesting Piezoelectricity is a type of material that enables mechanical energy and electrical energy to be interchangeable, which can be divided into positive piezoelectric effect and inverse piezoelectric effect. The positive piezoelectric effect is that the electric dipole moment of material generates changes when the piezoelectric material is subjected to pressure, resulting in electrical energy. Conversely, the inverse piezoelectric effect is the process of electrical energy converted into mechanical energy. Manuscript received: March 13, 2014 / Accepted: March 31, Preface Rekindled research interest in piezoelectric energy harvesting devices has increased dramatically in recent years due to the advent of potential applications in wireless electronics and simple implementation of vibration based generators. A simple theoretical linear model of piezoelectric energy harvesters have been built and are widely available [1]. One of the interesting energy harvesters adopts a rotational windmill with a cantilever configuration to generate electrical charge from piezoelectric materials using the 31- mode [2]. Though simple in formulation, these models have been successfully validated with experimental measurements and surprisingly good levels of agreement have been achieved. Extending the linear modeling assumption which includes the situation of increasing excitations levels as well as nonlinearity arising in geometric and material, an interesting and an increasingly significant effect of broadband phenomenon has occurred [3-4]. Several coupling effects have been investigated such as strong nonlinear behavior under magnetic and elastic coupling interactions, to result in high amplitudes of mechanical or electrical excitation [5-6]. This paper aims to further investigate this effect by extending to the structural coupling and lithium battery recharging capability of the proposed damper-assisted piezoelectric harvester. From the basic principle of piezoelectric patches, convert the mechanical energy into electrical energy, combined with piezoelectric patches, springs and magnets mechanism to produce a piezoelectric vibration energy harvester. Then improve the general piezoelectric vibration energy harvester, apply to a damper or the vibration source, test the performance of the different pre-loads, adjust the magnet difference as well as force imposed from single, double sides and identify an optimally set piezoelectric vibration energy harvesting device. 2. Experimental device Device design: remove the suspension from a remote control car. Affix four powerful magnets. The spring can compress normally when affected by the force. After the spring rebounds to the balance point, limit the amount of pulling up. Thereby increase the effect of piezoelectric sheet and retain the original function of the damper. Then fix shock absorbers with a magnet and piezoelectric patch. Lock them on the wood block. Fix with clips on the stand. Use a vibration table corner to press unit downward, leading to deformation of the suspension and then let the piezoelectric patch be subjected to the force. Use lithium batteries to capture the vibration energy. 3. Implementation analysis (1) Firstly, in the case of different resistance values, measure the generated Vpp value as well as power and find the maximum value power. (2) Use the maximum value power to set the device to be subjected to bilateral force. Spacing between the magnets is 9mm (as Fig. 2 ). Adjust the frequency generated by the vibration table. Record once every 2Hz and identify Vpp value under the various frequencies, then find a diagram of relation between Vpp and frequency, then analyze and change different pre-loads (0mm, 2mm, 3mm, 4mm). Preload diagram is as per Fig

2 Vol. 2, No. 2, pp (2014) Pre-load is 3mm and set the frequency as 41Hz. Capacitors and lithium batteries are filled in (as Fig. 4). Measure relationships between the time and voltage. (d) Fig. 3 Mechanism action figure Mechanism action front view pre-load, black dashed line 0mm, blue: 2mm, Red: 3mm, Green: 4mm, based on fixed end of piezoelectric patch the distance under the pre-pressure (Schematic diagram of Fig. 1 ) (e) Fig. 1 A device is set up Front view Side view Layout (d) The whole experiment figure (e) Layout schematic diagram Fig. 4 Charging circuit diagram Zener diode and capacitors are added respectively in order to reduce and stabilize the voltage at 3.8V. You can charge and increase the life expectancy of the lithium batteries. 4. Results and discussion (1) Resistance performance analysis Fig. 2 Different settings (Schematic diagram of Fig. 1 ) (3) Change into withstanding bilateral force. The spacing between magnets is 13mm (as Fig 2 ), that is, change the distance of the magnets, and repeat step (2). (4) Change into withstanding unilateral force. The spacing between magnets is 9mm (as shown in Fig 2 ). Namely, only a unilateral action of the spring and magnets remains, and then repeat step (2). (5) Withstand bilateral force. Spacing between magnets is 9mm. 97

3 Vol. 2, No. 2, pp (2014) Fig. 5 At a fixed vibration frequency of 41Hz measures change in different resistance values Vpp-resistance figure Power-resistance figure Results: It can be seen from the Fig. 5 that when the resistance is 39kΩ, the value of the measured power is 3.8mW, the maximum value, so all the follow-up experimental resistance uses 39kΩ. (2) Pre-load analysis Results: When it is subjected to bilateral force and the distance between the magnets is 9mm, a maximum value comes to pass at 42Hz. And when pre-load is 3mm, there is a maximum value of 48V. When it is subjected to bilateral force and the distance between the magnets is 13mm, there is a maximum value generated at 40Hz. And when pre-load is 3mm, there is the maximum value of 30V. When it is subjected to unilateral force and the distance between the magnets is 9mm, there is a maximum value generated at 38Hz. And when pre-load is 2mm, there is the maximum value of 32.4V. When it is subjected to bilateral force, the distance between the magnets is 9mm, preload is 3mm, vibration frequency is between 30 and 50Hz, Vpp is 20V or more, and there is the maximum Vpp 48V at 42Hz, it has the best performance of all data made. It is inferred that when the magnet force is large, efficiency would be better, and efficiency from being subjected to bilateral force will be higher than being subjected to unilateral force. Fig. 6 Vpp-frequency affected by bilateral force. Spacing between the magnets is 9mm. affected by bilateral force. Spacing between the magnets is 13mm. affected by unilateral force. The distancebetween the magnets is 9mm. (3) Recharge lithium battery According to the previous data, under the condition of being subjected to bilateral force, when spacing between magnets is 9mm, pre-load is 3mm, the frequency between 40 and 50Hz has maximum energy efficiency, which can be used to convert to the charging energy, to find the best charging efficiency. Conclusion: recharge with stable voltage 3.8V. When the lithium battery just starts charging, voltage rises fastest, but after that the rate will rise more and more slowly. Start charging from 2.72V. After charging 48 minutes, it reaches 2.94 V. When charging capacity, use the horizontal axis in Figure, 5 seconds per frame. Therefore it just takes approx. 10 seconds to enable the capacitor to charge from 0V to 28V. 98

4 Vol. 2, No. 2, pp (2014) Fig. 7 It is subjected to bilateral force. Spacing between magnets is 9mm. Frequency is 41Hz. the time and voltage for recharging lithium battery figure 36μF capacitor is filled in. Relation between time and voltage diagram (not connected with Zener diode) 5. Conclusion piezoelectricity. That is, the Vpp value of a piezoelectric patch directly affected by a force within a specific frequency range is smaller than a piezoelectric patch fitted with this unit. When affected by a bilateral force, spacing of the magnets is 9mm, and preload is 3mm, there is a maximum value of Vpp. And in the meantime the impact of the pre-load size on the frequency and voltage is maximal. There are many machines in life whose unnecessary energy consumption comes into being on account of vibration. In order to recover the waste energy and reduce into usable energy, we use a piezoelectric material to convert the vibration energy into electrical energy, and by use of a lithium battery, store the electrical energy for usage, which can be used on the machines of specific frequency ranges. For instance: most bicycles and motorcycles have shock absorbers. It can be used to enhance the effectiveness of the suspension. When an existing shock absorber confronts vibration, its energy turns into heat energy and is lost. Make use of similar devices so that the energy of vibration turns into electrical energy, which can be applied to supply wireless sensors such as: tire pressure sensors, brake warning devices to avoid brake failure, or bicycle lights. Fig. 9 Concept map of link with shock absorbers. Device mounted on a bicycle shock absorber in front to capture energy from vibration during riding. Fig. 8 Vpp-frequency plot comparison between the direct piezoelectricity and settings of 9mm magnets distance with 3mm preload comparison of the maximum values of Vpp in different settings in the different pre-loads The results: Vpp value resulting from piezoelectric energy harvester plus shock absorbers between 35Hz-50Hz is larger than direct There is still room for improvement on the efficiency of the current piezoelectric patch. If in the future the efficiency can be increased, application to shock absorbers or suspension devices will be able to more effectively capture the energy of vibration and life expectancy of piezoelectricity can effectively raise owing to the shock absorber effect. While in terms of the charging circuit, various electronic components consume power, so in order to have a higher charging efficiency, single voltage controllable parts should be used. For example: control of IC by direct use of the charge not only can increase the power of a lithium battery obtained in itself, it can also increase battery life. 99

5 Vol. 2, No. 2, pp (2014) ACKNOWLEDGEMENT This thesis was completed jointly by three special project students of the Department of Mechanical Engineering, National Central University. Professor Fuh Yiin-Kuen and laboratory seniors supported us and provided laboratory equipment and locations, so that the paper could be successfully completed; we hereby express our gratitude. REFERENCES [1] S. Roundy, P. K. Wright, A piezoelectric vibration based generator for wireless electronics Smart Materials and Structures, 13, (2004) DOI: / /13/5/018 [2] S. Priya, Modeling of electric energy harvesting using piezoelectric windmill Applied Physics Letters, 87, (2005) DOI: / [3] Y. Zhu, J. Zu, and W. Su, Broadband energy harvesting through a piezoelectric beam subjected to dynamic compressive loading Smart Materials and Structures, 22, (2013) DOI: / /22/4/ [4] S. Zhou, J. Cao, A. Erturk, and J. Lin, Enhanced broadband piezoelectric energy harvesting using rotatable magnets Applied Physics Letters, 102, (2013) DOI: / [5] L. Tang, Y. Yang, A nonlinear piezoelectric energy harvester with magnetic oscillator Applied Physics Letters, 101, (2012) DOI: / [6] C. I. Kim, Y. H. Jang, Y. H. Jeong, Y. J. Lee, J. H. Cho, J. H. Paik, and S. Nahm, Performance Enhancement of Elastic- Spring-Supported Piezoelctric Cantilever Generator by a 2- Degree-of-Freedom System Applied Physics Letters, 5, (2012) DOI: /APEX