HUMAN LOCOMOTION VIBRA-E (VIBRATIONAL ENERGY) HARVESTER PROTOTYPE FOR POWERING LIGHT EMITTING DIODE

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1 APEC Youth Scientist Journal Vol.7 / No.2 HUMAN LOCOMOTION VIBRA-E (VIBRATIONAL ENERGY) HARVESTER PROTOTYPE FOR POWERING LIGHT EMITTING DIODE Reisha Claffel Z. Ferraren 1, Peter Gabriel A. Muaña 1 1 Philippine Science High School Central Visayas Campus, Talaytay, Argao, Cebu, PHILIPPINES ABSTRACT With the global energy crisis, many technologies in energy harvesting, such as solar, wind, geothermal, and hydraulic power plants, have been developed. This project envisioned to explore the potential of vibrations as a sustainable alternative source of energy through a simple and easy-to-make harvester. Piezoelectric materials that convert vibrations from human activities into energy were applied. A digital multi-meter was used to continually monitor the voltage output of the system. Three trials were done per monitoring. Actual testing to light emitting diode was also performed. Data showed that an output voltage was successfully generated. An average output voltage of 0.52V had a charging time of seconds, 1.03V in seconds, 1.52V in seconds, 2.02V in seconds, and 2.34V in seconds. An average discharging time of seconds per 1mV drop was also recorded. Results suggested that a fully charged device could have a theoretical continuous illumination of approximately 26 hours. In addition, the fabricated device successfully powered a light emitting diode for possible lighting purposes. The experiment established the viability of converting vibrations from human locomotion using a simple wooden box energy harvester and the potential of vibration as one of the most promising sources of energy for powering devices with low voltage electric requirements. Keywords: vibrations, energy, piezoelectric Correspondence to : Reisha Claffel Z. Ferraren (reishaferraren@yahoo.com)

2 1. INTRODUCTION APEC Youth Scientist Journal Vol.7 / No Background of the Study Energy harvesting has been subjected to discussion and research these last three decades. Due to the increasing demands of energy, the discovery and development of more energy resources has become an everyday task. Solar farms, geothermal energy farms, and wind farms are just some of the many conventional energy harvesting programs. These programs have only improved drastically due to the emergence of advanced technology (Dikshit et al., 2010). However, there are some significant concerns and disadvantages to these various energy harvesting programs. In solar power harvesting, a major concern presents itself in the solar cell, which is quite expensive but does not generate much power (Sampath et al., 2011). Due to the disadvantages of these energy harvesting programs, a new type of energy harvesting has manifested in today s technology: piezoelectricity. Piezoelectricity is the ability of certain solid, crystalline materials to produce an electric charge in response or proportional to mechanical stress. It was discovered by Jacques and Pierre Curie in 1880 (Jaffe, 2012). In relation, a phenomenon called the piezoelectric effect occurs when an electric charge is created as a force is administered to a piezoelectric material. For instance, piezoelectric materials are now implanted in highways to generate or produce electricity. In addition, piezoelectric materials also find itself useful in the recognition and identification of sonar waves (Mehta et al., 2013). Similarly, this study explains and expands the application of piezoelectric materials to generate or create electricity for public streetlights. Today, public street lighting technology has come a long way from lamps and incandescent bulbs. This past decade has seen the rising demand and popularity of the light emitting diode (LED) as the new lighting technology for street lighting due to its low-power consumption and high durability, to name a few of its desirable qualities (Carter et al., 2011). In this study, a simple prototype energy harvester from human activities using piezoelectricity was designed and tested in lighting an LED. This project is in growing response to the present energy crisis situation in the Philippines as reported by the Department of Energy (

3 APEC Youth Scientist Journal Vol.7 / No Objectives of the Study This study mainly aimed to fabricate and test a simple human locomotion energy harvester using piezoelectric technology in powering an LED. Specifically, it aimed to: 1. measure the output voltage of the device; 2. determine the charging and discharging time of the device; and 3. test its ability to illuminate a single round Light Emitting Diode (LED) Significance of the Study Due to the clear disadvantage of using fossil fuels as a source of energy and the looming disastrous possibilities if the world continues to use it as such, scientists and innovators alike are exploring new ways to harnessing energy without harming the environment. This study may provide better alternatives in harnessing energy without the high cost and with minimal maintenance using cheap piezoelectric materials. Moreover, the application of piezoelectric materials shows potential enough for companies to apply and construct different environment-friendly products Scope and Limitations This study tested the device with only one 3mm round LED attached to the circuit. Also, the specific amount of voltage used to acquire the average amount of time to store electricity was limited to 0.500V. Moreover, the voltage interval used to measure the estimated discharge time was only 0.001V. For example, the discharge time between 0.500V and 0.499V. 2. MATERIALS AND METHODS 2.1. Principle of Operation The conversion chain for the vibration energy harvesting principle starts with a mechanical energy source from human activities that could either be steps or taps. The vibrations are then transformed into electrical energy with an aid of piezoelectric element as

4 APEC Youth Scientist Journal Vol.7 / No.2 shown in Figure 2. The electrical output is thereafter formatted by a static converter before supplying to a storage system or to an electrical device, an LED-based flashlight for example. Figure 1: The typical schematic circuit diagram for a piezoelectric generator Copyright 2014 Matthew Zelisko, GK-12 Program, University of Houston 2.2. Construction of Simple Energy Harvester Two wooden boards with dimensions 51.1cm x 36cm x 2.4cm were prepared. One of these wooden boards served as the cover while the other was attached with thirty piezoelectric materials, each having a distance of 2.5cm from one another, in a 6 by 5 manner of arrangement. The said piezoelectric materials were connected as a series connection. These were then connected to a circuit consisting of two V μf capacitors, a toggle switch, a 3mm round light emitting diode (LED), and an AC-to-DC rectifier, which is composed of four 1N4148 type diodes. The overall circuit is shown in Figure 2. A small spring having a free length of 3.2cm was placed onto each piezoelectric material in order for the stress to be really applied on the plate inside the said material. The piezoelectric materials were placed in the middle of the two wooden boards as shown in Figure 3. The set-up was fixed in such a way that it can be reproduced easily. Figure 2: The overall circuit diagram of the fabricated energy harvester

5 APEC Youth Scientist Journal Vol.7 / No.2 terminal (-) cover terminal (+) base capacitors switch piezoelectric spring Front view Back view Figure 3: The fabricated human locomotion energy harvester 2.3. Testing of Fabricated Device For characterization as depicted in Figure 4, the fabricated device was connected to a digital multi-tester and human locomotion, in the form of steps, was done to create vibrations. The person stepped on the wooden board at the rate of approximately two steps per second. The voltage output as a function of charging time until the occurrence of a fully charge capacitor was recorded. In addition, the discharging time per 1mV was also monitored. Three trials were conducted for each parameter. Figure 4: Experimental set-up for voltage output measurement and the powering test for LED: (a) stepping on the wooden board, (b) and (c) pushing on the wooden board, (d) LED illumination after conduct of human locomotion

6 Charging Time (in seconds) 3. RESULTS AND DISCUSSION APEC Youth Scientist Journal Vol.7 / No.2 Table 1 shows the output voltage of the fabricated energy harvester as vibrations caused by human locomotion were set up on the device. Data showed that voltages were successfully generated with magnitude linearly dependent on the charging period as illustrated in Figure 5. According to Liao et al., 2004, as the capacitor starts to charge, the voltage across the capacitor increases. This is shown in Equation 1. (Equation 1) Table 1: Output voltage as a function of charging period Average Voltage Charging Time (in seconds) Output Trial 1 Trial 2 Trial 3 Mean ± SD 0.52V ± V ± V ± V ± V ± 0.62 Data further revealed that the maximum output voltage of the designed energy harvester was about 2.34V. This means that the designed energy harvester is capable of powering low voltage source devices and had successfully powered a light emitting diode for possible lighting purposes as shown in Figure 6. Data further showed that the average discharging time per 1mV drop of the stored energy was about seconds as shown in Figure 7. This implies that it would take about 26 hours (theoretical time) to fully discharge the capacitors and to fully die out the illumination produced by the LED y = x 0 R² = Voltage Output (in V) Figure 5: Voltage output model predictor using linear regression analysis

7 Discharging Time per mv (in seconds) APEC Youth Scientist Journal Vol.7 / No.2 Figure 6: VIBRA-E successfully powering the light emitting diode (LED): (a) vibrations initiated; no LED illumination, (b) start of LED illumination with constant vibrations, (c) vibrations stopped; LED illumination continues ±7.13 Voltage (in V) Figure 7: Discharging time for every 1mV Results suggested the viability of low vibrations generated by simple and easy to fabricate energy harvester as one of the most promising renewable and reliable solutions for powering low voltage electronic devices. Results also revealed the potential of the generated power to be an alternative to battery in the future because vibrations are found everywhere. 4. CONCLUSION AND RECOMMENDATIONS A simple vibrational energy harvester device was successfully fabricated and tested. The gathered data established the potential of converting vibrations into electrical energy and of powering low voltage gadgets such as light emitting diode. Harvesting vibrational energy from the environment through a simple device may be considered as a viable option to replace the current power supplies for energy constrained embedded systems. It is recommended that other data be gathered such as the individual charging time, discharging time, and voltage output of only one piezoelectric material, and the light intensity of the LED during illumination. Improvements could also be done on the device such as using acrylic glass instead of the wooden board as cover for better aesthetic appearance and durability

8 5. ACKNOWLEDGEMENTS APEC Youth Scientist Journal Vol.7 / No.2 The researchers would like to thank the following: Mr. Benito A. Baje, for suggesting the topic of this study and for being the researchers official adviser; Enthusiastic Inventors and Sci-Tech Innovators (EINSTEIN) Club of PSHS-CVisC, for all the help its members gave; Mr. Anthony A. Tabay, Mr. George Tagalog, and Kuya Islaw, for assisting during the making of the device; friends and families especially, Mrs. Anabel A. Muaña, Mr. Peter Ricardo R. Muaña, Mrs. Catherine Z. Ferraren, and Mr. Rogelio O. Ferraren Jr., for the help and support they have given for this study to be a successful one; Prof. Ashwani K. Gupta, for the wonderful AMGS journey; and of course, The Almighty Father, for everything. 6. REFERENCES [1] Carter, D., Quick, S., Danes, S., Gatti, E., & Brani, K. (2011). Pittsburgh LED Street Light Research Project. [2] Dikshit, T., Shrivastava, D., Gorey, A., Gupta, A., Parandkar, P., & Katiyal, S. (2010). Energy Harvesting via Piezoelectricity, 2(4), [3] Jaffe, B. (2012). Piezoelectric Ceramics (p. 1). Academic Press London and New York. [4] Liao, S., Dourmashkin, P., & Belcher, J. (2004). Direct-Current Circuits. In Physics 8.02 Electricity and Magnetism at MIT Modules. [5] Mehta, D., & Arun V, P. (2013). Eco-Friendly Electricity Generator Using Scintillating Piezo.Pratibha Arun V Et Al. Int. Journal of Engineering Research and Applications, 3(5), [6] Sampath, A., Thiyagarajan, S., A.M, A., & V, A. (2011). A Novel Approach to Recycle Energy Using Piezoelectric Crystals, 2(6), Reisha Claffel Z. Ferraren Peter Gabriel A. Muaña