1. ENERGY HARVESTING UNDER EXCITATION OF UNIMORPH BEAM FOR SENSOR APPLICATIONS
Almuatasim Alomari, Ashok K. Batra, and Mohan Aggarwal
Materials Science Group, Department of Physics, Chemistry & Mathematics, Alabama A&M University, Normal, AL
DESIGN & TESTING OF A PIEZOELECTRIC ENERGY HARVESTER
DESIGN & TESTING PIEZOELECTRIC ENERGY HARVESTER USING COMSOL
ABSTRACT
Piezoelectric cantilever beams with polyvinylidene fluoride (PVDF) have been widely used as unimorph and bimorph to harvest vibration energy from ambient environment. The harvesting of ambient vibration energy for use in low energy electronic devices, such as, wireless sensor networks (WSN’s) has attracted significant interest. PVDF and its copolymers have high flexible energy harvesting devices and robust mechanical stability compared to inorganic materials. In this research, we report enhanced performances of poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) thick film based energy generators experimentally and theoretically. Experimental method was carried out using cheap cost effective solution-casting technique. The theoretical model was simulated and modeled based on Lumped parameter method (LPM) and finite element method (FEM), respectively.
CONCEPT: PIEZO–MICRO-ELECTRIC GENERATOR
A 2 dimensional (2D) of unimorph cantilever beam (UCB) with Iron beam are used for the simulation in COMSOL. The model is designed in COMSOL as shown below. The model consists of UCB with different lengths attached at the front of aluminum beam. The lengths of shim layer and piezomaterial are made equal. Using solid mechanics module, one end of the model is fixed and the other end is made to move freely with tip mass. Meshing a geometry is done using size parameters for free tetrahedral, with a fine mesh near the clamped end. The first mode shape of unimorph cantilever beam is shown at resonance frequency of 35 Hz as shown in figure below.
Capacitor
Resistance
LED
Switch
Diode
P(VDF-TrFE)
First Mode shape of Unimorph Cantilever Beam with Tip Mass
Meshed Unimorph Cantilever Beam with Tip Mass
PREPERATION PRINCIPLE OF A PIEZO-ELECTRIC FILM
P(VDF) powder
Methyl-Ethyl-Ketone (MEK) +
60oC for 24 hours
P(VDF-TrFE)
solvent
Solvent
Annealing
110oC for 2-3 hours
Silver coating
(Electrolyte) V
Film poling
60oC with 10kV/cm
for 2-3 hours
SMART MATERIALS PARAMETERS & CONSTITUENTS INVESTIGATED
Material Properties of Unimorph Cantilever beam
Unimorph cantilever beam
P(VDF-TrFE) layer
Cantilever beam
Length (mm) 20 55
Width (mm) 16
Thickness (mm)
0.15
0.2
Young’s Modulus (Gpa) 5
117
Density (kg/m3)
1800
7800
Dielectric constant 12
Piezo strain constant ( C/m)
-23
Capacitance (nF)
2.7
Electromechanical coefficient Ɵ (N/V)
4.5×10-5
Output Voltage and Electric Output Power Versus Frequency
Mechanical Input Power Versus Frequency
OBJECTIVES
Fabrication of P(VDF-TrFE)thick films under optimum conditions.
Characterization of the Films for electrical and piezoelectric properties.
Investigate experimentally and theoretically the output electrical parameters of piezoelectric samples fabricated in our laboratory and determine the efficiency of energy harvester.
Modeling the piezoelectric energy harvester devices using COMSOL Multiphysics and determine the output electrical performance parameters
ENERGY HARVESTING SIMULATION OF PIEZOELECTRIC
Output Voltage Versus Load Resistance
Mechanical Input Power and Electric Output Power Versus Load Resistance PC
Picoscope
Exitation Source Vibration Shaker
Amplifier
Brüel & Kjaer 2718
Controller Function Generator GF8046 ELENCO
Accelerometer
Brüel & Kjaer 4810
Measured Acceleration Experienced by EH
Voltage Output from EH
Channel 1
Channel 2
Sinusoidal Signal to Shaker
Laser
Microtrack II
mti Instruments
P(VDF-TrFE)
Film
THEOREITICAL & CIRCUIT TECHNIQUE OF PIZOELECTRIC
ENERGY HARVESTER (PEH)
Piezoelectric Element RL c k m
P(VDF-TrFE)
Film
Tip Mass x y z
Output Voltage and Electric Output Power Versus Acceleration
Mechanical input Power Versus Acceleration
Piezoelectric Cantilever Beam for Energy Harvesting
Lumped Parameter Model
RESULTS OF PIEZOELECTRIC ENERGY HARVESTER CANTILEVERS WITH CONFIGURATIONS
PIEZOELECTRIC ENERGY HARVESTING FORMULI
Experimental, Simulation, and Modeling Functional Parameters of Piezoelectric Energy Harvester
Acceleration Functional Response versus Output Voltage, Output Electrical Power, and Applied Mechanical Power of Piezoelectric Energy Harvester Using COMSOL Multiphysics
UCB
Experimental
Simulation
Error (%)
COMSOL
Resonance Frequency (Hz) 35
35.1
0.28
35.05
0.14
Output Voltage (mV)
50.5
60.9
20.5
62.1
22.7
Electric Power (nW)
12.7
18.5
45.6
9.5
25.7
Acceleration (g)
Output voltage (mV)
Electric Power (nW)
Mechanical Power (mW)
0.1 31
0.2
0.01 62
1.1
0.04
0.3 93
2.2
0.09
0.4
124
3.8
0.16
0.5
155 6
0.26
0.6
186
8.7
0.37
0.7
217
11.7
0.52
0.8
248
15.4
0.66
0.9
279
19.4
0.83 1
310 24
1.01
EXPERIMENTAL & THEORETICAL RESULTS USING MATLAB
Design by Sheral Carter, AAMU Physics Department 2016
INVESTIGATIONS OUTCOME
The preliminary results obtained can be summarized as follows:
Piezoelectric poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) is a valuable material, which can be used for energy conversion in different environment and applications.
Fabricated thick films with piezoelectric materials based on modified poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) type material system with high piezoelectric coefficients.
Characterized the fabricated modified piezoelectric elements for the dielectric and piezoelectric properties.
Simulation and modelling piezoelectric energy harvester with MATLAB program and COMSOL Multiphysics software showed good agreement between experimental and theoretical results.
Output Voltage Versus Frequency
Output Power Versus Frequency
REFERENCES
Cho, Y., Park, J. B., Kim, B. S., Lee, J., Hong, W. K., Park, I. K., ... & Kim, J. M. (2015). Enhanced energy harvesting based on surface morphology engineering of P (VDF-TrFE) film. Nano Energy, 16,
Tseng, H. J., Tian, W. C., & Wu, W. J. (2013). P (VDF-TrFE) polymer-based thin films deposited on stainless steel substrates treated using water dissociation for flexible tactile sensor development. Sensors, 13(11),
Tang, L., & Yang, Y. (2012). A multiple-degree-of-freedom piezoelectric energy harvesting model. Journal of Intelligent Material Systems and Structures, 23(14),
Emam, M. (2008). Finite element analysis of composite piezoelectric beam using comsol.
Erturk, A., & Inman, D. J. (2011). Piezoelectric energy harvesting. John Wiley & Sons.
c: Damping Coefficient
k: Spring Constant
ξT: Total Damping Ratio
Ep: Young’s Modulus of Piezoelectric Material
Es: Young’s Modulus of Substrate Material
lm: Length of Tip Mass, l: Length of the Beam, w: Width of the Beam
tp: Thickness of Piezoelectric Material, ts: Thickness of Substrate Material
mp: Tip Mass, me: Effective Mass, m: Beam Mass
ρp: Density of Piezoelectric Material, ρs: Density of Substrate Material
ACKNOWLEDGMENTS
The authors gratefully acknowledge support for this work through NSF grant # EPSCoR R-II-3 (EPS ). The authors thank Mr. Garland Sharp for fabrication of the sample holders.
Output Power Versus Load Resistance
Output Voltage Versus Load Resistance