Pyroelectric-Based Solar and Wind Energy Harvesting ... - IEEE Xplore

IEEE TRANSACTIONS ON SUSTAINABLE ENERGY, VOL. 5, NO. 1, JANUARY 2014

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Pyroelectric-Based Solar and Wind Energy Harvesting System S. Harihara Krishnan, D. Ezhilarasi, G. Uma, and M. Umapathy

Abstract—Inherent scarcity of thermal sources with a time varying temperature profile is the reason why the pyroelectric-based energy harvesting is not as prominent as its counterpart, thermoelectric generators, in the thermal energy harvesting domain. In this paper, a practical solution for generating thermal oscillations required for sustainable pyroelectric-based energy harvesting from the solar and wind energies, is presented. The main focus of the work is to modulate the concentrated solar radiation using a vertical axis wind turbine for producing higher rate of change of temperature on the pyroelectric material. The maximum energy and power density produced by the prototype device using PZT-5H as pyroelectric material are 6.927 mJ/cm /cycle and 421.18 W/cm , respectively, and on average it can produce a power density of 304.78 W/cm , which concurs with the theoretical model. Index Terms—Energy harvesting, pyroelectricity, solar energy, wind energy.

I. INTRODUCTION

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IVEN the inexorable quest by the electronics engineers to shrink the size of electronic circuits, the density and speed of the integrated circuits have seen exponential increase, in the pursuit of reaching the Moore’s law limits. This has opened gates to try and explore ways to develop devices that can convert ambient energy sources into useful electrical form, so that the electronic devices can become self-powered and maintenance-free. Among the many energy resources, solar and wind are the main contenders in terms of renewable, sustainable, and clean energy. Solar energy can be harvested in many ways, like by solar thermal power plants or by solar thermoelectric generators or by photovoltaic. The latter two possess advantages over the solar thermal power plants as they provide direct electrical output and they are suitable for small-scale installations [1], [2]. The solar thermoelectric generators make use of the Seebeck effect to generate voltage from a spatial thermal gradient. Instead, the temporal changes of thermal energy can be captured by means of pyroelectricity. The existence of spontaneous polarization, which is a permanent electric dipole moment with a specific crystal axis, is the basic constraint for a material to exhibit pyroelectricity. It is Manuscript received December 14, 2012; revised June 06, 2013; accepted July 12, 2013. Date of publication August 15, 2013; date of current version December 12, 2013. The authors are with the Department of Instrumentation and Control Engineering, National Institute of Technology, Tiruchirappalli 620015, India (e-mail: [email protected]; [email protected]; [email protected]; [email protected]). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TSTE.2013.2273980

the vulnerability of this spontaneous polarization to thermal changes which leads to charge redistribution on the surface of the material resulting in a current flow in an external circuit and thus creating a physical phenomenon called pyroelectricity [3]. There have been many studies related to pyroelectric-based energy harvesting mostly involving the Olsen cycle [4], which is based on the thermodynamic Ericsson cycle, with two isothermal and two isoelectric field processes. This cycle has been realized for different materials like polymers, single crystals, and relaxor ferroelectrics and for different electrical fields and temperature ranges. It should be noted that the presence of an electric field allows the thermodynamic cycle to operate around the Curie temperature where phase transition occurs between the ferroelectric and paraelectric and subsequent large changes in polarization. Navid et al. performed the Olsen cycle by alternatively dipping purified and porous 60/40 poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] in hot and cold silicone oil baths in the presence of electric fields and harvested maximum energy density up to 426 J/L/cycle [5]. Kandilian et al. performed the dipping experiment on 68PbMg Nb O -32PbTiO (PMN-32PT) single crystal and obtained energy density of 100 mJ/cm /cycle corresponding to the power density of 4.92 mW/cm [6]. Recently, Lee et al. harvested a maximum energy density of 888 J/L/cycle from oil bath experiments on 290- m-thick lanthanum-doped lead zirconate titanate (8/65/35 PLZT) ferroelectric relaxor crystal [7]. The other well-known method to perform an Olsen cycle is to force a working fluid, usually silicone oil, back and forth across a stack of pyroelectric material between heating and cooling heat exchangers. The systems were optimized for different viscosities and frequency of oscillation of the working fluid, operating temperatures, and electrical field ranges. Navid et al. achieved a power density of 38.4 W/L at 0.5-Hz frequency with lead zirconate stannate titanate (PZST) as the pyroelectric material [8]. Similar experiments were carried out by Nguyen et al. on 60/40 P(VDF-TrFE) and a maximum energy density of 130 J/L at 0.061-Hz frequency was obtained [9]. Alternatively, Lee et al. generated the thermal oscillations to carry out the Olsen cycle by alternatively placing 60/40 P(VDF-TrFE) on a hot and cold source instead of convective mode of heat transfer. The authors reported an energy density of 155 J/L/cycle at 0.066 Hz for temperatures between 25 C and 110 C [10]. However, there were attempts to extract energy from pyroelectric material in non-Olsen-cycle ways. Xie et al. used a resistance heater to create the temperature changes on a lead zirconate titanate (PZT-5A) ceramic and measured a peak power density of 0.23 W/cm , for a rate of change of temperature of

1949-3029 © 2013 IEEE

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Fig. 1. Principle of operation of the pyroelectric energy harvesting system.

15 Cs [11]. Mane et al. used a heat lamp as a radiation source and a rotating disc with an aperture as a radiation chopper to periodically heat three different materials such as PZT, a prestressed PZT composite, and single crystal PMN-30PT. Among the three, a maximum power density of 8.64 W/cm was generated by PMN-30PT for a temperature rate of 8.5 Cs because of its high pyroelectric coefficient [12]. The possibilities of directly taping ambient thermal sources through pyroelectricity, instead of pumping working fluid or using heat lamp, are seriously hampered by the lack of thermal sources with a large time varying temperature. Recently, Zhang et al. demonstrated that the pyroelectric material PZT when placed in solar radiation can produce energy by exploiting the natural fluctuations in solar radiation intensity and the fluctuations created by the wind [13]. The authors conducted a laboratory experimental procedure which modeled the actual situation and achieved a power density of 4.2 W/cm for a rate of change of temperature of 0.53 Cs for a wind speed of 2 ms . Similarly, Sebald et al. observed natural temperature variations on a coat and applied the temperature profile on a 0.75Pb(Mg Nb )O -0.25PbTiO (PMN-0.25PT) ceramic and estimated a mean power density of 1 W/cm from the material [14]. The harvested energy by these principles is very low because the natural fluctuations of solar radiation are too slow and very small to produce rapid changes in temperature. In this paper, a new solar energy harvesting system through pyroelectricity, which does not require any external means to generate thermal fluctuations other than wind energy, is proposed. It employs an optical concentration system to produce large thermal oscillations. The paper has the following structure. First the design of the system is explained followed by theory and experimental setup, and finally, the results and discussion.

II. DESIGN OF THE PROPOSED ENERGY HARVESTING SYSTEM A. Operating Principle The principle of the proposed energy harvesting system relies on the increased intensity of solar radiation on the pyroelectric material by means of an optical concentration system. By concentrating solar radiation, higher temperature can be achieved which may not be possible by normal exposure to solar radiation. And this incident concentrated radiation on the pyroelectric material has to be modulated in order that the pyroelectric material heating is periodic. Modulation can be achieved by means of a rotating mechanical chopper disc which is placed in between the optical concentration system and the pyroelectric material. The energy required to rotate the chopper can be derived from the kinetic energy of the wind by means of a wind turbine attached to the optical concentration system. The mechanical energy input from the wind turbine is transmitted to the chopper disc using a belt drive mechanism via a speed reduction unit. The speed reduction unit is necessary in order to reduce speed of rotation of the chopper disc, so that the active material will have a longer period of heating and cooling resulting in a high rate of change of temperature. Further, a heat sink is placed under the pyroelectric material with good thermal contact to passively cool the material during the cooling phase of the thermal cycle. The top surface of heat sink is coated with a thin electrical insulation layer in order to prevent power loss through the heat sink, as shown in Fig. 1. B. Selection of Components Optical concentrators can be either the reflective type, like those which use parabolic trough, or the refractive type, like

KRISHNAN et al.: PYROELECTRIC-BASED SOLAR AND WIND ENERGY HARVESTING SYSTEM

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the schematic diagram of the fully assembled pyroelectric energy harvesting system. III. MODELING ANALYSIS The power output from the pyroelectric material using the proposed design principle can be estimated analytically. Effects of both solar and wind energies on the time-dependent temperature profile of the pyroelectric material must be accounted, as it can be directly related to the generated pyroelectric current by the following equation [12]: (1)

Fig. 2. Schematic diagram of the proposed pyroelectric energy harvesting system showing major components.

those which employ Fresnel lens [15]–[17]. However, these concentrating devices require tracking systems in order to follow the sun precisely and they are able to concentrate only the beam or direct radiation from the sun. Though an imaging type Fresnel lens, which actually transfers the image of the sun onto the receiver, falls short of the maximum concentration limit due to the chromatic aberrations [18], [19], the concentration attained by the optical system is adequate to elevate the temperature of the pyroelectric material within its Curie temperature when placed in its focal zone. Thus, for the proposed energy harvesting system, an imaging type Fresnel lens is used for concentrating the solar radiation, but this optical concentration system requires a full tracking system [20]. The Fresnel lens also poses various advantages like it is light weight, more compact, low cost, and can be mass produced. The wind turbine, which provides the mechanical input to the chopper disc, has to be attached to the optical concentration unit which in turn will be aligned into the direction of the sun. So it would be reasonable to use a vertical axis wind turbine (VAWT) which can capture wind from any direction regardless of its orientation [21]. Among the two common types of vertical axis wind turbines, Savonius and Darrieus wind turbines, the former is selected because of its simple design and good starting torque when compared to Darrieus turbine which is not self-starting and often requires an induction motor or a Savonius rotor, as a starter [22]. But one should note that the Savonius turbine is less efficient in extracting power from the wind producing peak power coefficient when the tip speed ratio is less than one [23]. Hence, it is more suitable for low rotations per minute (rpm) applications, which is the present situation. Fig. 2 shows

is the surface area of the pyroelectric material and where is the pyroelectric coefficient of the material. Assuming uniform wind velocity (m/s), for the given speed reduction ratio and diameter (m) of the Savonius wind turbine and the mechanical efficiency of the whole wind turbine setup ; the time period (in seconds) of the pulsed radiation flux generated by chopping the concentrated solar radiation is (2) The “on” time period of the pulsed signal is equal to corresponding to the cut portion of the chopper disc and the incident pulsed radiation is given by (3) (W/m ) is the solar radiation intensity and where corresponds to the degree of concentration which is the ratio of area of the Fresnel lens to the surface area of the pyroelectric material. When such concentrated radiation pulses irradiates the pyroelectric material, a thermal heating cooling cycle sets in and a lumped capacitance model can be assumed in order to carry out the transient heat conduction analysis to find the temperature profile of the crystal. Such lumped model can be assumed only if the system has very small Biot number . The computed Biot number is 0.0017 hence, the assumption of uniform temperature distribution within the ceramic is reasonable. The equations that govern temperature changes in the pyroelectric ceramic can be obtained by applying conservation of energy principle over the two time periods. Ignoring the radiation losses in order to make the equations simpler and solvable, and assuming all the other parameters except temperature independent of time, the governing equations are shown in (4), at the bottom of the page [24], where , , , and are the density (kg/m ), volume (m ), specific heat capacity (J/kg C), and radiation absorption coefficient of the pyroelectric material. is

(4)

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the ambient temperature ( C) and the average convection coefficients and can be calculated by treating the condition as laminar air flow over a flat plate under constant surface heat flux and laminar air flow over an isothermal flat plate, respectively. is the thermal resistance of the electrical insulation layer which is given by (5) where , , and are the thickness (m), thermal conductivity (W/mK), and surface area (m ) of the electrical insulation layer. and are the thermal resistance of base and fins of the heat sink whose values can be calculated from the well established theory on the heat transfer from the extended surfaces [24]. Thus the linear nonhomogenous first-order differential equations (4) can be solved for , using the initial condition , as shown in (6) at the bottom of the page, where

and

And the generated current from the pyroelectric material can be found by using (1) and (6). For calculating the power density generated by the pyroelectric material for a load resistance connected across it, a lumped electrical model is assumed for the active element which is a current source in parallel with an internal capacitance and a leakage resistance [28], [29]. IV. EXPERIMENTAL SETUP AND MEASUREMENT SYSTEM The performance potential of the above described energy harvesting technique has been investigated by an experimental setup shown in Fig. 3. Lead zirconate titanate (PZT) (PZT-5H supplied by Sparkler Ceramics, Pune, India), whose dimensions and properties are given in Table I, is used as the pyroelectric material. As given in Table I, the Curie temperature of the PZT-5H is 195 C and hence, the crystal’s temperature can be raised safely up to 115 C without causing damage to the pyroelectric property of the crystal. A point focusing Fresnel lens made up of polymethylmethacrylate having dimension 27.5 cm 27.5 cm, is held firmly on the top side of a steel frame with the flat surface of the lens facing the sun. At the

Fig. 3. Experimental setup showing the fully assembled unit consisting of the Savonius wind turbine and the Fresnel lens concentration system along with PZT-5H.

bottom side of the steel frame, an aluminium heat sink is kept exactly on the focal axis of the Fresnel lens. Table II gives the characteristics of the concentrated solar radiation spot as the distance between the Fresnel lens and the aluminium heat sink is varied. And the heat sink is kept at cm from the lens so that the concentrated spot size of the lens is almost the size of the pyroelectric material. This ensures uniform surface heating of the pyroelectric material and prevents secondary pyroelectric effect which may rise due to spot heating [25]. A thin layer of standard epoxy adhesive (Araldite) which is applied on top of the aluminium heat sink serves as an electrical insulator and it is a good thermal conductor with thermal conductivity of 0.4 W/mK [26], and hence it does not hinder the cooling of the crystal during the cooling phase of the thermal cycle [10]. The PZT-5H is placed on the epoxy layer of the heat sink and standard insulation tapes are used to hold the crystal at outer edges ensuring good thermal contact with the heat sink. Also the top electrode of the ceramic is blackened for better absorption of radiation. Moreover, a J-type thermocouple is placed on the top surface of the crystal and the measured temperature is assumed to be the temperature of the entire crystal as the thickness of the crystal is very small compared to its length. A polyvinyl chloride (PVC) pipe of diameter 10.16 cm and length of 30 cm is cut vertically into exactly two halves and they are fixed on a 20 cm 20 cm 0.5 cm wooden plate, as shown in Fig. 4(a), in order to get the required “S” shape of the Savonius wind turbine with bucket gap width of 3 cm and diameter of 17 cm. A hollow rectangular aluminium frame with proper bearing setup to hold the Savonius wind turbine is attached to one of the side supports of the steel frame,

(6)


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TABLE I DIMENSIONS AND PROPERTIES OF THE PZT-5H PYROELECTRIC CRYSTAL

Fig. 4. Dimensions of (a) Savonius vertical axis turbine and (b) Aluminium chopper disc.

TABLE II CHARACTERISTICS OF CONCENTRATED SOLAR RADIATION SPOT

Fig. 5. Measurement circuit.

V. RESULTS AND DISCUSSION A. Evaluation Through Analytical Modeling

as shown in Fig. 3. The rotations of the Savonius wind turbine is transferred to a three-stage plastic gear speed reduction unit using belt drive mechanism attached to the bottom tip of the wind turbine shaft. Two symmetrical sectors of 45 angle are cut out from an aluminium disc of 0.05 cm thick and 5 cm diameter , as shown in Fig. 4(b). And this disc is attached to the shaft of the final stage of the speed reduction unit. This thin aluminium chopper disc is placed between the Fresnel lens and the ferroelectric ceramic so that when it rotates, it chops the concentrated irradiation from the Fresnel lens onto the active material. The orientation of the whole steel frame setup along with the wind turbine is manually adjusted in order to align the Fresnel lens towards the direction of the sun throughout the day. To quantify the power generated by the pyroelectric material, a measurement circuit is designed using OPA454 operational amplifier (Texas Instruments), as shown in Fig. 5. OPA454 is selected in order to linearly measure the high voltages generated by the pyroelectric crystal across the load resistance . The operational amplifier OPA454 is biased with 40 V and the values of the load resistance are varied for impedance matching. The output from the measurement circuit is recorded by using Agilent Data Acquisition unit (34970A) along with the temperature details from the J-type thermocouple.

Using the design parameters of the experimental prototype and the PZT-5H properties from Table I, the analytical equations are implemented using MATLAB. For the Savonius wind turbine, is assumed to be 0.85 and the speed reduction ratio and mechanical efficiency of the wind turbine unit as and 0.42, respectively. The values for Prandtl number (Pr), kinematic viscosity and thermal conductivity of air required for the estimation of and are obtained from standard table of thermophysical properties of air at 37 C [25]. The and of PZT-5H are assumed to be 40 nF and 50 G . Fig. 6 shows the average power density produced by PZT-5H for a load resistance of 40 M for different solar radiation intensities and wind velocity conditions. It can be deduced from the Fig. 6 that higher power density is obtained when the solar insolation is high and the wind velocity is relatively low. B. Evaluation Through Experimental Prototype The fully assembled prototype along with the measurement system is tested in actual operating conditions. During testing, the atmospheric wind speed varied between 2.5 to 5.3 m/s and the ambient temperature was around 37 C. Fig. 7 shows a typical graph of simultaneously recorded temperature variations of the pyroelectric material and the corresponding output voltage from the measurement circuit for a load resistance of 40 M . The temperature of PZT-5H reached a maximum of 115.4 C and the output voltage reached a maximum and minimum of 35.816 and 21.774 V, respectively. From the graphs,

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Fig. 6. Analytical modeling results showing average power density produced by PZT-5H for various solar radiation intensity and wind velocities and m/s. in the figure refers to the maximum temperature reached by the ceramic for the given solar radiation intensity at

Fig. 7. Experimental results (a) temperature profile of PZT-5H and (b) output recorded for a load resistance of 40 M . voltage

it is observed that as the temperature of the pyroelectric material rises from the ambient temperature, the voltage produced by

shown

the material increases in the positive direction and when the rotating chopper disc blocks the input concentrated radiation, the temperature drops and the responds by decreasing to reach negative maximum. It is to be noted that the fluctuations of the wind velocity affect the radiation chopping frequency and hence the durations of heating and cooling phases of the thermal cycle which eventually dictate the maximum and minimum temperature reached by the active material for a particular value of the solar radiation intensity. Fig. 8 provides the rate of change of temperature obtained when the pyroelectric material is periodically heated along with the temperature and the generated voltage curves. The intensity of the sun radiation available at that particular time and the distance between the concentrating optics and the pyroelectric material determines the rate at which temperature of the ceramic rises. It is understandable that very large temperature rates could have been obtained by keeping the distance equal to the focal length of the lens but the penalty would be the permanent damage to the pyroelectric property of the pyroelectric material, as discussed in Section IV. For the given , the maximum positive rate obtained is 20 Cs . And the rate at which the temperature of PZT-5H falls depends on the passive cooling provided by the aluminium heat sink and the heat loss due to forced convection of wind and a peak value of 13 Cs is obtained. The rate of cooling is rapid at the beginning and it slows down as the temperature of the ceramic reaches the ambient temperature which explains the low slope region of the output voltage. Further, the variations in the solar irradiance on the recorded day (August 18, 2012) is given in the Appendix I. From Figs. 7 and 8, it is explicable that high power density is produced under the circumstances where the irradiation in-


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Fig. 8. Graph showing temperature variations and rate of change of temperature of PZT-5H and the corresponding generated voltage

TABLE III COMPARISON BETWEEN THREE DIFFERENT POWER DENSITY CATEGORIES

tensity is high and there is low wind speed which makes the chopper disc to rotate at low rpm so that a high rate of change of temperature is obtained. Based on this, the above graphs can be divided into three sections, each producing high (I), moderate (II), and low (III) power density outputs. The moderate power density scenario occurs when the sun radiation is comparatively moderate but the wind speed is low enough to produce fair rate of change of temperature. The power density produced by the ceramic will be relatively low for the cases where the irradiation intensity is low and the radiation chopping frequency is high due to high wind speed. The comparison between the three categories is given in the Table III, where is the rpm of the chopper disc and and are the mean value of the maximum positive and negative rates, all calculated during the time period of each category. Additionally, a study to find the matching load resistance in order to have maximum power transmission is conducted by varying the load resistance from 10 to 40 M in steps of 10 M and the recorded peak power densities are 96.14, 190,

.

255, and 421 W/cm , respectively. But the study is limited; as the load resistance value is increased beyond 40 M , the output voltage from the measurement circuit gets saturated to the bias voltage, thus preventing the actual power measurement. Thus, the graph in Fig. 8 proves that a large rate of change of temperatures can be created by utilizing the ambient solar and wind energies which resulted in higher power and energy densities (peak power density of 421 W/cm and a mean power density of 304.78 W/cm and the largest energy density achieved is 6.927 mJ/cm /cycle and on average 4.675 mJ/cm /cycle) compared to the previous attempts on direct pyroelectric energy conversions [11]–[14]. Moreover, the results demonstrate a significant fact that, with the help of concentrating optics and a proper cooling mechanism, a temperature profile oscillating between large temperature gradient can be obtained, which is, in general, rather difficult to find in nature. VI. CONCLUSION In this paper, a pyroelectric-based energy harvesting system which converts the radiant energy from the Sun into useful power is designed and tested. The principle aim of the present work is to maximize the rate of change of temperature of the pyroelectric material, as it directly influences the power output from the pyroelectric material using the freely available solar and wind energies. A well-known technique to increase solar intensity by means of concentrating solar collector based on Fresnel lens and the mechanical input from the Savonius

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REFERENCES

Fig. A. Variations in GHI and DNI on the recorded day (August 18, 2012).

Fig. B. Variations in GHI and DNI during the recorded time (August 18, 2012 from 01:10 P.M. to 01:30 P.M. IST).

wind turbine are combined to produce the desired large rate of change of temperature on the pyroelectric material PZT-5H. The distance between the pyroelectric material and Fresnel lens are adjusted to keep the maximum temperature of the active material well within its Curie temperature during testing. The test results confirm the anticipated high performance combination of solar and wind energy and the largest energy and power densities produced by the PZT-5H are 6.927 mJ/cm /cycle and 421 W/cm , respectively, which is substantially greater than the previous studies on direct pyroelectric energy conversion. The experimental prototype results are also supported by an analytical model developed based on the principle of conservation of energy. It is also observed that the variations in the generated power density depend on the intensity of the solar radiation and the wind speed. APPENDIX The solar radiation data for the recorded day (August 18, 2012) is obtained from the Centre for Wind Energy Technology (C-WET), Government of India organization (Solar Radiation Resource Assessment (SRRA)—Tiruchirappalli station). Fig. A shows the variations in the Global Horizontal Irradiance (GHI) and the Direct Normal Irradiance (DNI) on the recorded day. In addition, Fig. B shows the variations in the GHI and DNI during the recorded time 1:10 P.M. to 1:30 P.M. IST.

[1] S. Jian and S. Mingheng, “Numerical simulation of electric-thermal performance of a solar concentrating photovoltaic/thermal system,” in Proc. Power and Energy Engineering Conf., Wuhan, China, 2009, pp. 1–4. [2] K. McEnaney, D. Kraemer, Z. Ren, and G. Chen, “Modeling of concentrating solar thermoelectric generators,” J. Appl. Phys., vol. 110, no. 07, pp. 074502.1–074502.6, Oct. 2011. [3] Y.-S. Lee, “Thermal detectors,” in Principles of Terahertz Science and Technology, 1st ed. New York, NY, USA: Springer, 2009, ch. 4, pp. 151–152. [4] R. B. Olsen, D. A. Bruno, and J. M. Briscoe, “Pyroelectric conversion cycles,” J. Appl. Phys., vol. 58, no. 12, pp. 4709–4716, Dec. 1985. [5] A. Navid and L. Pilon, “Pyroelectric energy harvesting using Olsen cycles in purified and porous poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] thin films,” Smart Mater. Structures, vol. 20, no. 025012, p. 9, Jan. 2011. [6] R. Kandilian, A. Navid, and L. Pilon, “The Pyroelectric energy harvesting capabilities of PMN-PT near the morphotropic phase boundary,” Smart Mater. Structures, vol. 20, no. 055020, p. 10, Mar. 2011. [7] F. Y. Lee, S. Goljahi, I. M. McKinley, C. S. Lynch, and L. Pilon, “Pyroelectric waste heat energy harvesting using relaxor ferroelectric 8/65/35 PLZT and the Olsen cycle,” Smart Mater. Structures, vol. 21, no. 025021, p. 12, Dec. 2011. [8] A. Navid, D. Vanderpool, A. Bah, and L. Pilon, “Towards optimization of a pyroelectric energy converter for harvesting waste heat,” Int. J. Heat Mass Transfer, vol. 53, pp. 4060–4070, Jun. 2010. [9] H. Nguyen, A. Navid, and L. Pilon, “Pyroelectric energy converter using co-polymer P(VDF-TrFE) and Olsen cycle for waste heat energy harvesting,” Appl. Thermal Eng., vol. 30, pp. 2127–2137, May 2010. [10] F. Y. Lee, A. Navid, and L. Pilon, “Pyroelectric waste heat energy harvesting using heat conduction,” Appl. Thermal Eng., vol. 37, pp. 30–37, Dec. 2011. [11] J. Xie, P. P. Mane, C. W. Green, K. M. Moss, and K. K. Leang, “Energy harvesting by pyroelectric effect using PZT,” in Proc. ASME Conf. Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS08), Maryland, USA, 2008, pp. 1–5. [12] P. Mane, J. Xie, K. K. Leang, and K. Mossi, “Cyclic energy harvesting from pyroelectric materials,” IEEE Trans. Ultrason., Ferroelectr., Freq. Control, vol. 58, no. 1, pp. 10–17, Jan. 2011. [13] Q. Zhang, A. Agbossou, Z. Feng, and M. Cosnier, “Solar micro-energy harvesting with pyroelectric effect and wind flow,” Sens. Actuators A, Phys., vol. 168, pp. 335–342, May 2011. [14] G. Sebald, D. Guyomar, and A. Agbossou, “On thermoelectric and pyroelectric energy harvesting,” Smart Mater. Structures, vol. 18, no. 125006, p. 7, Sep. 2009. [15] N. S. Kumar, K. Matty, E. Rita, W. Simon, A. Ortrun, C. Alex, W. Roland, G. Tim, and M. T. Kumar, “Experimental validation of a heat transfer model for concentrating photovoltaic system,” Appl. Thermal Eng., vol. 33–34, pp. 175–182, Oct. 2011. [16] S. A. Kalogirou, “Solar thermal collectors and applications,” Prog. Energy Combust. Sci., vol. 30, pp. 231–295, Feb. 2004. [17] Y. Wu, P. Eames, T. Mallick, and M. Sabry, “Experimental characterisation of a fresnel lens photovoltaic concentrating system,” Solar Energy, vol. 86, pp. 430–440, Dec. 2011. [18] G. Smestad, H. Ries, R. Winston, and E. Yablonovitch, “The thermodynamic limits of light concentrators,” Solar Energy Mater., vol. 21, pp. 99–111, 1990. [19] R. Winston, J. C. Minano, and P. G. Benitez, “Some basic ideas in geometrical optics,” in Nonimaging Optics, 1st ed. Burlington: Elsevier Academic, 2005, ch. 2, pp. 7–15. [20] G. N. Tiwari, “Solar concentrators,” in Solar Energy: Fundamentals, Design, Modeling and Applications, 1st ed. New Delhi, India: Narosa Pub. House, 2002, ch. 8, pp. 271–272. [21] A. Hemami, “Wind Turbine Basic Types: Analysis and Characteristics,” in Wind Turbine Technology, 1st ed. New York, NY, USA: Cengage Learning, 2012, ch. 4, pp. 47–61. [22] I. Paraschivoiu, “Savonius rotor,” in Wind Turbine Design: With Emphasis on Darrieus Concept, 1st ed. Montreal, Canada: Polytechnic Int. Press, 2002, ch. 2, pp. 20–22. [23] J. F. Manwell, J. G. McGowan, and A. L. Rogers, “Aerodynamics of wind turbines,” in Wind Energy Explained: Theory, Design and Application, 2nd ed. Hoboken, NJ, USA: Wiley, 2009, ch. 3, pp. 152–153.


[24] F. P. Incropera, D. P. DeWitt, T. L. Bergman, and A. S. Lavine, “Steady state One-Dimensional Conduction, Time-Dependent Conduction and External Forced Convection,” in Introduction to Heat Transfer, 5th ed. Hoboken, NJ, USA: Wiley, 2007, ch. 3, pp. 137–161, ch. 5, pp. 256–269 and ch. 7, pp. 384–392, Asia. [25] J. F. Nye, “Thermodynamics of equilibrium properties of crystals,” in Physical Properties of Crystals: Their Representation by Tensors and Matrices. London, U.K.: Oxford Univ. Press, 1985, ch. 10, pp. 188–190. [26] Huntsman Advanced Materials, Araldite® 2011, Two Component Epoxy Paste Adhesive, 2011 [Online]. Available: http://www.intertronics.co.uk/data/ara2011.pdf [27] H. H. S. Chang, R. W. Whatmore, and Z. Huang, “Pyroelectric effect enhancement in laminate composites under short circuit condition,” J. Appl. Phys., vol. 106, no. 11, pp. 114110.1–114110.10, Dec. 2009. [28] A. Cuadras, M. Gasulla, and V. Ferrari, “Thermal energy harvesting through pyroelectricity,” Sens. Actuators A, Phys., vol. 158, pp. 132–139, Jan. 2010. [29] J. Fraden, “Physical Principles of Sensing,” in Handbook of Modern Sensors: Physics, Designs, and Applications, 3rd ed. New York, NY, USA: Springer, 2004, ch. 3, pp. 76–82. S. Harihara Krishnan was born in Thanjavur, Tamil Nadu, India, in 1986. He received the Bachelor’s degree in mechatronics engineering from Kumaraguru College of Technology, Coimbatore, India, in 2007. He is currently working toward the M.S. degree (by research) in the Instrumentation and Control Engineering Department, National Institute of Technology, Tiruchirappalli, India. From 2007 to 2009, he worked as Programmer Analyst in Cognizant Technology Solutions, Chennai. His research interests include design and development of energy harvesting systems and MEMS.

D. Ezhilarasi was born in Arakkonam, Tamil Nadu, India, in 1979. She received the Bachelor’s degree in electrical and electronics engineering from Madras University, India, in 2000, the Master’s degree in process control and instrumentation and the Ph.D. degree in identification and control of smart structures, both from National Institute of Technology, Tiruchirappalli (NITT), India, in 2003 and 2009, respectively. From 2003 to 2005, she worked as a Research Associate in the Department of Electrical and Electronics Engineering, NITT, and worked as a Lecturer in the Department of Electrical and Electronics Engineering in the College of Engineering, Anna University, Chennai, in the year 2007–2008. She joined the Department of Instrumentation and Control Engineering as a faculty member, NITT, in 2009,

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where she is currently working as a Assistant Professor. Her research interests include energy harvesting using smart materials, system identification and control of smart structures, sliding mode control, and embedded systems.

G. Uma was born in Madurai, Tamil Nadu, India, in 1967. She received the Bachelor’s degree in instrumentation and control engineering from the Government College of Technology, Coimbatore, India, in 1989, the Master’s degree in instrumentation engineering from the Madras Institute of Technology, Anna University, Chennai, in 1992, and the Ph.D. degree in instrumentation and control from the National Institute of Technology, Tiruchirappalli, India, in 2009. She worked as a teaching research fellow in Madras Institute of Technology, Anna University, Chennai, from 1990 to 1993, and worked as a Senior Technical Officer in the Department of Science and Technology sponsored project “Development of cross correlation flow meter” in Madras Institute of Technology, Anna University, Chennai, from 1993 to 1994. She worked as a Head of the Department of Instrumentation and Control Engineering, Sethu Institute of Technology, Madurai, from 1995 to 1999. She joined the Department of Instrumentation and Control Engineering as a faculty member, National Institute of Technology, Tiruchirappalli, India, in 1999, where she is currently working as an Associate Professor. Her research interests include design and development of instrumentation systems, MEMS and process control. In 2001, Dr. Uma received a Young Scientist fellowship from Tamil Nadu State Council for Science and Technology under which she worked in the Thin Film Laboratory, Department of Instrumentation, Indian Institute of Science, Bangalore.

M. Umapathy was born in Ramanathapuram, Tamil Nadu, India, in 1967. He received the Bachelor’s degree in instrumentation and control engineering from the Government College of Technology, Coimbatore, India, in 1988, the Master’s degree in precision engineering and instrumentation from the Indian Institute of Technology Madras, Chennai, in 1990, and the Ph.D. degree in systems and control engineering from the Indian Institute of Technology Bombay, Mumbai, in 2001. He worked as a graduate engineer trainee in NLC Limited, Neyveli, India, for a year and served as scientist in DRDO, Government of India, Pune, India for six years. He joined the National Institute of Technology as a faculty member, Tiruchirappalli, India, in 1996, where he is currently working as a Professor in the Department of Instrumentation and Control Engineering. His research interests include smart structure modeling and control, smart materials, MEMS, and interval analysis.