Pyroelectric Harvesting Research Articles

Pyroelectric generators to harvest energy from disc brake pads for wireless sensors in electric vehicles

There is a large amount of thermal energy wasted during the driving cycle of all kinds of vehicles. In this paper, a pyroelectric harvester system, based on temperature change, is designed for low-powered sensors for the reliable electronic/electric architecture development of autonomous vehicles. In fact, this harvester was designed, specifically, in order to capture the temperature of the braking system and convert the wasted heat energy during the contact process to electrical energy. This conversion process occurs due to the temperature variation through the pyroelectric material, given the cooling phenomena of the ambient air. The energy potentially available in the form of heat produced by the friction involved in braking was evaluated using finite element analysis in the multiphysics software environment. Therefore, we present simulations of disc heating and cooling during the braking process at different speeds. Moreover, the potential for energy harvesting in multiple rolling conditions is discussed, such as the braking cycles and the effect of the material thickness used in the conversion module. The proposed system has undergone simulation analysis, which shows that the system can generate a voltage of 10.8 V and a power of 7.0 mW for a cycle of one braking process and around 9.5 mW for a cycle containing two successive braking's. The results of the simulation study verify the feasibility of the system and demonstrate its pertinence, especially for low-power sensors for new vehicle generations.

Sustainable solar energy harvesting using phase change material (PCM) embedded pyroelectric system

This work proposes a smart control of pyroelectric energy harvesting, based on the form-stable phase change material (PCM) composites utilizing polyethylene glycol (PEG) and 1-tetradecanol (1-TD). Solar light transmitted into a pyroelectric system made of window glass and indium tin oxide (ITO) pyro-electrode can provoke thermo-electric energy conversion by the change of temperature difference. The transparent pyro-electrode allows the transmitted solar light to reach the other side of the window glass. The PCM composite placed at the side can reduce the temperature fluctuation to control the change of temperature difference during the light-on/-off process. Since pyroelectric harvesting effects depends on the intensity of sunlight, different solar irradiations (10, 15, and 20 mW/cm2) were applied to the energy harvesting system in this study. The pyro-electrode could generate stable and continuous electrical energy by the combination of PCM composites. In addition, the underlying physics behind the system are theoretically modeled by utilizing the finite element method (FEM).

Energy generated through the pyroelectric effect using Macro-fiber Composites

Waste energy harvesting is a method of generating small amounts of energy, usually through vibrations or thermal energy. Macro-fiber Composites (MFCs) have been employed in energy harvesting applications utilizing the piezoelectric effect, however, energy harvesting using the pyroelectric effect in MFCs has not been thoroughly explored. This paper takes strides in investigating the energy generated using the pyroelectric effect with P1 and P2 MFCs using two different oscillating temperature rates at 5°C/min and 10°C/min. Numerical temperature data along with analytical temperature functions were used to model the pyroelectric effect and the result was compared to experimental tests. Depending on the size of the MFC, type, resistor used, and the temperature rate, the energy generated varies from 0.4 to 24 µJ for the P1 MFC, and 8 to 459 µJ for the P2 MFC. The maximum specific power was also estimated analytically, numerically, and experimentally. A resistor sweep was performed using the numerical model to calculate the optimal resistance that would provide the most energy. The resistor was in the Gigaohm (GΩ) to Teraohm (TΩ) range for the specified temperature profiles. The required resistance to generate the maximum energy decreased as the temperature rate and the size of the MFC increased. This was validated with experiments conducted at varying resistances. Because this is energy generated from the ambient environment, pyroelectric harvesting can be used to power devices without cost to the source. This form of harvesting can be used in any place where there is a natural thermal cycle (i.e. due to weather or machine giving off thermal energy).

Pyro-electrolytic water splitting for hydrogen generation

Water splitting by thermal cycling of a pyroelectric element that acts as an external charge source offers an alternative method to produce hydrogen from transient low-grade waste heat or natural temperature changes. In contrast to conventional energy harvesting, where the optimised load resistance is used to maximise the combination of current and voltage, for water splitting applications there is a need to optimise the system to achieve a sufficiently high potential difference for water electrolysis, whilst also maintaining a high current output. For the thermal harvesting system examined here, a high impedance 0.5 M KOH electrolyte with working electrodes connected to a rectified pyroelectric harvester produced the highest voltage of 2.34 V, which was sufficient for H2 generation. In addition to electrolyte concentration, the frequency of the temperature oscillations was examined and reducing the heating-cooling frequency led to a larger change in temperature to generate increased pyroelectric charge and a higher potential difference for pyro-water splitting. Finally, in the absence of sacrificial reagents, cyclic production of H2 (0.654 μmol/h) was demonstrated for the optimised processing parameters of electrolyte and thermal cycling frequency using the external pyroelectric element as a charge source for water splitting.

A strategy for optimal energy conversion by pyroelectricity

ABSTRACT The pyroelectric effect has been used for solar thermal energy harvesting to convert temporal temperature fluctuations into electrical energy to fully utilize abundantly available waste heat. A thicker pyroelectric cell is favorable when generating a higher induced voltage for a longer working period at a higher temperature. However, a thinner pyroelectric cell is favorable when generating a higher induced charge per period for a shorter working period at a lower temperature. Hence, integrating a thicker with a thinner pyroelectric cell is attempted to try to extend applications and increase the efficiency of pyroelectric harvesters when heat sources possess longer working periods and greater thermal fluctuations. The decline rate of the induced current for two PZT cells with the same thicknesses of 170 μm in a parallel circuit greatly increased when the working period was greater than 8 s. Two PZT cells with the same thicknesses of 420 μm in a parallel circuit could generate a larger induced charge per period than those of 170 μm in the parallel circuit when the working period was greater than 14 s. The working period was not taken into account when using the thicker PZT cells in the series or parallel circuits to harvest the induced charge. Moreover, two PZT cells with various thicknesses of 170 and 420 μm in a series possessed a moderate induced voltage and current benefiting stored voltage in a lower RL of 10MΩ.

Blowin' in the Wind – a Source of Energy: Hybrid Plasmonic and Pyroelectric Harvesting of Light Fluctuations (Advanced Optical Materials 11/2018)

In article number 1701051, Magnus P. Jonsson and co-workers present a concept for harvesting energy from light fluctuations. The concept utilizes metallic optical nanoantennas for the conversion of light fluctuations to thermal fluctuations. In turn, these thermal fluctuations are converted to electricity by an organic pyroelectric polymer. After systematic investigation of the concept, the authors demonstrate that their devices can harvest energy from light fluctuations induced by a leaf swinging in the wind.

Use it or lose it: The influence of second order effects of practical components on storing energy harvested by pyroelectric effects

Abstract Harvesting energy using the pyroelectric effect has seen growth as a potential energy source for low power applications, such as self-powered and autonomous wireless sensor networks. The scavenged energy is generally at low power levels, from mW to less than µW. While the voltages generated by pyroelectrics can be appreciable, the electric currents can be low in the order of nano-amps. In the case of pyroelectric harvesting the frequency of operation can also be low, typically much lower than 1 Hz, due to the slow temperature oscillations and transients in systems of large thermal mass. The combination of low power levels and low frequency of operation means that methods of storing electrical energy generated by pyroelectrics and the influence of inherent second order losses is of importance to create efficient harvesting devices. This paper examines the second order characteristic effects of practical capacitors and diodes for storage. The stored energy decay characteristics for commercially available components are examined and the data is used to characterise the second order effects. Selected components are then used in a pyroelectric harvesting system to determine potential improvements by appropriate selection of components with low loss.

Hybrid Plasmonic and Pyroelectric Harvesting of Light Fluctuations

AbstractState‐of‐the‐art solar energy harvesting systems based on photovoltaic technology require constant illumination for optimal operation. However, weather conditions and solar illumination tend to fluctuate. Here, a device is presented that extracts electrical energy from such light fluctuations. The concept combines light‐induced heating of gold nanodisks (acting as plasmonic optical nanoantennas), and an organic pyroelectric copolymer film (poly(vinylidenefluoride‐co‐trifluoroethylene)), that converts temperature changes into electrical signals. This hybrid device can repeatedly generate current pulses, not only upon the onset of illumination, but also when illumination is blocked. Detailed characterization highlights the key role of the polarization state of the copolymer, while the copolymer thickness has minor influence on performance. The results are fully consistent with plasmon‐assisted pyroelectric effects, as corroborated by combined optical and thermal simulations that match the experimental results. Owing to the tunability of plasmonic resonances, the presented concept is compatible with harvesting near infrared light while concurrently maintaining visible transparency.

Graphene Ink Laminate Structures on Poly(vinylidene difluoride) (PVDF) for Pyroelectric Thermal Energy Harvesting and Waste Heat Recovery.

Thermal energy can be effectively converted into electricity using pyroelectrics, which act as small scale power generator and energy harvesters providing nanowatts to milliwatts of electrical power. In this paper, a novel pyroelectric harvester based on free-standing poly(vinylidene difluoride) (PVDF) was manufactured that exploits the high thermal radiation absorbance of a screen printed graphene ink electrode structure to facilitate the conversion of the available thermal radiation energy into electrical energy. The use of interconnected graphene nanoplatelets (GNPs) as an electrode enable high thermal radiation absorbance and high electrical conductivity along with the ease of deposition using a screen print technique. For the asymmetric structure, the pyroelectric open-circuit voltage and closed-circuit current were measured, and the harvested electrical energy was stored in an external capacitor. For the graphene ink/PVDF/aluminum system the closed circuit pyroelectric current improves by 7.5 times, the open circuit voltage by 3.4 times, and the harvested energy by 25 times compared to a standard aluminum/PVDF/aluminum system electrode design, with a peak energy density of 1.13 μJ/cm3. For the pyroelectric device employed in this work, a complete manufacturing process and device characterization of these structures are reported along with the thermal conductivity of the graphene ink. The material combination presented here provides a new approach for delivering smart materials and structures, wireless technologies, and Internet of Things (IoT) devices.

Preparation and Characterization of BaTiO3–PbZrTiO3 Coating for Pyroelectric Energy Harvesting

Harvesting energy from waste heat is a promising field of research as there are significant energy recovery opportunities from various waste thermal energy sources. The present study reports pyroelectric energy harvesting using thick film prepared from a (x)BaTiO3–(1 − x)PbZr0.52Ti0.48O3 (BT–PZT) solid solution. The developed BT–PZT system is engineered to tune the ferro to paraelectric phase transition temperature of it in-between the phase transition temperature of BaTiO3 (393 K) and PbZrTiO3 (573 K) with higher pyroelectric figure-of-merit (FOM). The temperature-dependent dielectric behavior of the material has revealed the ferro- to paraelectric phase transition at 427 K with a maximum dielectric constant of 755. The room-temperature (298 K) pyroelectric coefficient (Pi) of the material was obtained as 738.63 μC/m2K which has yielded a significantly high FOM of 1745.8 J m−3 K−2. The enhancement in pyroelectric property is attributed to the morphotopic phase transition between tetragonal and rhombohedral PZT phases in the BT–PZT system. The developed BT–PZT system is capable of generating a power output of 1.3 mW/m2 near the Curie temperature with a constant rate (0.11 K/s) of heating. A signal conditioning circuit has been developed to rectify the time-varying current and voltage signals obtained from the harvester during heating cycles. The output voltage generated by the pyroelectric harvester has been stored in a capacitor for powering wearable electronics.

A Strip Cell in Pyroelectric Devices.

The pyroelectric effect affords the opportunity to convert temporal temperature fluctuations into usable electrical energy in order to develop abundantly available waste heat. A strip pyroelectric cell, used to enhance temperature variation rates by lateral temperature gradients and to reduce cell capacitance to further promote the induced voltage, is described as a means of improving pyroelectric energy transformation. A precision dicing saw was successfully applied in fabricating the pyroelectric cell with a strip form. The strip pyroelectric cell with a high-narrow cross section is able to greatly absorb thermal energy via the side walls of the strips, thereby inducing lateral temperature gradients and increasing temperature variation rates in a thicker pyroelectric cell. Both simulation and experimentation show that the strip pyroelectric cell improves the electrical outputs of pyroelectric cells and enhances the efficiency of pyroelectric harvesters. The strip-type pyroelectric cell has a larger temperature variation when compared to the trenched electrode and the original type, by about 1.9 and 2.4 times, respectively. The measured electrical output of the strip type demonstrates a conspicuous increase in stored energy as compared to the trenched electrode and the original type, by of about 15.6 and 19.8 times, respectively.

Photothermally Activated Pyroelectric Polymer Films for Harvesting of Solar Heat with a Hybrid Energy Cell Structure.

Photothermal effects in poly(3,4-ethylenedioxythiophene)s (PEDOTs) were explored for pyroelectric conversion. A poled ferroelectric film was coated on both sides with PEDOT via solution casting polymerization of EDOT, to give highly conductive and effective photothermal thin films of PEDOT. The PEDOT films not only provided heat source upon light exposure but worked as electrodes for the output energy from the pyroelectric layer in an energy harvester hybridized with a thermoelectric layer. Compared to a bare thermoelectric system under NIR irradiation, the photothermal-pyro-thermoelectric device showed more than 6 times higher thermoelectric output with the additional pyroelectric output. The photothermally driven pyroelectric harvesting film provided a very fast electric output with a high voltage output (Vout) of 15 V. The pyroelectric effect was significant due to the transparent and high photothermal PEDOT film, which could also work as an electrode. A hybrid energy harvester was assembled to enhance photoconversion efficiency (PCE) of a solar cell with a thermoelectric device operated by the photothermally generated heat. The PCE was increased more than 20% under sunlight irradiation (AM 1.5G) utilizing the transmitted light through the photovoltaic cell as a heat source that was converted into pyroelectric and thermoelectric output simultaneously from the high photothermal PEDOT electrodes. Overall, this work provides a dynamic and static hybrid energy cell to harvest solar energy in full spectral range and thermal energy, to allow solar powered switching of an electrochromic display.

Porous ferroelectrics for energy harvesting applications

This paper provides an overview of energy harvesting using ferroelectric materials, with a particular focus on the energy harvesting capabilities of porous ferroelectric ceramics for both piezo- and pyroelectric harvesting. The benefits of introducing porosity into ferro- electrics such as lead zirconate titanate (PZT) has been known for over 30 years, but the potential advantages for energy harvesting from both ambient vibrations and temperature fluctuations have not been studied in depth. The article briefly discusses piezoelectric and pyro- electric energy harvesting, before evaluating the potential benefits of porous materials for increasing energy harvesting figures of merits and electromechanical/electrothermal coupling factors. Established processing routes are evaluated in terms of the final porous structure and the resulting effects on the electrical, thermal and mechanical properties.

Porous PZT Ceramics with Aligned Pore Channels for Energy Harvesting Applications

In this study, aligned porous lead zirconate titanate (PZT) ceramics with high pyroelectric figures‐of‐merit were successfully manufactured by freeze casting using water‐based suspensions. The introduction of aligned pores was demonstrated to have a strong influence on the resultant porous ceramics, in terms of mechanical, dielectric, and pyroelectric properties. As the level of porosity was increased, the relative permittivity decreased, whereas the Curie temperature and dielectric loss increased. The aligned porous structure exhibited improvement in the compressive strength ranging from 19 to 35 MPa, leading to easier handling, better processability and wider applications for such type of porous material. Both types of pyroelectric harvesting figures‐of‐merit (FE and F′E) of the PZT ceramics with a porosity level of 25–45 vol% increased in all porous ceramics, for example, from 11.41 to 12.43 pJ/m3/K2 and 1.94 to 6.57 pm3/J, respectively, at 25°C, which were shown to be higher than the dense PZT counterpart.

Study on Pyroelectric Harvesters with Various Geometry.

Pyroelectric harvesters convert time-dependent temperature variations into electric current. The appropriate geometry of the pyroelectric cells, coupled with the optimal period of temperature fluctuations, is key to driving the optimal load resistance, which enhances the performance of pyroelectric harvesters. The induced charge increases when the thickness of the pyroelectric cells decreases. Moreover, the induced charge is extremely reduced for the thinner pyroelectric cell when not used for the optimal period. The maximum harvested power is achieved when a 100 μm-thick PZT (Lead zirconate titanate) cell is used to drive the optimal load resistance of about 40 MΩ. Moreover, the harvested power is greatly reduced when the working resistance diverges even slightly from the optimal load resistance. The stored voltage generated from the 75 μm-thick PZT cell is less than that from the 400 μm-thick PZT cell for a period longer than 64 s. Although the thinner PZT cell is advantageous in that it enhances the efficiency of the pyroelectric harvester, the much thinner 75 μm-thick PZT cell and the divergence from the optimal period further diminish the performance of the pyroelectric cell. Therefore, the designers of pyroelectric harvesters need to consider the coupling effect between the geometry of the pyroelectric cells and the optimal period of temperature fluctuations to drive the optimal load resistance.

Study on Pyroelectric Harvesters Integrating Solar Radiation with Wind Power

Pyroelectric harvesters use temperature fluctuations to generate electrical outputs. Solar radiation and waste heat are rich energy sources that can be harvested. Pyroelectric energy converters offer a novel and direct energy-conversion technology by transforming time-dependent temperatures directly into electricity. Moreover, the great challenge for pyroelectric energy harvesting lies in finding promising temperature variations or an alternating thermal loading in real situations. Hence, in this article, a novel pyroelectric harvester integrating solar radiation with wind power by the pyroelectric effect is proposed. Solar radiation is a thermal source, and wind is a dynamic potential. A disk generator is used for harvesting wind power. A mechanism is considered to convert the rotary energy of the disk generator to drive a shutter for generating temperature variations in pyroelectric cells using a planetary gear system. The optimal period of the pyroelectric cells is 35 s to harvest the stored energy, about 70 μJ, while the rotary velocity of the disk generator is about 31 RPM and the wind speed is about 1 m/s. In this state, the stored energy acquired from the pyroelectric harvester is about 75% more than that from the disk generator. Although the generated energy of the proposed pyroelectric harvester is less than that of the disk generator, the pyroelectric harvester plays a complementary role when the disk generator is inactive in situations of low wind speed.

Pyroelectric Harvesters for Generating Cyclic Energy

Pyroelectric energy conversion is a novel energy process which directly transforms waste heat energy from cyclic heating into electricity via the pyroelectric effect. Application of a periodic temperature profile to pyroelectric cells is necessary to achieve temperature variation rates for generating an electrical output. The critical consideration in the periodic temperature profile is the frequency or work cycle which is related to the properties and dimensions of the air layer; radiation power and material properties, as well as the dimensions and structure of the pyroelectric cells. This article aims to optimize pyroelectric harvesters by matching all these requirements. The optimal induced charge per period increases about 157% and the efficient period band decreases about 77%, when the thickness of the PZT cell decreases from 200 μm to 50 μm, about a 75% reduction. Moreover, when using the thinner PZT cell for harvesting the pyroelectric energy it is not easy to focus on a narrow band with the efficient period. However, the optimal output voltage and stored energy per period decrease about 50% and 74%, respectively, because the electrical capacitance of the 50 μm thick pyroelectric cell is about four times greater than that of the 200 μm thick pyroelectric cell. In addition, an experiment is used to verify that the work cycle to be able to critically affect the efficiency of PZT pyroelectric harvesters. Periods in the range between 3.6 s and 12.2 s are useful for harvesting thermal cyclic energy by pyroelectricity. The optimal frequency or work cycle can be applied in the design of a rotating shutter in order to control the heated and unheated periods of the pyroelectric cells to further enhance the amount of stored energy.

Finite element analysis on solar energy harvesting using ferroelectric polymer

Solar energy harvesting through pyroelectric effect has been under the scrutiny of researchers since the past few years. However, the low energy density coupled with requirement of rapid temperature fluctuations has hindered any successful commercial ventures in this field. This study is an attempt towards eliminating these drawbacks associated with pyroelectric energy generation using ferroelectric polymers. Langmuir–Blodgett Polyvinylidene difluoride copolymer–Trifluoroethylene–Chlorofluoroethylene P(VDF–TrFE–CFE) thin films were used in conjunction with pyroelectric effect and forced cooling to simultaneously increase energy and power density. In this regard, a two faceted approach of linear pyroelectric harvesting and harvesting through Ericsson cycle have been analyzed and compared. The models for the same have been developed and analyzed using finite-element method. Two separate cases of air cooling and water cooling were investigated. Peak values of power density for water cooling and air cooling processes (direct pyroelectric effect) are found to be 0.437μW/cm3 and 0.2μW/cm3, respectively. These values are obtained at optimized value of load resistance and load capacitance (RL=7MΩ and CL=2μF for water cooling while RL=14MΩ and CL=2μF for air cooling). The maximum values of power density that can be obtained from water and air cooling process are 19.65mW/cm3 and 16.35mW/cm3 (using Ericsson cycle) at 0.013 and 0.011Hz frequency, respectively. It was also observed that water cooling is more efficient than air cooling for energy harvesting. This study can lead to growth in the field of solar energy harvesting using pyroelectric effect.

A modified figure of merit for pyroelectric energy harvesting

This paper reports a new figure of merit for the selection of pyroelectric materials for thermal energy harvesting applications, for example, when the material is exposed to heat or radiation of a specified power density. The figure of merit put forward and developed is of interest to those selecting materials for the design of thermal harvesting devices or the development of novel ceramic, single-crystal and composite materials for pyroelectric harvesting applications.

Piezoelectric and ferroelectric materials and structures for energy harvesting applications

This review provides a detailed overview of the energy harvesting technologies associated with piezoelectric materials along with the closely related sub-classes of pyroelectrics and ferroelectrics. These properties are, in many cases, present in the same material, providing the intriguing prospect of a material that can harvest energy from multiple sources including vibration, thermal fluctuations and light. Piezoelectric materials are initially discussed in the context of harvesting mechanical energy from vibrations using inertial energy harvesting, which relies on the resistance of a mass to acceleration, and kinematic energy harvesting which directly couples the energy harvester to the relative movement of different parts of a source. Issues related to mode of operation, loss mechanisms and using non-linearity to enhance the operating frequency range are described along with the potential materials that could be employed for harvesting vibrations at elevated temperatures. In addition to inorganic piezoelectric materials, compliant piezoelectric materials are also discussed. Piezoelectric energy harvesting devices are complex multi-physics systems requiring advanced methodologies to maximise their performance. The research effort to develop optimisation methods for complex piezoelectric energy harvesters is then reviewed. The use of ferroelectric or multi-ferroic materials to convert light into chemical or electrical energy is then described in applications where the internal electric field can prevent electron–hole recombination or enhance chemical reactions at the ferroelectric surface. Finally, pyroelectric harvesting generates power from temperature fluctuations and this review covers the modes of pyroelectric harvesting such as simple resistive loading and Olsen cycles. Nano-scale pyroelectric systems and novel micro-electro-mechanical-systems designed to increase the operating frequency are discussed.