Pyroelectric Generator Research Articles

Pyroelectric crystals for generation of neutrons: A review

Over 2300 years ago, the discovery of tourmaline led to the understanding of pyroelectric properties, which opened new doors to various applications of pyroelectric crystal, such as neutron and x-ray generation, energy harvesting, mass spectrometry, high-voltage sources, and more. In the last two decades, researchers have carried out extensive research and development to select components and materials and innovate the design and construction of the pyroelectric neutron generator (PNG). This manuscript investigates the process and history of the PNG’s development. It explains the physics governing pyroelectric crystals and the method of producing neutrons in a comprehensive and straightforward manner. Although PNGs have a lower yield and shorter lifetime compared to other neutron generators, they are still significant for research purposes due to their lack of need for an external high-voltage power supply, lower cost, smaller size, and safety. The main objective of this manuscript is to bring more attention to the research and development of PNGs. In recent years, new methods have been introduced that reduce the amount of neutron flux required for various applications. This has raised hope for the progress of commercial and industrial use of PNGs in the near future. The manuscript mentions some research cases that represent the future perspective of PNG development. Furthermore, the challenges faced by PNGs can be handled more efficiently with the utilization of generative learning algorithms and improvements in the components/mechanisms used for PNG design.

High-powered superhydrophobic pyroelectric generator via droplet impact

Recent studies on water-based pyroelectric generators (PEGs), which convert thermal energy to electrical energy, have focused on different operational modes like water evaporation, water stream, and droplet sliding. However, the development of sustainable, high-powered generators and comprehensive theoretical models has been limited. In response, our research introduces a droplet-based superhydrophobic pyroelectric generator (S-DPEG), exploiting the characteristics of lead magnesium niobate-lead titanate (PMN-0.3PT) coated with titanium dioxide nanoparticles. We analyzed power density by considering the phase transient temperature that maximizes the pyroelectric coefficient of PMN-0.3PT, testing various Weber numbers and droplet diameters within a moderate operating temperature range of 40°C to 80°C. Considering the dynamic characteristics of water droplet on superhydrophobic surfaces, we suggest a peak current model that can accurately predict the peak current within ∼15% of error. Also, the maximum power density of 54.5 μW/cm2 at a droplet diameter of 3.6 mm and a temperature of 80°C, a noteworthy improvement over 3 times higher than previous water-based PEGs. Our results enhance the understanding of the pyroelectric effect coupled with drop impact dynamics and outline novel strategies for designing high-performance water-based PEGs.

A novel hybrid pyroelectric-Stirling engine power generation system

Temperature fluctuations in the thermal regenerator of Stirling Engine SE occur at relatively high frequencies, making them amenable to direct harvesting using Pyroelectric materials. This paper demonstrates the technical feasibility of a novel hybrid Stirling Engine (SE), coupled with inserted pyroelectric generators in its thermal regenerator, to produce extra power through the pyroelectric effect and increase engine performance. Theoretical models have been constructed to analyze the performance of the pyroelectric-Stirling engine (P-SE) system and determine its advantages over conventional SEs. The transient thermal behavior of the pyroelectric regenerator is modeled by subdividing it into multiple lumped sub-regenerators. Replacing the metal regenerator in a conventional SE at 750 K hot chamber temperature with a pyroelectric regenerator increased power production by 2.9%. Furthermore, at 25 Hz fluctuation, 15 mm regenerator length, and regenerator porosity of 0.6, the system efficiency of the hybrid P-SE system increased by 0.5% and 3.5% compared to systems using steel and aluminum regenerators, respectively. Also, the P-SE system operating at 25 Hz yields the highest combined efficiency of 49.8% at the regenerator porosity of 0.6.

High-performance thermomagnetic generator controlled by a magnetocaloric switch

Low grade waste heat accounts for ~65% of total waste heat, but conventional waste heat recovery technology exhibits low conversion efficiency for low grade waste heat recovery. Hence, we designed a thermomagnetic generator for such applications. Unlike its usual role as the coil core or big magnetic yoke in previous works, here the magnetocaloric material acts as a switch that controls the magnetic circuit. This makes it not only have the advantage of flux reversal of the pretzel-like topology, but also present a simpler design, lower magnetic stray field, and higher performance by using less magnetocaloric material than preceding devices. The effects of key structural and system parameters were studied through a combination of experiments and finite element simulations. The optimized max power density PDmax produced by our device is significantly higher than those of other existing active thermomagnetic, thermo, and pyroelectric generators. Such high performance shows the effectiveness of our topology design of magnetic circuit with magnetocaloric switch.

Enhancement of a pyroelectric body energy harvesting scheme employing pulsed electric fields.

This research utilizes waste heat energy as a sustainable energy source to enhance pyroelectric power output by combining pyroelectric nanogenerators with an external pulsed electric field. When the surface temperature of the pyroelectric body varies, applying different pulses of the external electric field results in maximum power accumulation. A novel power-generating experimental setup was developed to measure and compute pyroelectric power generation. A standard Fuji ceramic C-9 sample was used to generate pyroelectric energy in a 20 °C temperature range from 120 to 140 °C. The continuous temperature variation frequency was 0.05Hz, and the pulsed electric field was applied when the temperature rose. Pulses of the electric field with widths of 10, 50, 100, and 200ms were applied to the sample under different pulse amplitudes, and the amplitude of each pulse was 250, 500, 1000, or 1500 V/mm. The maximum power generated through the application of an external pulsed electric field under the above-mentioned conditions was evaluated. This system had the highest power density of 0.204 mJ cm-2 °C-1kV-1. In addition, for the lowest input power, the maximum power generation condition was a 10ms pulse width and an amplitude of 250Vmm-1 in the applied electric field. This state might power smart sensor modules, IoT devices, automobiles, and other waste heat energy applications. Nano-pulse electric field applications may reduce input power to its lowest level, dependent on net-producing power. Therefore, new researchers can use net-generation power efficiency to create a large-scale power source using multiple pyroelectric arrays.

Improvement of Power Recovery by Applying a Multi-Pulse Electric Field in the Thermoelectric Cycle Power Generation Process with Pyroelectric Materials

Nanogenerator energy harvesting technologies that transform thermal energies into electricity may help address the growing need for green power. Therefore, this research aims to increase power generation by combining waste heat with pyroelectric nanogenerators as a sustainable energy source. Under optimal conditions, an external multi-pulse electric field can be utilized to generate power using thermoelectric cycle power generation. The greatest power may be gathered by applying various pulses of the external electric field at temperature changes on the surface of the pyroelectric materials. To generate pyroelectric power, a C9 BZT sample was used, and the lowest temperature difference for accomplishing this was 20 °C, with all measurements made on a sample with a lower limit of 120 °C. The maximum generation density was 0.104 mJ/cm2°CkV for a pulse width of 10 ms and 20 pulses of a low voltage (250 V/mm) input electric field. A multi-pulse electric field with low input voltage increases the power generation performance ratio (η) with the pulse count. At the largest number of pulses, the greatest η value for 250 V/mm was 7.834. Finally, it was determined that the developed pyroelectric power generation system may be more effective if a low-voltage, multi-pulse electric field is used.

Low-grade waste heat recovery scenarios: Pyroelectric, thermomagnetic, and thermogalvanic thermal energy harvesting

Identifying reliable and sustainable sources of electricity is a significant challenge of the present time. However, most energy-generation mechanisms produce unavoidable low-grade waste heat as a byproduct while harvesting (or converting) electrical energy from conventional or renewable energy sources. Each year, over 60% of the primary energy is wasted as heat. Accordingly, considerable efforts are being made to convert this waste heat into usable electrical energy using diverse energy conversion materials. In this review, three actively investigated energy conversion mechanisms beyond thermoelectrics, i.e., (1) pyroelectric, (2) thermomagnetic, and (3) thermogalvanic generators, are reviewed and compared from the viewpoint of fundamental theories, critical parameters for high energy conversion efficiency, and current status of materials and devices. The challenges and opportunities in low-grade waste-heat recovery are discussed in terms of material science and structural design. This review provides an overview of the current progress in thermal-energy-harvesting research, future challenges, and opportunities.

Continuous pyroelectric energy generation with cyclic magnetic phase transition for low-grade thermal energy harvesting

Waste heat harvesting is of importance to mitigate global warming so that thermoelectric devices have often been suggested; however, such approaches are challenging because of low conversion efficiency of thermoelectrics at low temperature gradient and easy thermal equilibration. In this study, a novel thermo-magneto-pyroelectric energy generator (TMPyEG) was developed to continuously harvest waste heat and convert it into electric energy without complicated electric bias field, required in typical thermodynamic cycling-based pyroelectric generators. To enable displacement reciprocation without intervention, the second-order magnetic phase transition of the soft magnet on an actuating part was repeated in the presence of a thermal gradient. We further incorporate piezoelectric material to mitigate crest factor by filling the energy gaps between pyroelectric energy outputs. Notably, the generated energy from pyroelectric conversion in TMPyEG is superior to that from the reported thermoelectric generators under the similar thermal conditions.

Demonstration of pyroelectric generation for self-powered wireless sensor nodes

Demonstration of pyroelectric generation for self-powered wireless sensor nodes

Anomaly in Pyroelectric Current Generation with Varying Lithium Tantalate Single Crystal Temperature with a Constant Rate

Anomaly in Pyroelectric Current Generation with Varying Lithium Tantalate Single Crystal Temperature with a Constant Rate

Achieving milliwatt level solar-to-pyroelectric energy harvesting via simultaneous boost to photothermal conversion and thermal diffusivity

Pyroelectric technology is an effective strategy to harvest ambient waste heat into electrical energy to tackle global energy and environmental crises. However, current pyroelectric generators are often limited by low effective power output. Herein, we develop a non-contact, solar-induced pyroelectric nanogenerator (S-PENG) which integrates Au@CNT as solar-thermal layer and polarized PVDF film as pyroelectric layer. The high thermal conductivity of CNT accelerates the heat transfer process, while its strong solar-thermal effect can be coupled with the plasmonic effect of Au nanoparticles to obtain a hybrid ensemble with superior light absorption and conversion. Notably, the solar-thermal temperature of Au@CNT/PVDF rapidly increases from 38 °C to 79.6 °C within 30 s under sunlight irradiation, with a corresponding temperature change rate reaching a maximum of 14.3 °C/s. The drastic temperature fluctuation is crucial to improve the output performance of our S-PENG. More importantly, our S-PENG successfully generates a notable 1.5 mW/m2 output power under a 200 MΩ load (at 20 ℃), thereby overcoming the performance bottleneck of traditional S-PENG designs with micro-watt power output. Our design offers a promising approach to efficiently utilize green solar energy to alleviate our demand on limited energy resources and reduce carbon footprint.

Calculating the maximum possible yield for a typical pyroelectric neutron generator

Pyroelectric crystals are heated/cooled to supply D-D/D-T fusion for the purpose of neutron generation. Enhancing the pyroelectric neutron generators (PNG) yield is one of the main goals pursued by most of the previously developed techniques/models. Here, the maximum possible neutron yield of a PNG is calculated in which a widely-used pyroelectric crystal (i.e., LiTaO3 with a diameter of 3 cm and height of 1 cm) is applied. This calculation is performed by a simulation procedure including: (1) computation of the PNG potential/current for neutron generation based on new modifications (2) simulation of the deuterium ions acceleration into the target during a thermal cycle (3) simulation of the D-D fusion interaction using the Geant4 toolkit. The results show that the maximum yield of the PNG in the ideal conditions is about 6.4× 106 neutrons per cycle. This study provides a useful approach for determining the upper limit of the expected efficiency for typical PNGs and other compact neutron generators.

Boosting solar-to-pyroelectric energy harvesting via a plasmon-enhanced solar-thermal conversion approach

Pyroelectric technology promises the potential transformation of waste heat into useful electrical energy to address the global energy and environmental crises. However, current designs suffer from low power output and the need for additional mechanical devices to drive pyroelectric conversion. Here, we introduce an efficient sunlight-triggered pyroelectric nanogenerator (S-PENG) by combining an Au@polyethylenimine modified graphene oxide (Au@rGO-PEI)-based solar-thermal layer with a PVDF pyroelectric layer. Our strategy integrates rGO’s photothermal properties and Au nanoparticles’ plasmonic effects to boost sunlight absorption for enhanced pyroelectric conversion. When S-PENG is irradiated with sunlight, solar-thermal temperature rapidly reaches ~68 °C in 30 s which is 23 °C higher than neat PVDF. The superior solar-thermal conversion consequently enables Au@rGO-PEI/PVDF to achieve a high power output of 940 μW/m2 that is up to 35-fold better than other pyroelectric devices. By further incorporating S-PENG onto rotating windmill blades, we showcase a blade-type pyroelectric generator for direct solar energy harvesting without needing external light intensity adjustment device. This unique design functions efficiently at various outdoor environments (e.g. temperature, wind, and rain), notably achieving a high power output of 2700 μW/m2 that can be stored in a capacitor (Voc, ~ 5.2 V, 300 s charging). Our work offers valuable insights for the design of next-generation S-PENG and their facile integration with other energy technologies (e.g. windmill) for concurrent electricity harvesting from different green energy sources.

Operando structure observation of pyroelectric ceramics during power generation cycle

The microscopic origin of the pyroelectric power generation using ferroelectric ceramics for energy harvesting from time-varying waste heat can be understood by conducting operando neutron diffraction measurements. The behavior of the domain orientation and lattice strain in the lead zirconate titanate-based ceramics with a tetragonal structure during the novel power generation cycle combining the electric field and the temperature change were investigated. The [001] domains and the lattice strain of the (111) plane in the direction parallel to the electric field increase in the process of simultaneous rise in the electric field and temperature and rapidly decrease in the process of the field drop. Furthermore, larger structural changes were found in the material and cycle condition, giving higher power density. The alignment of the domain orientation by the electric field and its randomization by the higher temperature during the cycle are critical features of the current power generation system.

Novel Wearable Pyrothermoelectric Hybrid Generator for Solar Energy Harvesting.

Recently, wearable energy harvesting systems have been attracting great attention. As thermal energy is abundant in nature, developing wearable energy harvesters based on thermal energy conversion processes has been of particular interest. By integration of a high-efficient solar absorber, a pyroelectric film, and thermoelectric yarns, herein, we design a novel wearable solar-energy-driven pyrothermoelectric hybrid generator (PTEG). In contrast to those wearable pyroelectric generators and thermoelectric generators reported in previous works, our PTEG can enable effective energy harvesting from both dynamic temperature fluctuations and static temperature gradients. Under an illumination intensity of 1500 W/m2 (1.5 sun), the PTEG successfully charges two commercial capacitors to a sum voltage of 3.7 V in only 800 s, and the total energy is able to light up 73 LED light bulbs. The volumetric energy density over the two capacitors is calculated to be 67.8 μJ/cm3. The practical energy harvesting performance of the PTEG is further evaluated in the outdoor environment. The PTEG reported in this work not only demonstrates a rational structural design of high-efficient wearable energy harvesters but also paves a new pathway to integrate multiple energy conversion technologies for solar energy collection.

Registration of a pulsed generation of electron beam in the nanosecond range under heating and cooling cycles of a lithium niobate crystal at atmospheric pressure

We describe here an experimental prototype designed for registration of nanosecond discharge current pulses with an amplitude of up to 600 mA and a negative/positive polarity in the air gap between the +Z surface of a pyroelectric lithium niobate crystal and a flat copper electrode during the crystal heating/cooling cycles. The experiments were carried out in air at atmospheric pressure using a cylindrical lithium niobate sample with a diameter of 13 mm and a thickness of 7 mm. With the temperature varying from 20 to 80 °C, there were registered over 50 discharge pulses for heating as well as for cooling stage. Their parameters testify to pyroelectric generation of pulsed electron beam with a current at maximum from 45 mA to 600 mA, duration of about 15 ns, rise time from 1 to 1.9 ns, and transferred charge from 0.95 to 5.7 nC.

Enhanced pyroelectric conversion of thermal radiation energy: Energy harvesting and non-contact proximity sensor

Pyroelectric generators convert temperature fluctuations into useful electrical energy. We introduce here tosylate-doped poly(3,4-ethylenedioxythiophene) (PEDOT:Tos) as a high-performance, thermal radiation absorbing electrode for polyvinylidene difluoride, a pyroelectric material of choice among flexible polymers. With the PEDOT:Tos electrode prepared by the optimal conditions established, a significant improvement in the device efficiency is realized that is anywhere between severalfold and an order of magnitude, when compared with metal and other organic electrodes. An effectiveness factor is derived and utilized here for the comparison. The fabricated pyroelectric device is utilized to charge a commercial capacitor to demonstrate thermal energy harvest. This device with PEDOT:Tos is highly sensitive to thermal radiation, producing a high voltage in response to thermal energy. This noticeable feature is utilized to demonstrate a non-contact pyroelectric proximity sensor that is powered by a finger approaching the sensor. These results bode well for the applicability of this work to self-powered devices and electronic sensors operated with thermal radiation sources.

Pyroelectrics on purpose: A perspective on generation vs harvesting

Solid-state pyroelectric heat engines that utilize the temperature and electric field dependence of electric displacement are promising for high-efficiency high-power thermal-to-electrical energy conversion. However, one of the key challenges for pyroelectric energy conversion is the inaccessibility of tunable transient heat sources for energy harvesting. This Perspective analyzes the potential of thermal waveform engineering for pyroelectric energy generation. We use the Landau-Devonshire phenomenological model to evaluate the energy conversion performance of a representative pyroelectric material coupled to (1) static heat source/sink via thermal switches, and (2) modulated heat source. Using this thermodynamic analysis, which accounts for thermal and electrical losses, we demonstrate a path toward maximizing pyroelectric energy conversion performance through purposeful thermal and electrical control.

Modeling of energy conversion concepts based on pyroelectric material

Energy recycling and harvesting are getting more attention today because of the energy resources crisis. Heat is the most common form of wasted energy and is the greatest potential source of energy scavenging.In this work, studies on the use of a pyroelectric generator placed on the brake pad are presented. A finite Element Method (FEMs) has been used to obtain 3D models of the electric response of this material under the generated heat. This application can be used to generate electric energy from wasted thermal energy to supply the electronic systems in vehicles.

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.