Thermal Energy Harvesting Research Articles

High-efficiency thermal-electric conversion enabled by water-solid triboelectric nanogenerators within a 3D pulsating heat pipe

At present, effective strategies for obtaining electric energy from harvesting and converting thermal energy have attracted great attention in the field of new energy. According to the working principle of electrostatic induction and triboelectrification, the triboelectric nanogenerators (TENGs) technology is regarded as a promising energy harvester. Herein, we propose a novel thermal-electric generator that combines a liquid-solid TENG and a 3D pulsating heat pipe (3D-PHP). The liquid-solid TENG consists of copper foil and polytetrafluoroethylene (PTFE) tubes, and 50 % deionized water is filled into the 3D-PHP. Based on phase change heat transfer, water columns in the 3D-PHP will pulsate and flow through a liquid-solid TENG, leading to the generation of electric energy. The minimum thermal resistance of this 3D-PHP with TENGs is only 0.131 K/W at a heating power of 200 W, indicating it has excellent heat transfer performance. The peak output voltage and power generated by the developed 3D-PHP generator are up to 14 V and 1.05 μW, respectively. Finally, the harvested electricity is successfully applied to power a digital thermometer. These findings will offer a promising strategy for harvesting thermal energy from electronic equipment and systems involving high-flux heat production and dissipation.

Magnetically assembled flexible phase change composites with vertically aligned structures for thermal management and electromagnetic interference shielding

Phase change material (PCM) is promising in achieving zero-energy thermal management because of its prominent thermal storage capacity and steady phase-change temperature. However, low intrinsic thermal conductivity (TC), liquid leak, and solid rigidity are long-standing bottlenecks for heat-related applications. Here, we report an innovative dual-encapsulation strategy to develop multifunctional phase change composite (FMP) with vertically aligned NdFeB@Ag arrays and styrene-ethylene-propylene-styrene (SEPS) crosslinked network in paraffin (PA). The NdFeB@Ag arrays induced by magnetic-field driven procedure can offer the consecutive/oriented highways for efficient heat-transfer, and an electric/magnetic heterostructure for electromagnetic interference shielding efficiency (EMI SE). The flexible SEPS block copolymer not only ensures the high flexibility of PCM, but also combines with oriented NdFeB@Ag arrays for dual encapsulating PA. This multifunctional FMP can achieve high TC of 2.59 W m−1 K−1, attractive EMI SE of 35.42 dB, prominent enthalpy density of 120 J g−1, and impressive Joule heating performance, together with leakage-proof, dynamic assembly, and salient charging/discharging durability. Furthermore, the FMP-supported device is demonstrated for thermal energy harvesting and utilization. This dual-encapsulation design opens a new avenue for exploiting multifunctional PCMs for thermal management, anti-EM radiation, and low-grade exhaust heat utilization.

Pyroelectric Thermal Energy Harvester Based on Sol‐Gel‐Derived PLZT Films

The present work focuses on studying the pyroelectric properties of chemical solution deposition‐grown Pb1−xLax(Zr0.4Ti0.6)O3 films on nickel substrate which are annealed at constant temperature of 650 °C with lanthanum concentrations ranging from x = 2–8% respectively. Structural studies reveal polycrystalline nature in all the PLZT films. The dielectric constant values rise from 497 to 1048 as La doping concentration rises from 2% to 6% at a constant frequency of 1 MHz, reaching a maximum value of 1048 for 6% La doping with little variation in dielectric loss between 0.03 and 0.05. As La doping level increases from 2% to 6%, the remnant (Pr) and saturation (Ps) polarization values increase from 12 to 47 μC cm−2 and 18 to 53 μC cm−2 respectively. The leakage current is found to be 2.68 × 10−8 A for 2%‐doped PZT film and it reduces to 2.94 × 10−10 A for PLZT (6% doping) film. The influence of lanthanum doping on the pyroelectric properties has been studied in detail. The value of pyroelectric coefficient (p) is varied from 240 × 10−3 to 980 × 10−3 Cm−2 K−1 and current responsivity is varied from 960 × 10−10 to 3920 × 10−10 mV−1 with the variation in lanthanum content from 2% to 6%, respectively. The promising pyroelectric results found in PLZT films encourage these films in energy applications field.

Model and Implementation of a Novel Heat-Powered Battery-Less IIoT Architecture for Predictive Industrial Maintenance

The research and management of Industry 4.0 increasingly relies on accurate real-time quality data to apply efficient algorithms for predictive maintenance. Currently, Low-Power Wide-Area Networks (LPWANs) offer potential advantages in monitoring tasks for predictive maintenance. However, their applicability requires improvements in aspects such as energy consumption, transmission range, data rate and constant quality of service. Commonly used battery-operated IIoT devices have several limitations in their adoption in large facilities or heat-intensive industries (iron and steel, cement, etc.). In these cases, the self-heating nodes together with the appropriate low-power processing platform and industrial sensors are aligned with the requirements and real-time criteria required for industrial monitoring. From an environmental point of view, the carbon footprint associated with human activity leads to a steady rise in global average temperature. Most of the gases emitted into the atmosphere are due to these heat-intensive industries. In fact, much of the energy consumed by industries is dissipated in the form of waste heat. With this scenario, it makes sense to build heat transformation collection systems as guarantors of battery-free self-powered IIoT devices. Thermal energy harvesters work on the physical basis of the Seebeck effect. In this way, this paper gathers the methodology that standardizes the modelling and simulation of waste heat recovery systems for IoT nodes, gathering energy from any hot surface, such as a pipe or chimney. The statistical analysis is carried out with the data obtained from two different IoT architectures showing a good correlation between model simulation and prototype behaviour. Additionally, the selected model will be coupled to a low-power processing platform with LoRaWAN connectivity to demonstrate its effectiveness and self-powering ability in a real industrial environment.

Spatial and Temporal Variability of Ocean Thermal Energy Resource of the Pacific Islands

A lack of natural resources drives the oil dependency in Pacific Island Countries and Territories (PICTs), hampering energy security and imposing high electricity tariffs in the region. Nevertheless, the Western Equatorial Pacific is known for its large Sea Surface Temperature (SST) and deep-sea water (DSW) temperature difference favorable for harvesting thermal energy. In this study, we selected 18 PICTs in the western Equatorial Pacific to estimate Annual Energy Production (AEP) for a 1 MW class Ocean Thermal Energy Conversion (OTEC) plant. We combined the DSW temperature from the mean in situ Argo profiles and 1 km resolution satellite SST data to estimate the thermal energy resource resolving the fine features of the island coastline. Furthermore, the twenty-year-long SST dataset was used to analyze the SST variability. The analysis showed that Equatorial islands and Southern islands have the highest inter-annual variability due to El Nino Southern Oscillation (ENSO). The power density varied from 0.26 to 0.32 W/m2 among the islands, with the lowest values found for the southernmost islands near the South Equatorial Countercurrent. Islands within the South Equatorial Current, Equatorial Undercurrent, and North Equatorial Countercurrent showed the highest values for both power density and gross power. Considering a 1 MW class OTEC plant, Annual Energy Production (AEP) in 2022 varied from 7 GWh to 8 GWh, with relatively low variability among islands near the Equator and in low latitudes. Considering the three variables, AEP, SST variability, and distance from the shore, Nauru is a potential candidate for OTEC, with a net power of 1.14 MW within 1 km from the shore.

MODELING AND OPTIMIZATION OF A PCM-BASED OCEAN THERMAL ENERGY HARVESTER FOR POWERING UNCREWED UNDERWATER VEHICLES

Abstract As oceans cover over 70% of the planet's surface, they represent a large reservoir of resources that remained vastly untapped. Uncrewed Underwater Vehicles (UUVs) are becoming key technology for ocean exploration. Ocean thermal gradient is a permanent and reliable energy source that can be used to power UUVs using phase change material (PCM)-based thermal engines. When using PCM-based thermal engines to power UUVs, there are different energy conversion stages, thermal, hydraulic, kinetic, and electrical, dependent on a wide variety of parameters. Thus, optimization of the overall energy conversion is still a challenge for powering the increasing energy demanding UUVs for long missions. The goal of this study is to propose a PCM-based ocean thermal energy harvesting system for powering float type UUVs such as the Solo II float. This reduces the cost for battery replacement and expands the float's mission time. For this purpose, we developed a model consisting of hydraulic and electrical systems, designed to provide the electrical power needed by the UUV. The hydraulic and electrical systems are implemented using MATLAB-Simulink. The model developed can provide 13.66 kJ of electrical energy, which is more than 1.5 times the energy requirement per cycle for the SOLO II float.

Predictive model using artificial neural network to design phase change material-based ocean thermal energy harvesting systems for powering uncrewed underwater vehicles

Uncrewed underwater vehicles (UUVs) significantly benefit from phase change material (PCM)-based ocean thermal energy harvesting for long mission duration. However, this technology relies on different parameters that are critical to its efficiency. Sea trials indicated that a design using this technology has lower performance than its initial specifications. This underperformance results from different factors—mainly, the UUV's trajectory, travel time, temperature fluctuations, and biofouling on the heat exchanger due to long-term underwater operations. Therefore, there exists a need to continuously monitor the ambient energy harvesting system and predict system performance for mission planning. Two major parameters that influence the energy harvesting system include the pressure inside the hydraulic accumulator and the electrical load. This work focuses on the hydraulic-to-electric energy conversion system. A combination of numerical simulation and experimental tests is used to develop a predictive model using artificial neural network (ANN) in MATLAB. 1000 data samples from a numerical model are used to train the ANN. Compared to experimental results, the ANN model predicts the designed benchtop system's total efficiency with a maximum efficiency of 51 % and an overall relative error of less than 15 %. This work will enable energy-efficient mission planning for UUVs using PCM-based ocean thermal energy harvesting.

Vertically aligned montmorillonite aerogel–encapsulated polyethylene glycol with directional heat transfer paths for efficient solar thermal energy harvesting and storage

Vertically aligned montmorillonite aerogel–encapsulated polyethylene glycol with directional heat transfer paths for efficient solar thermal energy harvesting and storage

A Compact DC-DC Converter With Pulse-Counting MPPT and Fast One-Path Self-Startup for Thermal Energy Harvesting

A Compact DC-DC Converter With Pulse-Counting MPPT and Fast One-Path Self-Startup for Thermal Energy Harvesting

Large pyroelectric energy conversion in lead scandium tantalate thin films

Non-linear pyroelectric energy harvesting using ferroelectric thin films exhibits high energy conversion, primarily due to their large breakdown field compared to bulks. Here, we report the pyroelectric energy conversion potential of lead scandium tantalate, Pb(Sc1/2Ta1/2)O3 (PST) thin film fabricated on a c-sapphire substrate using chemical solution deposition. To enable the application of high electric field and to assess the pyroelectric energy conversion performance, interdigitated electrodes were deposited on the PST thin film. A maximum harvested energy density of 9.1 J cm−3 per cycle was deduced from polarization measurements in films undergoing an Olsen cycle between 0 °C and 150 °C when the electric field was varied between 50 and 1500 kV/cm. Furthermore, PST thin films can reach up to 27 % of Carnot efficiency for a temperature interval of 10 K between 30 °C and 40 °C. This study highlights the significance of PST thin films for electro-thermal energy harvesting and promising opportunities for enhancing the conversion efficiency and power density using thin films or thin film multi-layer capacitors in the future for thermal energy harvesting.

High‐Performance Thermoelectric Fibers from Metal‐Backboned Polymers for Body‐Temperature Wearable Power Devices

AbstractMetal‐backboned polymers (MBPs), with a unique backbone consisting of bonded metal atoms, are promising for optic, electric, magnetic, and thermoelectric fields. However, the application of MBP remains relatively understudied. Here, we develop a shear‐induced orientation method to construct a flexible nickel‐backboned polymer/carbon nanotube (NBP/CNT) thermoelectric composite fiber. It demonstrated a power factor of 719.48 μW ⋅m−1 K−2, which is ca. 3.5 times as high as the bare CNT fiber. Remarkably, with the regulation of carrier mobility and carrier concentration of NBP, the composite fiber further showed simultaneous increases in electrical conductivity and Seebeck coefficient in comparison to the bare CNT fiber. The NBP/CNT fiber can be integrated into fabrics to harvest thermal energy of human body to generate an output voltage of 3.09 mV at a temperature difference of 8 K. This research opens a new avenue for the development of MBPs in power supply.

High-Performance Thermoelectric Fibers from Metal-Backboned Polymers for Body-Temperature Wearable Power Devices.

Metal-backboned polymers (MBPs), with a unique backbone consisting of bonded metal atoms, are promising for optic, electric, magnetic, and thermoelectric fields. However, the application of MBP remains relatively understudied. Here, we develop a shear-induced orientation method to construct a flexible nickel-backboned polymer/carbon nanotube (NBP/CNT) thermoelectric composite fiber. It demonstrated a power factor of 719.48 μW ⋅m-1 K-2, which is ca. 3.5 times as high as the bare CNT fiber. Remarkably, with the regulation of carrier mobility and carrier concentration of NBP, the composite fiber further showed simultaneous increases in electrical conductivity and Seebeck coefficient in comparison to the bare CNT fiber. The NBP/CNT fiber can be integrated into fabrics to harvest thermal energy of human body to generate an output voltage of 3.09 mV at a temperature difference of 8 K. This research opens a new avenue for the development of MBPs in power supply.

Optoelectronic and thermoelectric properties of Cs2PtX6 (X=Cl, Br, I) for energy conversion applications: DFT calculations

This research employs density functional theory within the WIEN2k framework to simulate Cs2PtX6 (X = Cl, Br, I) perovskites. The study focuses on assessing the structural stability and thermodynamic properties through the computation of tolerance factor and formation energies, affirming the viability of the simulated materials. Notably, this investigation reveals a direct bandgap semiconducting character of these compounds, with specific values of the bandgap of 2.9, 2.15, and 1.08 eV for Cl, Br, and I-based compositions, respectively. The analysis of optical behavior demonstrates a redshift in absorption edge and an increase in optical conductivity, correlating with the enlarging halogen size within the series. The investigation into the thermoelectric characteristics of Cs2PtX6 perovskites, which include σ and κe as well as S, PF, and ZT, underscores the potential of Cs2PtX6 perovskites for deployment in thermal energy harvesting devices. Furthermore, the mechanical behavior assessment indicates the ductile nature of studied compounds, contributing to their overall mechanical stability. This study gives a comprehensive recognition of structural, electronic, mechanical, optical, and transport characteristics of Cs2PtX6 compounds, suggesting their promise for applications in advanced materials for optoelectronic and thermoelectric devices.

Voltage Detector Integrated Circuit as Versatile Toolbox for Charge Management of Thermally Chargeable Supercapacitor

AbstractInternet of Things (IoT) is crucial for a sustainable society from the viewpoints of optimization of energy consumption and using timing, thus aiding reduced CO2 emissions. Traditional power supply methods such as batteries are impractical for driving the trillions of sensors that future systems will likely utilize for collecting extensive environmental information. Thermoelectric power generators that enable direct heat‐to‐electricity energy conversion are considered a promising power supplying technology without maintenance because thermal energy is a ubiquitous energy source. This study develops a new class of thermoelectric modules using redox‐free electrolytes—‐thermally chargeable supercapacitor (TCS)—‐with extremely high thermoelectromotive force, generating over 2 V from a temperature difference of ≈65 °C without requiring a DC‐to‐DC converter. Additionally, using a voltage detector is demonstrated to be a versatile and efficient toolbox for the charge management of TCS. Optimization of the circuit comprising the TCS module with the ultrahigh open‐circuit voltage and voltage detector enables the automatic charging of a large capacitor, which intermittently powers different devices such as a beacon, LED, piezo speaker, and motor with the desired frequency. This approach represents a significant step toward sustainable energy in the context of low‐grade thermal energy harvesting and optimized energy consumption through IoT.

Fully inkjet-printed Ag2Se flexible thermoelectric devices for sustainable power generation

Flexible thermoelectric devices show great promise as sustainable power units for the exponentially increasing self-powered wearable electronics and ultra-widely distributed wireless sensor networks. While exciting proof-of-concept demonstrations have been reported, their large-scale implementation is impeded by unsatisfactory device performance and costly device fabrication techniques. Here, we develop Ag2Se-based thermoelectric films and flexible devices via inkjet printing. Large-area patterned arrays with microscale resolution are obtained in a dimensionally controlled manner by manipulating ink formulations and tuning printing parameters. Printed Ag2Se-based films exhibit (00 l)-textured feature, and an exceptional power factor (1097 μWm−1K−2 at 377 K) is obtained by engineering the film composition and microstructure. Benefiting from high-resolution device integration, fully inkjet-printed Ag2Se-based flexible devices achieve a record-high normalized power (2 µWK−2cm−2) and superior flexibility. Diverse application scenarios are offered by inkjet-printed devices, such as continuous power generation by harvesting thermal energy from the environment or human bodies. Our strategy demonstrates the potential to revolutionize the design and manufacture of multi-scale and complex flexible thermoelectric devices while reducing costs, enabling them to be integrated into emerging electronic systems as sustainable power sources.

Extremely large Seebeck coefficient of gelatin methacryloyl (GelMA)-based thermogalvanic cells by the dual effect of ion-induced crystallization and nanochannel control

The quasi-solid state thermogalvanic cells (TGCs) have been extensively investigated due to their high Seebeck coefficient (S) and suitability for wearable power generation. However, the influence of hydrogel nanostructure on Seebeck coefficient remains underexplored. In this study, biocompatible TGCs based on gelatin methacryloyl (GelMA) are fabricated via a fast-photocrosslinking process. Moreover, guanidium chloride (GdmCl) salts are directly introduced into the TGCs to enhance the Seebeck coefficient via ion-induced crystallization in the p-type FeCN63−/FeCN64− redox system. Small angle X-ray scattering reveals controlled GelMA hydrogel mesh size adjusting the amount of GdmCl, leading to improved intermolecular interactions between the guanidium cations and GelMA polymer. The optimized p-type Seebeck coefficient reaches an unprecedented 21.6 mV K−1, which is the highest thus far reported in the context of the TGC system. Furthermore, a prototype wearable thermoelectric generator (TEG) with an output voltage of 1.6 V under a temperature difference (ΔT) of 9 °C is able to power an LED directly without requiring an additional voltage booster. In brief, the dual effect of ion-induced crystallization and nanochannel control substantially enhances the Seebeck coefficient of the TGC, thereby offering a promising strategy for enhancing the performance of low-grade thermal energy harvesting wearable TEGs.

Thermal noise energy regulation in a double-cavity magnomechanical system

We investigate the thermal transport characteristics in a double-cavity magnomechanical system with a yttrium iron garnet sphere. We explore mainly the performance parameter of the thermo-phonon flux flowing from the thermal bath of a mechanical motion into the magnomechanical system and study its dependence on the cavity field detuning and decay, the magnon-photon and magnon-phonon coupling strengths, and the Kerr nonlinear coefficient of magnon. We find that the direction and magnitude of the steady-state thermophonon flux in the magnomechanical system can be controlled flexibly by modulating these system parameters. In particular, the interference effect of quantum transitions in the multi-mode magnomechanical system results a multiple dip structure in the heat flow pattern. The results obtained her e help demonstrate the thermal noise energy harvesting and rectification by the cavity magnomechanical setup.

Harvesting Thermal Energy through Pyroelectric and Thermoelectric Nanomaterials for Catalytic Applications

The current scenario sees over 60% of primary energy being dissipated as waste heat directly into the environment, contributing significantly to energy loss and global warming. Therefore, low-grade waste heat harvesting has been long considered a critical issue. Pyroelectric (PE) materials utilize temperature oscillation to generate electricity, while thermoelectric (TE) materials convert temperature differences into electrical energy. Nanostructured PE and TE materials have recently gained prominence as promising catalysts for converting thermal energy directly into chemical energy in a green manner. This short review provides a summary and comparison of catalytic processes initiated by PE and TE effects driven by waste thermal energy. The discussion covers fundamental principles and reaction mechanisms, followed by the introduction of representative examples of PE and TE nanomaterials in various catalytic fields, including water splitting, organic synthesis, air purification, and biomedical applications. Finally, the review addresses challenges and outlines future prospects in this emerging field.

Chemically tailored biomass sponge-based hierarchical porous carbon for superior solar thermal energy harvesting and stable thermal energy storage/release

In the past work, almost all biomass sponge-based hierarchical porous carbons are tried to preserve the original 3D porous structure as much as possible, thus restricting their effectiveness in thermal energy utilization. In current work, loofah sponge-based hierarchical porous carbon covering nanometer to micrometer was fabricated through a crosslinking-carbonization-etching chemically tailored process. The re-constructed hierarchical porous carbons (LHPCs) have totally different characteristics from that depending on original 3D pores. The LHPC-based composite phase change materials (PCMs) exhibited the maximum melting/solidifying latent heat of 155.1/158.7 J g−1 and exceptional thermal reliability. The optimal solar-thermal converting efficiency of the composite PCMs topped 95 %, higher than some expensive carbon-based materials. Compared to previously reported work, the fabricated composite PCMs showed improved thermal energy storage/release capability and solar-heat conversion efficiency. Additionally, the regulation of about 6.3 °C for composite PCMs was achieved in a hut test. This work has further advanced a superior porous carbon-tailored strategy compared to the traditional approach, building upon the original 3D porous structure.

Hydraulic-driven adaptable morphing active-cooling elastomer with bioinspired bicontinuous phases

The active-cooling elastomer concept, originating from vascular thermoregulation for soft biological tissue, is expected to develop an effective heat dissipation method for human skin, flexible electronics, and soft robots due to the desired interface mechanical compliance. However, its low thermal conduction and poor adaptation limit its cooling effects. Inspired by the bone structure, this work reports a simple yet versatile method of fabricating arbitrary-geometry liquid metal skeleton-based elastomer with bicontinuous Gyroid-shaped phases, exhibiting high thermal conductivity (up to 27.1 W/mK) and stretchability (strain limit >600%). Enlightened by the vasodilation principle for blood flow regulation, we also establish a hydraulic-driven conformal morphing strategy for better thermoregulation by modulating the hydraulic pressure of channels to adapt the complicated shape with large surface roughness (even a concave body). The liquid metal active-cooling elastomer, integrated with the flexible thermoelectric device, is demonstrated with various applications in the soft gripper, thermal-energy harvesting, and head thermoregulation.