Energy Harvesting Potential Research Articles

Water-Induced Phase Separation for Anti-Swelling Hydrogel Adhesives in Underwater Soft Electronics.

The development of hydrogel-based underwater electronics has gained significant attention due to their flexibility and portability compared to conventional rigid devices. However, common hydrogels face challenges such as swelling and poor underwater adhesion, limiting their practicality in water environments. Here, a water-induced phase separation strategy to fabricate hydrogels with enhanced anti-swelling properties and underwater adhesion is presented. By leveraging the contrasting affinity of different polymer chains to water, a phase-separated structure with rich hydrophobic and dilute hydrophilic polymer phases is achieved. This dual-phase structure, meticulously characterized from the macroscopic to the nanoscale, confers the hydrogel network with augmented retractive elastic forces and facilitates efficient water drainage at the gel-substrate interface. As a result, the hydrogel exhibits remarkable swelling resistance and long-lasting adhesion to diverse substrates. Additionally, the integration of carboxylic multiwalled carbon nanotubes into the hydrogel system preserves its anti-swelling and adhesion properties while imparting superior conductivity. The conductive phase-separated hydrogel exhibited great potential in diverse underwater applications, including sensing, communication, and energy harvesting. This study elucidates a facile strategy for designing anti-swelling underwater adhesives by leveraging the ambient solvent effect, which is expected to offer some insights for the development of next-generation adhesive soft materials tailored for aqueous environments.

Stretchable Thermoelectric Fibers with Three-Dimensional Interconnected Porous Network for Low-Grade Body Heat Energy Harvesting.

Electricity generation from body heat has garnered significant interest as a sustainable power source for wearable bioelectronics. In this work, we report stretchable n-type thermoelectric fibers based on the hybrid of Ti3C2Tx MXene nanoflakes and polyurethane (MP) through a wet-spinning process. The proposed fibers are designed with a 3D interconnected porous network to achieve satisfactory electrical conductivity (σ), thermal conductivity (κ), and stretchability simultaneously. We systematically optimize the thermoelectric and mechanical traits of the MP fibers and the MP-60 (with 60 wt % MXene content) exhibits a high σ of 1.25 × 103 S m-1, an n-type Seebeck coefficient of -8.3 μV K-1, and a notably low κ of 0.19 W m-1 K-1. Additionally, the MP-60 fibers possess great stretchability and mechanical strength with a tensile strain of 434% and a breaking stress of 11.8 MPa. Toward practical application, a textile thermoelectric generator is constructed based on the MP-60 fibers and achieves a voltage of 3.6 mV with a temperature gradient between the body skin and ambient environment, highlighting the enormous potential of low-grade body heat energy harvesting.

Absorption enhancement of ultra-thin film Solar Cell using Fabry-Perot and plasmonic modes

In this paper, we investigate the photonic and plasmonic modes in order to enhance the absorption of ultrathin film Si Solar Cells. The simulations based on FEM show that these mechanisms enhance the absorption of the cell significantly. In order to investigate the plasmonic effects and use the amazing optical properties of localized surface plasmons (LSPs), multiple Au nanoparticles (NPs) with different radii have been used on the front surface of the Cell. Simulations show that the use of Au NPs with radii of 25, 50, and 75 nm simultaneously on the front surface of the Cell, increases the absorption dramatically. It is observed that multiple Au NPs with configuration illustrated in Case 5, enhance the absorption significantly due to the excitation of the multiple plasmonic modes in UV and Visible regions. In order to enhance the absorption in near-IR, we use Cu NPs on the backside of the cell. The highest average absorption of 84.7%, short-circuit current density of 36.7 (mA/cm2), and efficiency of 30.1% is achieved, with an increase of 177.7%, 178%, and 178.7% compared to Case 1, respectively. These methods promise the performance improvement of ultra-thin film solar cells and increase their application potential in Solar energy harvesting.

Iron self-diffusion in B2-FeRh thin film

Iron-rhodium thin films are in the center of scientific interest due to their great potential in spintronic, energy harvesting and other forthcoming applications. The structural stability of these materials in industrial applications relies heavily on their ability to withstand temperature variations, therefore it is crucial to gain a thorough understanding of the diffusion processes induced by temperature. To investigate the self-diffusion of iron in FeRh, an isotope-periodic multilayer structure of [nFe50.5Rh49.5(63 Å)/57Fe51.5Rh48.5(46 Å)]10 was prepared by molecular beam epitaxy. By using neutron reflectivity technique, which is capable of detecting atomic-scale diffusion lengths, we determined the pre-exponent factor and activation energy as D0 = (1.19 ± 0.5) × 10−16 m2s−1 and Ea = (1.00 ± 0.03) eV respectively.

Lead-free silver niobate microparticles-loaded PDMS composite films for high-performance clip-like hybrid mechanical energy harvesters

A triboelectric nanogenerator (TENG) is a highly potential green energy harvesting technology to power small-scale electronic devices. Enhancing the overall electricity production capacity of TENGs is a primary concern for their utilization as an electricity generator in day-to-day life. Herein, we proposed a lead-free silver niobate (AgNbO3 (ANb)) microparticles (MPs)-embedded polydimethylsiloxane (PDMS) composite film-based clip-like hybrid nanogenerator (HNG) device, producing an enhanced electrical output from the applied mechanical movements. The ANb MPs with a high dielectric constant were initially synthesized and embedded inside the PDMS polymer matrix. Various HNGs were fabricated utilizing ANb MPs/PDMS composite films/aluminum tape as negative/positive triboelectric films, respectively and operated in contact-separation mode. The electrical output from them was comparatively analyzed to investigate an optimum concentration of the ANb MPs inside the PDMS film. The robust HNG with 5 wt % ANb MPs/PDMS composite film produced the highest electrical output with promising stability. Thereafter, three similar optimized HNGs were fabricated and integrated within a 3D-printed clip-like structure and the electrical output was thoroughly evaluated while combining multiple HNGs as well as from each independent HNG. The clip-like HNG device exhibited an electrical output of 340 V and 20 µA that can be further utilized to charge various capacitors and power portable electronics. Owing to the high resilience structure of the clip-like HNG device, it was also demonstrated to harvest biomechanical energy produced by human movements into electricity. The mechanical energy harvesting when the clip-like HNG device was attached to the accelerator pedal of the car and the pedal of a musical piano was successfully demonstrated.

Sustainable Energy Harvesting Mechanism with Flow-Induced Vibration

This study investigates the feasibility of utilizing a flow-induced vibration actuator as a potential energy source using piezoelectric energy harvesting. The focus is on exploring the behavior of piezo films configured as cantilever beams subjected to flow-induced vibration, which can be induced with fluid or wind streams. The primary objective is to maximize the harvested energy from the vibrating structure. This paper develops theoretical models to analyze the resonant frequencies and energy-harvesting potential of the piezo films in the context of flow-induced vibration. Experimental validations are conducted to verify the theoretical predictions. The findings indicate that higher operating frequencies in the second mode offer improved energy harvesting efficiency compared with lower modes. With the strategic adjustment of resonant frequencies using attached masses on individual piezo films, the harvestable energy output of a single film can be significantly increased from less than 1 μW to approximately 18 μW. However, the phase differences among individual piezo films can impact frequency measurements, necessitating careful fine-tuning of the physical conditions of individual components. To optimize energy harvesting, this study emphasizes the importance of implementing efficient charging mechanisms. By identifying suitable environmental vibration sources, the required charging duration for a synthesized energy harvesting array can be reduced by 25% as well. Despite certain challenges, such as phase deviations and turbulence, this study demonstrates the promising potential of flow-induced vibration resonators as sustainable energy sources. This work lays the foundation for further advancements in energy harvesting technology, offering environmentally friendly and renewable energy solutions.

A High-Performance Circularly Polarized and Harmonic Rejection Rectenna for Electromagnetic Energy Harvesting.

This paper presents a novel circularly polarized rectenna designed for efficient electromagnetic energy harvesting at the 2.45 GHz ISM band. A compact antenna structure is designed to achieve high performance in terms of radiation efficiency, axial ratio, directivity, effective area, and harmonic rejection over the entire bandwidth of the ISM frequency band. The optimized rectifier circuit enhances the RF harvested energy efficiency, with an AC-to-DC conversion efficiency ranging from 36% to 70% for low-level input power ranging from -10 dBm to 0 dBm. The stable output of DC power confirms the suitability of this design for various practical applications, including wireless sensor networks, energy harvesting power supplies, medical implants, and environmental monitoring systems. Experimental validation, which includes both the reflection coefficient and radiation patterns of the designed antenna, confirms the accuracy of the simulation. The study found that the proposed energy harvesting system has a high total efficiency ranging from 53% to 63% and is well-suited for low-power energy harvesting (0 dBm) from ambient electromagnetic radiation. The proposed circularly polarized rectenna is a competitive option for efficient electromagnetic energy harvesting, both as a standalone unit and in an array, due to its high performance, feasibility, and versatility in meeting various energy harvesting requirements. This makes it a promising and cost-effective solution for various wireless communication applications, offering great potential for efficient energy harvesting from ambient electromagnetic radiation.

On spatial interpolation of ocean energy source variables: A comparative analysis

In the context of wave energy systems development, the estimation of wave parameters such as significant wave height (Hs) and energy period (Te) over the entire ocean surface is of paramount importance. These information are crucial for estimating the energy harvesting potential of deployment sites, designing wave energy converters (WECs), planning optimal maintenance intervention frequency, and assessing the impact of waves on coastal communities. However, measuring Hs and the Te at every point in the ocean is impossible due to the vastness of the ocean and due to the cost and difficulties of installing and maintaining wave instrumentation buoys, since these have to survive in marine environment, which is particularly hostile. As a consequence, the amount of data is too limited and sparse in space for the practical and precise performance of these analyses. To address such data scarcity and sparsity, we analyse in this paper various spatial interpolation techniques employed to fill the spatial gaps in the wave parameter datasets. These techniques are compared in their performances in estimating the wave parameters in space given a set of known measurements in limited sampling locations. Three types of interpolators are considered: linear interpolator, spline interpolator, and radial basis functions (RBFs) interpolator. These algorithms are trained and tested on a public dataset of wave parameters from Copernicus Marine Service in an area between the coastlines of South England and North France. To simulate the available data scarcity and sparsity, only limited percentages of the ocean area are considered covered and available in the training stage (from 0.01% to 1%). The performance of each interpolator is evaluated on the remainder of the considered area in terms of Normalized Root Mean Square Error (NRMSE) and on the Normalized Mean Absolute Error (NMAE) achieved by the algorithm in reconstructing the parameters at these unsampled locations. The results of this study demonstrate the feasibility of spatial gap-filling of wave parameters, and demonstrates that the RBF algorithm outperforms the other two algorithms both in performances and, even more, in terms of robustness to different training points sampling.

Enhanced UV Absorption By 2D MoS2 Nanoparticles

MoS2 is one of the promising 2D materials that caught the interest of many research fields[1], [2] due to their size-dependent tunable bandgap and attractive magnetic, optical, and electrical properties[3]. Furthermore, recently there has been a growing interest in utilizing MoS2 for solar cell applications that demonstrated measurable device enhancements[4]–[6]. Hence, there is a great interest in understanding its potential for solar energy harvesting. In this study, we show a simple method to deposit a 2D layer of MoS2 nanoparticles (NPs) on top of Aluminum-doped Zinc oxide (AZO) layer (transparent conductive oxide) and investigate its spectral response and potential for application in optoelectronic systems.A thin film of 80 nm AZO layer was grown on a 4-inch quartz wafer using thermal Atomic Layer Deposition (ALD) with a 1:19 ratio which has shown good electrical and optical qualities for solar cell applications[7]. We deposited the MoS2 by spin-coating it on the AZO/quartz wafers for 40 sec at 1000 rpm. Incremental coating is carried on by dispersing seven layers with 500 μL of MoS2 in each step using a precise pipet to a cumulative dispersion volume of 3500 μL. The prepared samples were characterized using a UV-Vis-NIR spectrometer (Perkin Elmer Lambda) across a wide range of wavelengths (250-1200 nm) by measuring both transmittance and reflectance and calculating absorbance. Furthermore, the base AZO/quartz and quartz background signal were measured before spin-coating as reference.The obtained data shows a high absorbance effect due to MoS2 NPs at low wavelengths (<400 nm), where it peaks around 340 nm with an approximate absorbance of ~6.7%. Upon further examination, we notice that this behavior is not linear across the whole spectrum and instead is a function of (i) wavelength and (ii) MoS2 quantity which could be partially due to the quantum confinement effect of several layers of stacked 3D MoS2 nanoparticles[8]. This phenomenon could open the possibility of utilizing this material for low-wavelength filters or UV sensing applications[9]. Also, it can potentially be utilized for quantum down-conversion[10] of high-energy photons to re-emit photons at lower energies in order to enhance solar cells’ efficiencies and reduce thermal burden; however, further investigation is needed.[1] P. Zhou, C. Chen, X. Wang, B. Hu, and H. San, “2-Dimentional photoconductive MoS2 nanosheets using in surface acoustic wave resonators for ultraviolet light sensing,” Sensors and Actuators A: Physical, vol. 271, pp. 389–397, Mar. 2018, doi: 10.1016/j.sna.2017.12.007.[2] H. Dong et al., “Fluorescent MoS 2 Quantum Dots: Ultrasonic Preparation, Up-Conversion and Down-Conversion Bioimaging, and Photodynamic Therapy,” ACS Appl. Mater. Interfaces, vol. 8, no. 5, pp. 3107–3114, Feb. 2016, doi: 10.1021/acsami.5b10459.[3] K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, “Atomically Thin MoS 2 : A New Direct-Gap Semiconductor,” Phys. Rev. Lett., vol. 105, no. 13, p. 136805, Sep. 2010, doi: 10.1103/PhysRevLett.105.136805.[4] Y. Tsuboi et al., “Enhanced photovoltaic performances of graphene/Si solar cells by insertion of a MoS 2 thin film,” Nanoscale, vol. 7, no. 34, pp. 14476–14482, 2015, doi: 10.1039/C5NR03046C.[5] N. A. Abd Malek et al., “Ultra-thin MoS2 nanosheet for electron transport layer of perovskite solar cells,” Optical Materials, vol. 104, p. 109933, Jun. 2020, doi: 10.1016/j.optmat.2020.109933.[6] Y.-J. Huang, H.-C. Chen, H.-K. Lin, and K.-H. Wei, “Doping ZnO Electron Transport Layers with MoS 2 Nanosheets Enhances the Efficiency of Polymer Solar Cells,” ACS Appl. Mater. Interfaces, vol. 10, no. 23, pp. 20196–20204, Jun. 2018, doi: 10.1021/acsami.8b06413.[7] S. Abdul Hadi, G. Dushaq, and A. Nayfeh, “Effect of atomic layer deposited Al 2 O 3 :ZnO alloys on thin-film silicon photovoltaic devices,” Journal of Applied Physics, vol. 122, no. 24, p. 245103, Dec. 2017, doi: 10.1063/1.4990871.[8] T. Li and G. Galli, “Electronic Properties of MoS 2 Nanoparticles,” J. Phys. Chem. C, vol. 111, no. 44, pp. 16192–16196, Nov. 2007, doi: 10.1021/jp075424v.[9] Z. Lou et al., “High-performance MoS_2/Si heterojunction broadband photodetectors from deep ultraviolet to near infrared,” Opt. Lett., vol. 42, no. 17, p. 3335, Sep. 2017, doi: 10.1364/OL.42.003335.[10] A. P. Sunitha, P. Praveen, M. K. Jayaraj, and K. J. Saji, “Upconversion and downconversion photoluminescence and optical limiting in colloidal MoS2 nanostructures prepared by ultrasonication,” Optical Materials, vol. 85, pp. 61–70, Nov. 2018, doi: 10.1016/j.optmat.2018.08.038.[11] Y. Wu et al., “Monolithic integration of MoS 2 -based visible detectors and GaN-based UV detectors,” Photon. Res., vol. 7, no. 10, p. 1127, Oct. 2019, doi: 10.1364/PRJ.7.001127. Figure 1

Enhanced Lifetime of Cyanine Salts in Dilute Matrix Luminescent Solar Concentrators via Counterion Tuning.

Organic luminophores offer great potential for energy harvesting and light emission due to tunable spectral properties, strong luminescence, high solubility, and excellent wavelength-selectivity. To realize their full potential, the lifetimes of luminophores must extend to many years under illumination. Many organic luminophores, however, have a tendency to degrade and undergo rapid photobleaching, leading to the perception of intrinsic instability of organic molecules. In this work we demonstrate that by exchanging the counterion of a heptamethine cyanine salt the photostability and corresponding lifetime of dilute cyanine salts can be enhanced by orders of magnitude from 10 hours to an extrapolated lifetime of greater than 65,000 hours under illumination. To help correlate and comprehend the underlying mechanism behind this phenomenon, the water contact angle and binding energy of each pairing were measured and calculated. We find that increased water contact angle, and therefore increasing hydrophobicity, generally correlate to improved lifetimes. Similarly, a lower absolute binding energy between cation and anion correlates to increased lifetimes. Utilizing the binding energy formalism, we predict the stability of a new anion and experimentally verify with good consistency. Moving forward, these factors could be used to rapidly screen and identify highly photostable organic luminophore salt systems for a range of energy harvesting and light emitting applications.

Near-field radiative modulator based on α-MoO3 films

Near-field radiative heat transfer (NFRHT) has great potential in thermal management and energy harvesting due to the giant radiative heat flux. Modulation of NFRHT is another important research direction, where relative rotation between the emitter and receiver is a typical method. However, the enhancement of modulation contrast (MC) is mainly concerned in previous works, while large heat flux is not taken into account. In this work, we investigate the heat transfer coefficient (HTC) between α-MoO3 films along different crystal directions of α-MoO3. We take account of the modulator with high heat flux and high MC. The results show that the HTC and MC can reach 223.2 W/(m2·K) (36 times of blackbody limit) and 6.33 at a gap distance of 100 nm when NFRHT is along [010] crystal direction of α-MoO3, respectively. These are attributed to the excitation and mismatch of hyperbolic phonon polaritons (HPhPs). Furthermore, when NFRHT is along [100] and [001] crystal directions of α-MoO3, MCs reach 5.84 and 2.38, respectively. The results are strongly related to the crystal direction. In addition, the impact of film thickness on the MC for different crystal directions is investigated. This work is conducive to the applications of hyperbolic materials in non-contact thermal modulators.

Real-time Thermal Energy Harvesting from Solar Radiation in Malaysia at Low-Temperature Difference

.Malaysia is located in a tropical climate with an abundance of solar radiation. Due to the low albedo of roofing material, around 20 % to 90 % of heat is absorbed from solar radiation. Thus, it is possible to harvest thermal energy from solar radiation using TEG, which promotes the diversity of renewable energy sources in Malaysia. Previous research evaluates the potential of thermal energy harvesting of the TEG open circuit voltage and unipolar condition. Thereby, this research focuses on designing and developing a thermal energy harvesting system (TEHS) for harvesting thermal energy at low-temperature differences from solar radiation. The TEHS can harvest thermal energy in bipolar conditions, different voltage levels, TEG input voltage fluctuations, and rapid weather-changing conditions during real-time field tests. Parallel with series balance TEG array configuration obtained impedance matching at 125 Ω. The field test method was conducted for 105 days. The maximum mean efficiency obtained is 94.33 %, with an output power range between 0.46 mW and 66.10 mW. The promising finding indicates that the developed TEHS is robust and capable of operating at optimum power transfer at uncontrollable solar radiation and weather conditions. In addition, the potential of the power generated evaluation is to be used as a power supply to several sensor nodes.

Design of Solar Collector Prototype with Working Fluid Temperature and Pressure Measurement for Energy Harvesting

Indonesia is a tropical country, which gets a lot of sunshine every year. Harvesting energy from solar heat is an alternative solution to obtain renewable and environmentally friendly electrical energy. The purpose of this research is to design and test the temperature and flow of the working fluid of a solar collector for energy harvesting. The method used is true experiment research by making a solar collector prototype. Measurement of the temperature and pressure of the working fluid is carried out by varying the power of the heating lamp as a substitute for sunlight in the test. The experimental results show that the greater the heat energy received by the solar collector, the higher the temperature of the working fluid and the resulting pressure during the same test. The highest temperature recorded for the liquid coming out of the solar collector reaches 63.6 oC with a maximum pressure difference of 19.6 Pascals. The results of this test will be followed by testing the flow rate of the working fluid to determine the power potential of the working fluid for harvesting energy.&#x0D; Highlights:&#x0D; &#x0D; Efficiency Enhancement: Optimizing solar collector design for increased heat energy absorption and efficient energy conversion.&#x0D; Temperature-Pressure Correlation: Investigating the relationship between heat energy, working fluid temperature, and pressure for better energy yield.&#x0D; Flow Rate Analysis: Assessing working fluid flow to gauge energy potential and inform effective energy harvesting strategies.&#x0D; &#x0D; Keywords: solar collector, temperature, fluid pressure, energy harvesting

Two-Port Five-Band Rectenna for Ultralow Ambient RF Energy Harvesting

A two-port rectenna is proposed to harvest the ambient RF power from five commercial bands, including 1.8 GHz, 2.1 GHz, 2.4 GHz, 2.65 and 3.5 GHz for GSM, LTE, WLAN and 5G, respectively. The novel rectenna comprises a hybrid half-wave rectifier and two back-to-back slot antennas. The rectifier consists of a series rectifier branch and a parallel rectifier branch to extend its multi-band coverage, only sharing one diode. With this design strategy, its RF-DC power conversion efficiency (PCE) can reach 23.1% at 1.8 GHz, 26.4% at 2.1 GHz, 27.2% at 2.4 GHz, 20.7% at 2.66 GHz and 19.1% at 3.47 GHz with -20 dBm input power level. Notably, once a five-tone signal is input simultaneously with the identical power level of -20 dBm, the PCE of rectifying circuit can be improved to 43.7%, breaking the existing record to our best knowledge. The designed slot antennas can also receive omnidirectional RF power at five corresponding frequencies. The experimental results demonstrate that our proposed rectenna is competitive in band coverage and PCE with ultra-low input power, indicating enormous potential for RF energy harvesting and powering sensors, wearables, and other low-power scenarios.

Hydrovoltaic energy from water droplets: Device configurations, mechanisms, and applications

AbstractWater, the source of life, contains immense energy and manifests in diverse forms. Hydrovoltaic technology enables the direct interaction between water and materials to generate electricity, a vital necessity for industry modernization. Due to the ubiquitous presence and easy availability of falling water, hydrovoltaic energy derived from water droplets has attracted considerable attention and shown great potential in raindrop energy harvesting. In this review, a comprehensive summary of the latest advancements in harvesting hydrovoltaic energy from water droplets is presented, with a focus on the configurations and underlying mechanisms of hydrovoltaic devices. Additionally, a brief discussion on the applications of droplet‐based hydrovoltaic devices is presented, along with future prospects for this energy‐harvesting technology.

Electrospun nanofibers doped with PVDF and PLZT nanoparticles for potential biomedical and energy harvesting applications

Electrospun nanofibers doped with PVDF and PLZT nanoparticles for potential biomedical and energy harvesting applications

LES study on the urban wind energy resources above the roof of buildings in generic cluster arrangements: Impact of building position

Urbanisation brought an increasing prevalence of groups of high-rise buildings and raised new questions about their impact on local wind flow conditions and the wind energy harvesting potential. The focus of this study is two-fold. First, it gives insight into the interference effects around high-rise buildings based on the level of building exposure to the wind and the position of surrounding buildings. Second, it addresses wind energy resources above the roof in terms of the Wind Power Density (WPD), turbulence intensities and skew angle.Three study cases are defined from two configurations: The isolated high-rise building and the group configuration of five identical buildings in two different arrangements. Two wind directions are included, 0°and 45°. Validated large-eddy simulations are used due to their superior simulation capabilities.The strongest separation around the building is noted in the group configuration when the two upstream buildings produce the “channelling effect” and with other surrounding buildings compress the flow around the central one. Regarding wind energy harvesting, maximal value of 2.5 is recorded at 45°wind angle in the “cross” shape arrangement. Considering the different wind turbine types, vertical-axis wind turbines seem the most promising option for wind energy harvesting above the roof.

Numerical Assessment of Flow Energy Harvesting Potential in a Micro-Channel

A micro-energy harvesting device proposed in the literature was numerically studied. It consists of two bluff bodies in a micro-channel and a flexible diaphragm at its upper wall. Vortex shedding behind bodies induces pressure fluctuation causing vibration of the diaphragm that converts mechanical energy to electrical by means of a piezoelectric membrane. Research on enhancing vortex shedding was justified due to the low power output of the device. The amplitude and frequency of the unsteady pressure fluctuation on the diaphragm were numerically predicted. The vortex shedding severity was mainly assessed in terms of pressure amplitude. The CFD model set-up was described in detail, and appropriate metrics to assess the energy harvesting potential were defined. Several 2D cases were simulated to study the effect of the inlet Reynolds number and channel blockage ratio on the prospective performance of the device. Furthermore, the critical blockage ratio leading to the vortex shedding suppression was sought. A higher inlet velocity for a constant blockage ratio was found to enhance vortex shedding and the pressure drop. Great blockage ratio values but lower than the critical ones seemed to provide great pressure amplitudes at the expense of a moderate pressure drop. There is evidence that the field is fruitful for further research and relevant directions were provided.

Thermoelectric converter with stepwise legs for high energy conversion efficiency

Due to industrial activity, an enormous amount of heat is wasted on the environment enabling energy loss and global warming. Thermoelectric (TE) technologies make possible the direct conversion of waste heat into electrical energy. The main bottlenecks of energy conversion by TE devices are low efficiency as well as the expensive and complex fabrication procedure of industrial converters. In this work, we fabricated a Bi2Te3-based TE converter with stepwise legs for highly efficient energy conversion using a single-step sintering method. Before the fabrication of the converter, we employed the numerical simulation and found that Co is the best choice among the other well-established metallic layers, that can be used for the highly conductive covering of the n- and p-type TE legs. The employment of this metal produces the lowest thermal stress that occurs in the stepwise converter at the cooling stage of a sintering process. The energy conversion efficiency of the designed converter estimated using the finite element method reaches 10.1% at a temperature difference of 375 K (Tc = 300 K). Moreover, the measured value of efficiency achieves 8.5%, which is 1.4 times higher than the commercial Bi2Te3-based converters and 9–14% higher than the other reported stepwise converters. The enhanced efficiency mainly originates from the effective stepwise design of the n- and p-type TE legs. This work offers a new path for the simple single-step fabrication of the Bi2Te3-based TE converters that should have great potential for energy harvesting.

Flexible stretchable tribo-negative films with exceptional output performance for high-temperature energy harvesting and self-powered sensor

High temperature is a significant cause of failure of electromechanical products, achieving effective collection of triboelectric energy at high-temperatures is a major research emphasis. Improving the electrical outputs from triboelectric nanogenerator (TENG) in extreme environments is crucial for its large-scale application and remains challenging. Further considering the major potential application for TENG is wearable electronics, a series of SEBS/fatty acid (SEBS/FA) skin-like flexible films were fabricated, which exhibit adjustable surface triboelectricity and enhanced triboelectric outputs at high-temperatures. The SEBS/FA based TENGs possess remarkable durability of over 10,000 contact-separation cycles, and exhibit exceptional electrical outputs in the heat. Thereinto, the output efficiency of SEBS-OA (octanoic acid) is up to 302.32 % at 110 °C and still above 100 % at 150 °C. The SEBS/FA based TENGs can efficiently harvest the mechanical energy in high-temperature environments to power commercial capacitors and LEDs. Notably, the SEBS/FA films still show enhanced electrical outputs even under extreme conditions with working ambient temperatures up to 90 °C and significant deformation (λ ≤ 4). The excellent electromechanical performances enable SEBS/FA based TENGs to be served as flexible energy collector and self-powered touch sensor for motion capture. The real-time tactile trajectory can be accurately mapped by a 5 × 5 sensing array. The SEBS/FA films exhibit great potential in energy harvesting and active real-time tactile sensing system in extreme environments.