Harvesting Performance Research Articles

Ultra-low frequency vibration energy harvesting of piezoelectric vibration systems with an adjustable device

Energy harvesting from external Ultra-low frequency vibrations is currently attracting a lot of attention. However, for the same system, it is difficult to satisfy the need for more efficient energy harvesting in a variety of external environments. Accordingly, an adjustable gearing device connected to the energy harvesting system is used herein for adapting energy harvesting to a wide range of external environments. The device uses four symmetrical inclined springs. One end of the springs is connected to a gear and the other end to a mass element. The geometrical parameters of the system can be varied by rotating the gears, thus varying the dynamic stiffness of the system. The kinetic equations of the system are derived and their nonlinear terms are Taylor-expanded. The amplitude-frequency response curve of the system is obtained by solving using the harmonic balance method. Multi-color plots of RMS values of induced voltage and electric power are obtained using the fourth-order Runge-Kutta method. The results show that the device has excellent adjustable performance. Adjusting the rotation angle of the gears can change the soft and hard characteristics of the system's dynamic stiffness and the intrinsic frequency, thus improving the system's energy harvesting performance in different environments.

Enhancing cold energy harvest with daytime passive radiative cooling and phase change materials integration: A numerical exploration

Daytime passive radiative cooling (DPRC) is an emerging technology to dissipate heat to the ultimate cold sink, the universe, with zero energy input. However, the achieved cold surface temperature of an object by DPRC can readily increase close to the ambient temperature. Sensible heat readily induces changes in the temperature of objects, but it generates a heat leakage path to surroundings with the largely varying temperature gradients. To address the challenge, we designed a DPRC coating integrated with phase change materials (PCM) so as to harvest and store the cold energy, respectively from the universe. To evaluate the feasibility of this concept, a numerical model, which integrates a self-programmed MATLAB code to calculate the net cooling power and a FLUENT-assisted enthalpy-porosity method to simulate the phase change process, was developed and validated. Also, the cold energy harvesting performance of the proposed device was explored under different climate types and conditions. We found that the surface temperature of the PCM with a DPRC coating can be reduced to −15.9 °C and −4.5 °C in a day in the temperate continental climate and the subtropical desert climate, respectively, when the non-radiative heat transfer is completely avoided. The temperature difference in the PCM is less than 1.0 °C when aluminum fins are added to enhance the heat transfer performance of the PCM. This study provides new insights into the continuous steady cooling of DPRC using PCMs, and the harvested cold energy can be used to cool water for the condenser of an air conditioner to save energy consumption.

Improving Output Power of a Torsional-Flutter Harvester in Stochastic Thunderstorms by Duffing - Van Der Pol Restoring Torque

Abstract Wind energy harvesters are usually designed to operate in the low wind speed range. They rely on smaller swept areas, as a complement to larger horizontal-axis wind turbines. A torsional-flutter-based apparatus is investigated herein to extract wind energy. A nonlinear hybrid restoring toque mechanism, installed at equally spaced supports, is used to produce energy through limit-cycle vibration. Energy conversion and storage from the wind flow are enabled by eddy currents. The apparatus is used during thunderstorm outflows to explore the efficiency in non-ideal wind conditions. The thunderstorm flow model accounts for both non-stationary turbulence and slowly varying mean speed, replicating thunderstorm's intensification and decay stages. This paper evolves from a recent study to examine stochastic stability. More Specifically, the output power is a random process that is derived numerically. Various thunderstorm features and variable apparatus configurations are evaluated. Numerical investigations confirm the detrimental effect of non-ideal, thunderstorms on harvester performance with, on average, an adverse increment of operational speed (about +30\%). Besides nonlinear damping, the benign flutter-prone effect is controlled by the square of the flapping angle. Since flapping amplitudes are moderate at sustained flutter, activation of the apparatus is delayed and exacerbated by the non-stationary outflow and aeroelastic load features. Finally, efficiency is carefully investigated by quantification of output power and “quality factor”.

Experimental and simulation of a tension-like nonlinear piezoelectric energy harvester

This article proposes a low-frequency and efficient tension-like nonlinear piezoelectric energy harvester, which increases the harvesting performance of the harvester by swinging the support frame. Firstly, design the structure of the harvester and draw a physical model. Secondly, finite element models are used to simulate and analyze the structure’s dynamic characteristics. Finally, make an experimental prototype of the harvester and explore the power generation characteristics of the device through experiments. The results indicate that the harvester has two natural frequencies under low-frequency conditions. The energy harvester has the optimal external resistance to achieve peak output power. The greater the excitation acceleration, the greater the total output power value of the energy harvester. When the mass of the mass block is 3.7 g and the excitation acceleration is 0.4 g, the total output power value of the energy harvester is 3.88 mW, and the harvesting frequency band is wide, indicating excellent output performance of the harvester. The experimental results of the energy harvester device are consistent with the simulation results, fully verifying the correctness of the experiment and simulation. This piezoelectric energy harvester can efficiently harvest vibration energy at low frequencies, providing a good prospect for supplying power to microelectronic devices.

Lead-free dual-frequency ultrasound implants for wireless, biphasic deep brain stimulation

Ultrasound-driven bioelectronics could offer a wireless scheme with sustainable power supply; however, current ultrasound implantable systems present critical challenges in biocompatibility and harvesting performance related to lead/lead-free piezoelectric materials and devices. Here, we report a lead-free dual-frequency ultrasound implants for wireless, biphasic deep brain stimulation, which integrates two developed lead-free sandwich porous 1-3-type piezoelectric composite elements with enhanced harvesting performance in a flexible printed circuit board. The implant is ultrasonically powered through a portable external dual-frequency transducer and generates programmable biphasic stimulus pulses in clinically relevant frequencies. Furthermore, we demonstrate ultrasound-driven implants for long-term biosafety therapy in deep brain stimulation through an epileptic rodent model. With biocompatibility and improved electrical performance, the lead-free materials and devices presented here could provide a promising platform for developing implantable ultrasonic electronics in the future.

Laser-Printed Photoanode: Femtosecond Laser-Induced Crystalline Phase Transformation of WO3 Nanorods for Space-Efficient and Flexible Thin-Film Solar Water-Splitting Cells.

Despite its potential for clean hydrogen harvesting, photoelectrochemical (PEC) water-splitting cells face challenges in commercialization, particularly related its harvesting performance and productivity at an industrial scale. Herein, a facile fabrication method of flexible thin-film photoanode for PEC water-splitting to overcome these limitations, based on laser processing technologies, is proposed. Laser-induced graphene, a carbon structure produced through direct laser writing carbonization (DLWC), plays a dual role: a flexible and stable current collector and a substrate for the hydrothermal synthesis of tungsten trioxide (WO3) nanorods (NRs). To facilitate water-splitting, a femtosecond-pulsed laser (fs laser) is focused on the WO3 NRs, converting their crystalline phase from pristine orthorhombic to monoclinic structure without thermal damage. With NiFe layered double hydroxide (LDH) catalyst, the flexible thin-film photoanode exhibits good PEC performance (1.46mAcm-2 at 1.23 VRHE) and retains ≈90% of its performance after 3000 bending cycles. With its excellent mechanical properties, the flexible photoanode can be operated in various shapes with different curvatures, enabling space-efficient PEC water-splitting by loading larger photoanode within a given space. This study is expected to contribute to the advancement of large-scale solar water-splitting cells, introducing a new approach to enhance H2/O2 production and expand its application range.

Cactus-inspired moisture harvesting for sustainable and efficient high salinity desalination

Water scarcity has become a global issue that needs to be addressed urgently. Solar steam generation (SSG) is a promising technology to alleviate the water crisis through desalination and condensation. However, the stability and efficiency of SSG can be seriously impacted by salt accumulation after prolonged operation. Common salt rejection schemes are only applicable for low-salinity (<10 wt%) desalination. In this work, inspired by the cactus's fog-capturing feature, the atmospheric water harvesting (AWH) function is integrated by an interlocked braided fibrous framework (IBFF) to absorb moisture for sustainable salt dilution during high salinity (20 wt%) desalination. The loop-pile density/height of IBFF is regulated to mimic the cactus roots/spines with different architectures, thus optimizing the water absorption/moisture harvesting performance. The excellent moisture-induced salt dilution ability ensures efficient and sustainable high salinity desalination performance over cyclic operation, with an exceptional evaporation rate of up to 3.11 kg m−2·h−1 under 1 sun radiation. Overall, this new approach offers a practical possibility for durable and competitive high salinity desalination with a continuous water/moisture supply.

Chinese architecture inspired smart roof tile integrating radiation cooling, water harvesting, and energy recycling

The development of new materials for resource and energy recycling has emerged as a primary focus in addressing global energy and environmental sustainability challenges. Inspired by traditional Chinese architecture, a smart roof tile (SRT) is scientifically designed, which incorporates hierarchical micro-nanostructured polyethylene/silica/barium sulfate composites (IH-PSB), semiconductor power generation modules, and LED chips. Leveraging the combined effects of surface and interface functionalities, the IH-PSB demonstrates exceptional sub-ambient cooling capabilities, resulting in its surface and bottom temperature being 5.4 °C and 12.1 °C lower than the ambient temperature, respectively. Additionally, the precisely controlled heterogeneous wettability, with a contact angle of approximately 151° and a roll-off angle of around 32°, allows the IH-PSB to efficiently condense moisture and transport droplets. Benefiting from the excellent radiation cooling performance and precisely controlled heterogeneous wettability, the IH-PSB exhibits remarkable passive sub-dewpoint cooling efficiency coupled with efficient water harvesting performance. During a one-month outdoor experiment, the IH-PSB operated stably and continuously without any electrical input, maintaining a mass flux ranging from ∼23.2–50.0 g m−2 h−1. Interestingly, the SRT system efficiently harnesses waste heat generated by the LEDs while simultaneously regulating their temperature effectively. The development and utilization of the SRT offer a sustainable, energy-efficient, and forward-thinking solution that addresses global water scarcity and energy crises.

Solar-powered porous polymer materials-enabled rapid atmospheric water harvesting and storage of liquid water

Atmospheric water harvesting (AWH) is emerging as a promising strategy to produce fresh water from abundant airborne moisture to reduce the global clean water shortage. Hydrogels are considered attractive adsorbents due to their higher water retention and tunable polymer-water interactions. Here, we report the super hygroscopic polymer material (SHPMs) using modified NH2-MIL-101(Cr) as a functional crosslinker by copolymerization with acrylic acid and 2-Acrylamide-2-methylpropanesulfonic acid, achieving a water uptake of about 28.8–49.7 mg/g at 28–38 % RH. The material can desorption quickly under sunlight, and the desorbed water can be stored in a polymer skeleton for use by vegetation or crops during periods of water demand. Besides, the Water retention and storage performance and its outdoor experiment also proved that the application of this material in agriculture, forestry and desertification control laid the foundation to improve the effective availability of soil moisture and water harvesting and conservation. With its excellent water retention and atmospheric water harvesting performance, the material offers a sustainable method for rapid water extraction in arid climates.

Improving the output performance of magnetic energy harvesters through coupling beam

We propose a novel magnetic energy harvester (MEH) with multiple resonance modes. The MEH consists of low-frequency and high-frequency piezoelectric cantilevers connected by a coupling beam. Theoretical modeling, simulation, and experiments were conducted to validate the multiple resonance phenomenon. The results from these investigations are consistent with each other. It is evident that the internal coupling (IC) effect resulting from the coupling beam facilitates significant voltage outputs from both cantilevers at their respective resonant frequencies, i.e. the low-frequency beam (LFB) resonates at the resonant frequency of the high-frequency beam (HFB), resulting in a remarkable 122% increase in the output voltage. Conversely, the HFB resonates at the resonant frequency of the LFB, leading to an astounding 1200% increase in the output voltage. As a result of the IC phenomenon, the operating frequency bandwidth for harvesting an output voltage of more than 1 V in the LFB has been extended by 35.3%, while that of the HFB for capturing an output voltage of more than 0.5 V has been extended by 62.5%. Additionally, the coupling effect significantly enhances the power output of the MEH.

Piezo stack energy harvesters with protection components for railway applications

Piezo stack energy harvesting from railway vibrations shows substantial potential for powering wireless sensor networks responsible for monitoring railway infrastructure. Nevertheless, assuring the safety and durability of these energy harvesters in the condition of the dynamically fluctuating railway vibrations remains a considerable challenge. In this paper, we present two innovative protection methods designed for piezo stack energy harvesters with a frequency up-conversion mechanism. These methods involve the incorporation of ring-type and circular stoppers within the resonant system and the utilisation of proposed impact protection components within the impact system. Two distinct harvesters incorporating the proposed protection components, Harvester Types I and II, are designed to align with their respective operating acceleration targets, which are determined based on the amplitudes of railway vibration acceleration. Finite element modelling is used to guide the design process, involving the evaluation and selection of various design parameters aligned with the acceleration target and stress limits. The protection mechanisms’ effectiveness and impact on energy harvesting performance have been validated through experimental testing under measured rail vibration signals, and their performance has been further assessed through stress analyses. Harvester Type I operates seamlessly within a 5 g threshold, effectively mitigating the increase in maximum output acceleration and stress beyond this limit. In contrast, Harvester Type II efficiently dissipates excess energy, enabling the harvester to operate at a 15 g acceleration while reducing the rate of acceleration and stress growth. The results demonstrate that both proposed harvesters provide effective protection from unexpected railway vibration overloads. This research makes a significant impact on the practical, real-world implementation of piezo stack energy harvesters operating within the dynamic environment of railway vibrations.

Snap-through dynamics of buckled flexible filaments in a side-by-side configuration

The flow-induced snap-through dynamics of side-by-side buckled flexible filaments in a uniform flow were investigated using the penalty immersed boundary method. We systematically examined the effects of gap distance and bending rigidity on the filament's motion and energy harvesting performance. Four distinct modes were observed as we varied the aforementioned parameters: the dual equilibrium mode, the dual streamwise oscillation mode, the single snap-through oscillation (STO) mode, and the dual STO mode. We analyzed the corresponding wake patterns associated with each of these modes. A phase transition from out-of-phase to in-phase motion was observed at low gap distances and bending rigidities. At lower gap distances, the interaction between two filaments was pronounced, leading to a co-motion of the filaments and enhanced elastic energy. This interaction decreased as the gap distance increased. Filaments in the 2STO mode exhibited significantly higher strain energy compared to the other modes. The elastic energy was concentrated at the rear part of the filaments and increased with higher gap distances and bending rigidities. Considering both energy harvesting efficiency and space utilization rate, a gap distance equal to 1 exhibited the best performance.

Dynamics of seaweed-inspired piezoelectric plates for energy harvesting from oscillatory cross flow

Inspired by the vibrations of aquatic plants such as seaweed in the unsteady flow fields generated by free-surface waves, we investigate a novel device based on piezoelectric plates to harvest energy from oscillatory cross flows. Towards this end, numerical studies are conducted using a flow-structure-electric interaction model to understand the underlying physical mechanisms involved in the dynamics and energy harvesting performance of one or a pair of piezoelectric plates in an oscillatory cross flow. In a single-plate configuration, both periodic and irregular responses have been observed depending on parameters such as normalized plate stiffness and Keulegan–Carpenter number. Large power harvesting is achieved with the excitation of natural modes. Besides, when the time scale of the motion and the intrinsic time scale of the circuit are close to each other the power extraction is enhanced. In a two-plate configuration with tandem formation, the hydrodynamic interaction between the two plates can induce irregularity in the response. In terms of energy harvesting, two counteracting mechanisms have been identified, shielding and energy recovery. The shielding effect reduces plate motion and energy harvesting, whereas with the energy recovery effect one plate is able to recovery energy from the wake of another for performance enhancement. The competition between these mechanisms leads to constructive or destructive interactions between the two plates. These results suggest that for better performance the system should be excited at its natural period, which should be close to the intrinsic time scale of the circuit. Moreover, using a pair of plates in a tandem formation can further improve the energy harvesting capacity when conditions for constructive interaction are satisfied.

Design and experimental investigation of a positive feedback magnetic-coupled piezoelectric energy harvester

A positive feedback magnetic-coupled piezoelectric energy harvester (PFM) is proposed to address the limitations of current piezoelectric energy collectors, including restricted acquisition direction, limited acquisition bandwidth, and low energy output. Firstly, the dynamic theoretical model of the energy harvester was established, and the optimization factors were explored, providing a solid theoretical foundation for subsequent research endeavors. The energy capture characteristics of rectangular beam and compound trapezoidal beam were compared through finite element simulation analysis. Subsequently, an experimental platform was constructed and an optimized experimental methodology was devised to analyze the energy capture characteristics and enhance the performance of the energy harvester. The results demonstrate that the positive feedback magnetic-coupled PFM with a trapezoidal beam exhibits superior energy capture efficiency. Furthermore, it is observed that the optimized energy harvester possesses wide frequency coverage, multi-directional capabilities, low-frequency adaptability, and facilitates easy vibration. When the 45 kΩ resistor is connected in series and subjected to a longitudinal external excitation amplitude of 0.5 g, it is capable of generating an average voltage and power output of 4.20 V and 0.39 mW respectively at a vibration frequency of 9 Hz. Similarly, when exposed to a transverse external excitation amplitude of 1 g, it can produce an average voltage output of 6.2 V and power output of 0.85 mW at a vibration frequency of 19 Hz. When the inclination angle of the energy harvester is set to 35 degrees, the maximum voltage output occurs at a frequency of 18 Hz and the Z-axis to X-axis force ratio of the energy harvester is 1.428. These research findings can serve as valuable references for piezoelectric energy harvesting applications in self-powered microelectronic systems.

Multi-piezoelectric energy harvesters array based on wind-induced vibration: Design, simulation, and experimental evaluation

The efficiency of a single piezoelectric energy harvester (PEH) is inadequate to meet the energy requirements of equipment, requiring the simultaneous operation of multiple PEHs. Consequently, this work conducts research on multi-piezoelectric energy harvesters (MPEH) array based on wind-induced vibration. Analyze the output characteristics of array configurations using simulation and experimental methods, including dual parallel array (PEH-2p), dual series array (PEH-2s), four-square array (PEH-4), and nine-square array (PEH-9) energy harvesters. The results indicate that the spacing ratio (L/D) is the primary factor influencing the output performance of the PEH array. Both of the starting and peak wind speeds of PEH-2p were below the reference value, but the power peak has increased. The starting wind speed of PEH-2s has been reduced, with a more significant improvement in the output performance of the downstream energy harvester compared to the upstream energy harvester. The output power of the downstream energy harvester has increased by 323.35 % in comparison to the reference value. Additionally, the PEH-4 demonstrates a boosting effect on the output power of both the upstream and downstream energy harvesters. The energy harvester in the center of the PEH-9 has the highest power peak, being 349.44 % higher than the reference value.

A viscoelastic nonlinear energy sink with an electromagnetic energy harvester: Narrow-band random response

Abstract Nonlinear energy sink is a passive energy absorption device that surpasses linear dampers, and has gained significant attention in various fields of vibration suppression. This is owing to its capacity to offer high vibration attenuation and robustness across a wide frequency spectrum. Energy harvester is a device employed to convert kinetic energy into usable electric energy. In this paper, we propose an electromagnetic energy harvester enhanced viscoelastic nonlinear energy sink (VNES) to achieve passive vibration suppression and energy harvesting simultaneously. A critical departure from prior studies is the investigation of the stochastic P-bifurcation of the electromechanically coupled VNES system under narrow-band random excitation. Initially, approximate analytical solutions are derived using a combination of a multiple-scale method and a perturbation approach. The substantial agreement between theoretical analysis solutions and numerical solutions obtained from Monte Carlo simulation underscores the method’s high degree of validity. Furthermore, the effects of system parameters on system responses are carefully examined. Additionally, we demonstrate that stochastic P-bifurcation can be induced by system parameters, which is further verified by the steady-state density functions of displacement. Lastly, we analyze the impacts of various parameters on the mean square current and the mean output power, which are crucial for selecting suitable parameters to enhance the energy harvesting performance.

Decision support system for community managed rainwater harvesting: A case study in the salinity-prone coastal region of Bangladesh

Climate change-induced saline intrusion into both surface and groundwater, extreme weather events, and unregulated water usage are serious threats to the drinking water supply in coastal areas worldwide, especially in least-developed countries. This research developed a data-driven decision-making methodology to evaluate the performance of rainwater harvesting (RWH) systems in the saline-prone southwestern coastal region of Bangladesh. Twenty-five community managed RWH systems, recently piloted in two major coastal districts, were considered the case study to develop and validate this evaluation tool. The evaluation methodology integrates daily water models, lifetime cost analysis, Geographic Information System (GIS)-based parameters supported by the Analytical Hierarchy Process (AHP), and field observation. While the meteorological parameters as well as the hydrological and economic performance were found to be highly suitable, 36 % of the systems showed moderate performance, as challenges remain in ensuring proper operation and maintenance practices at the community level. However, 40 % of the systems showed high performance, with two systems showing very high suitability, which suggests community managed RWH systems as a sustainable adaptation for coastal water supply.

Recyclable and mechanically tough nanocellulose reinforced natural rubber composite conductive elastomers for flexible multifunctional sensor

The development of flexible wearable multifunctional electronics has gained great attention in the field of human motion monitoring. However, developing mechanically tough, highly stretchable, and recyclable composite conductive materials for application in multifunctional sensors remained great challenges. In this work, a mechanically tough, highly stretchable, and recyclable composite conductive elastomer with the dynamic physical-chemical dual-crosslinking network was fabricated by the combination of multiple hydrogen bonds and dynamic ester bonds. To prepare the proposed composite elastomers, the polyaniline-modified carboxylate cellulose nanocrystals (C-CNC@PANI) were used as both conductive filler to yield high conductivity of 15.08 mS/m, and mechanical reinforcement to construct the dynamic dual-crosslinking network with epoxidized natural rubber latex to realize the high mechanical strength (8.65 MPa) and toughness (29.57 MJ/m3). Meanwhile, the construction of dynamic dual-crosslinking network endowed the elastomer with satisfactory recyclability. Based on these features, the composite conductive elastomers were used as strain sensors, and electrode material for assembling flexible and recyclable self-powered sensors for monitoring human motions. Importantly, the composite conductive elastomers maintained reliable sensing and energy harvesting performance even after multiple recycling process. This study provides a new strategy for the preparation of recyclable, mechanically tough composite conductive materials for wearable sensors.

An improved coupled tri-stable energy harvesting system with spring stops for passive control

Motivated by enhancing the DC power output of a tri-stable energy harvester (TEH), a passive control of a coupled TEH driven by colored noise is constructed by using spring stops. The cubic trilinear spring model is utilized to describe the piecewise nonlinear impact force introduced by the spring stops. Using the stochastic averaging technique based on energy-dependent frequency, the analytical expressions of joint probability density function (PDF) and harvested power are obtained. The effects of the impact distance, impact stiffness, and colored noise on stochastic dynamics and harvesting performance are further discussed. It is found that the spring stops can change the shape of the PDF to induce stochastic bifurcation phenomena. The TEH under passive control tends to oscillate among three potential wells to effectively improve the DC output. By adjusting the appropriate impact distance and stiffness, the harvesting performance can be optimized and improved. Moreover, the numerical simulations and experimental verifications well support the theoretical analysis. Based on the experimental results, the harvested power can be enhanced by choosing the appropriate material of the stop (i.e., the spring is the optimal one among three different materials).

Performance evaluation and optimal design for passive turbulence control-based hydrokinetic energy harvester using EWM-based TOPSIS

Passive turbulence control (PTC) in the form of square-shaped rods (SSR) is applied to improve the performance of the flow-induced vibration (FIV)-based energy harvester. The influence of SSR installation positions (θ) on the mechanical power and hydroelastic efficiency of SSR-cylinders is studied experimentally. Vortex-induced vibration (VIV) and VIV-galloping coupling modes are observed in this research. It is found that the SSR-cylinder with θ = 150° (VIV-galloping coupling) achieves the highest mechanical power, while the SSR-cylinder with θ = 180° (VIV) attains the highest hydroelastic efficiency. To evaluate the performance of energy harvesting and find the optimal design of the oscillator, the technique for order of preference by similarity to ideal solution (TOPSIS) is employed. The TOPSIS method considers both the average and maximum values of mechanical power and hydroelastic efficiency, with data-driven and adaptive weights estimated using the entropy weight method (EWM). It is indicated that the SSR installed at 150° obtains the optimal performance in a wide flow velocity range, followed by 140° and 70°. Finally, the effectiveness of the optimal design is validated by comparing it with other harvesters and the rationality of the proposed EWM-based TOPSIS method is analyzed in detail.