Harvest Energy Research Articles

Reconfigurable MIMO-based self-powered battery-less light communication system

Simultaneous lightwave information and power transfer (SLIPT), co-existing with optical wireless communication, holds an enormous potential to provide continuous charging to remote Internet of Things (IoT) devices while ensuring connectivity. Combining SLIPT with an omnidirectional receiver, we can leverage a higher power budget while maintaining a stable connection, a major challenge for optical wireless communication systems. Here, we design a multiplexed SLIPT-based system comprising an array of photodetectors (PDs) arranged in a 3 × 3 configuration. The system enables decoding information from multiple light beams while simultaneously harvesting energy. The PDs can swiftly switch between photoconductive and photovoltaic modes to maximize information transfer rates and provide on-demand energy harvesting. Additionally, we investigated the ability to decode information and harvest energy with a particular quadrant set of PDs from the array, allowing beam tracking and spatial diversity. The design was explored in a smaller version for higher data rates and a bigger one for higher power harvesting. We report a self-powering device that can achieve a gross data rate of 25.7 Mbps from a single-input single-output (SISO) and an 85.2 Mbps net data rate in a multiple-input multiple-output (MIMO) configuration. Under a standard AMT1.5 illumination, the device can harvest up to 87.33 mW, around twice the power needed to maintain the entire system. Our work paves the way for deploying autonomous IoT devices in harsh environments and their potential use in space applications.

Storage capacity plan and transition of heterogeneous energy at regional strategic level: A financial derivative perspective

Energy storage plays a key role in harvesting energy among heterogeneous energy sources. To transform heterogeneous energy and plan storage capacity at the regional strategic level, this study simulates storage capacity settings for heterogeneous energy in a certain region (Jiangsu Province in China) from the perspective of investment portfolio. This study then implements adjustments between the generation side and storage side during operations under a hedging ideology. Lastly, this study uses thermal energy on the generation side as an example to apply the switching real option method in decision-making for transitioning from thermal energy to renewable energy during disposal. The conclusion indicates that, from a financial derivative perspective, planning of heterogeneous energy storage capacity proves to be more efficient than existing regional plans and decision-making for transformation achieves investment triggers with higher energy values. Thus, this study aids the power system in planning energy storage and managing heterogeneous energy more economically and comprehensively at the regional strategic level.

Analysis and Application of Poly(vinyl alcohol) (PVA) and Polyacrylonitrile (PAN) Nanofiber Membrane-Based Triboelectric Nanogenerators.

The triboelectric property of materials is used to harvest energy from intentional or nonintentional sources of vibration. Contact mode freestanding dielectric based nanogenerators (CFTENGs) have many advantages when compared with other modes of triboelectric nanogenerators. The property of dielectric materials plays an important role in the energy harvesting process. In this work, we aim to fabricate nanofiber membranes of poly(vinyl alcohol) (PVA) and polyacrylonitrile (PAN) and study their properties for CFTENGs. The morphology and porosity of both membranes were tested experimentally. The mechanical property is modeled with a representative volume element (RVE) technique to understand its deflection behavior. In addition, an electromechanical model is developed to predict and analyze the behavior of those membranes in the energy conversion process. Our research reveals that the PAN dielectric layer achieves a maximum open circuit voltage of 192 kV compared to the PVA dielectric layer (2.2 kV) in the CFTENG system. In comparison, the dielectric layer of the PAN nanofiber membrane reflects its flexibility to generate electrical energy in a CFTENG with the effect of contact electrification and electrostatic induction under various sources of unused energies for a wide range of applications. Moreover, the same methodology is applied to various sources of vibration, and their performance is reported. With an appropriate power management circuit, we can design a PAN membrane-based TENG for various applications.

Damping efficiency of the fractional Duffing system and an assessment of its solution accuracy

Dynamical systems with high damping efficiency in a wide frequency band can be useful on a small scale – for harvesting energy from ambient vibrations, and on a large scale – for damping harmful vibrations of mechanical structures. In this paper we present an assessment of the quality of solutions and damping efficiency of systems with fractional order derivatives. To simulate the fractional system the fourth-order Runge–Kutta method and Grünwald–Letnikov methods are used. We propose a coefficient for assessing the quality of solutions to fractional systems by reference to the quality of the calculated energy balance. As an exemplary system we study the Duffing model with embedded additional fractional-order derivative terms. Based on this coefficient, intervals of key numerical simulation parameters are determined to ensure the appropriate quality for the calculations of energy flows and energy balance. The determined values of these parameters are then used in tests of the damping efficiency of the studied system. Our results show that by modifying the fractional terms it is possible to configure a system that exhibits a “broadband effect”, i.e. a system that is characterized by high-amplitude vibrations and, consequently, high energy efficiency in a wide range of excitation frequencies.

A tunable pendulum-like piezoelectric energy harvester for multidirectional vibration

Harvesting energy from vibrations using piezoelectric mechanism has attracted much attention for powering wireless sensors over the past decade. This paper proposes a tunable pendulum-like piezoelectric energy harvester for multidirectional vibration (TP-PVEH) to enhance the power generation characteristic, durability, and environmental adaptability of energy harvester. Unlike traditional cantilevered piezoelectric vibration energy harvesters (PVEHs), which typically lowered working frequencies by adding the weight of proof mass at the end of beam or reshaping beam, TP-PVEH employed a pendulum to harness low-frequency vibrations. Moreover, in contrast to typical pendulum-like PVEHs, the pendulum in this design was not mounted at the end of beam but was attached to a radial spherical plain bearing (RSPB) structure, which avoided the irreversible beam damage caused by gravitational force. TP-PVEH utilized simple-pendulum-induced RSPB motion to smoothly pluck piezoelectric beams, subjecting the piezoelectric beams to unidirectional compressive stress only. Meanwhile, the RSPB structure's capability to facilitate multidirectional rotation enabled TP-PVEH to efficiently capture energy from various directions. Theoretical analysis, numerical analysis and experiment tests were conducted to validate the design and examine how excitation and structural parameters influenced on the output performance of TP-PVEH. The results demonstrated that the excitation amplitude, excitation angle, proof mass, and mass distance brought significant effects on the output characteristic of TP-PVEH. The working frequency, output voltage and power could be efficiently tuned by the abovementioned parameters. With an excitation amplitude of 3 mm, TP-PVEH achieved an optimal output power of 9.81 mW and an output power density of 11.37 μW/mm3, operating with a load resistance of 200 kΩ at a frequency of 12.5 Hz.TP-PVEH could power 100 blue LEDs and a calculator. Additionally, the ability of TP-PVEH to charge capacitors further demonstrated its practical power supply capabilities.

Admittance-based equivalent circuit modeling of multi-patch piezoelectric energy harvesting plate

Abstract Harvesting energy from mechanical vibration using piezoelectric material is a common method to power small electronics and batteries. Implementation of multiple piezo-patches to plate-like structures increases the power capacity and frequency bandwidth of the energy harvester since multiple patches can capture more vibrational modes of the dense plate dynamics. To optimize the harvested electrical output using advanced harvesting circuits, equivalent circuit modeling (ECM) is a useful technique for representing the entire electromechanical system in circuit- simulator-software (LTspice). The ECM technique based on finite-element (FE) simulation has been used for plate-like structures with only one single-piezo-patch-harvester in the literature. However, when multiple patches are integrated into a plate-like structure, their coupling can cause charge cancelation, resulting in complex dynamics that cannot be handled by the existing ECM methods. This paper presents three new methodologies for extracting a multi-mode ECM of the harvesters (e.g.: multi-patch piezo-harvesters integrated into a plate), using an admittance-based system identification approach utilizing FE results. The first method incorporates the ECM of multi-patch harvester into a single ECM, so called OGC. It includes a circuit branch where multiple patches have only one ECM branch for each vibration mode, which requires less equivalent circuit elements and hence less computational cost. The second and third so-called respective ground uncoupled (RGU) and respective ground coupled (RGC) ECM methods generate circuit branches for each piezo-patch and for each vibration mode, whereby their electrical connection (e.g. parallel or series) is later configured in LTspice. The RGU method provides a general multi-patch modeling approach while RGC method provides ECM parameters for each patch simultaneously when they are all connected which is the case in network harvester analysis. The ECMs of parallel multi-patch harvesters are validated by system-level FE simulations. The proposed admittance-based ECM methods are reliable for deriving the system parameters of multi-patch harvesters.

High-output solid[sbnd]liquid triboelectric nanogenerator enhanced by the regulation of interfacial wettability

Triboelectric nanogenerators (TENGs), as a new strategy for harvesting energy from nature, have attracted widespread attention in the field of water droplet energy capture. As a friction layer material, the solidliquid electrification phenomenon of coatings has been studied. However, little attention is paid to the influence of the surface wettability of the coating itself on the electrical signal of the droplet generator. In this study, alkyl/phenyl pure silicone resin was utilized as a substitute for fluorine-containing polymer materials. This substitution not only mitigated the risk of environmental pollution from TENG friction materials but also resulted in varying wettability of the silicone resin coating through plasma and surface structure treatment. The droplet-based Double-electrode (D-TENG) and Single-electrode (S-TENG) coating-based triboelectric nanogenerators were fabricated. Through the integration of a high-speed camera and ammeter, the motion state of water droplets on surfaces with different wettability closely correlates with their charged behavior. This correlation is utilized to observe the motion state of water droplets on hydrophilic-hydrophobic surfaces in four stages: contact, spreading, contraction, and sliding. Under the double-electrode structure, as the water contact angle of the coating increased from 6.84° to 139.77°, the short-circuit current initially increased and then decreased, peaking at 466 µA when the contact angle was 98.48°, representing a 677-fold increase from the initial 0.689 µA. In the single electrode structure, the short-circuit current increased from 2.66 nA to 700 nA, indicating a 263-fold increase. Studying the varied wettability of the surface of silicone resin coating aids in comprehending the application of the coating material in solid-liquid friction electrification for energy collection. Furthermore, it offers insight into selecting appropriate coating materials for friction coatings in future applications.

Elastomeric Ionic Hydrogel-Based Flexible Moisture-Electric Generator for Next-Generation Wearable Electronics.

Rapid consumption of traditional energy resources creates utmost research interest in developing self-sufficient electrical devices to progress next-generation electronics to a level up. To address the global energy crisis, moisture-electric generators (MEGs) are proving to be an emerging technology in this field, capable of powering wearable electronics by harvesting energy from abundantly available ambient moisture without any requirement for external/additional energy. Recent advances in MEGs generally utilize an inorganic, metal, or petroleum-based polymeric material as an active material, which may produce sufficient current but lacks the flexibility and stretchability required for wearable electronics. Herein, we prepared an elastomer-based ionic hydrogel as an active material, and an MEG was fabricated by placing the ionic hydrogel on a PET sheet with two copper tapes on both sides of the hydrogel. The preparation of the hydrogel was thoroughly optimized and characterized in terms of spectroscopic analysis, swelling, water retention, and mechanical and rheological studies. The highly stretchable (350%) fabricated MEG is capable of producing a short-circuit current (JSC) of 16.1 μA/cm2, an open-circuit voltage (VOC) of 0.24 V, and a power density of 3.86 μW/cm2. The synergistic effect of the ion concentration gradient and the redox reaction on electrodes can be considered MEG's working principle. Apart from the current generation, this device is also used as a self-powered electronic sensor to monitor different physical activities by measuring breathing patterns. This prepared device is also capable of sensing the proximity of a hand. Therefore, our low-cost, easily fabricable, sustainable MEG device can be a potential aspirant for next-generation self-powered wearable electronics in healthcare applications.

Screw transmission structure based triboelectric–electromagnetic hybridized generator for efficiently harvesting energy from a single mechanical stimulation

Among various electromechanical conversion technologies, the triboelectric-electromagnetic hybrid generator (TEHG) stands out with its capacity to operate across a wider frequency range. Nevertheless, extracting more electricity from a single mechanical stimulation remains a significant challenge. In this work, we propose a screw transmission structure based TEHG (ST-TEHG) that converts the contact-separation motion into continuous rotation. This transformation enables the device to produce multiple pulse outputs in both compression and rebound processes. Specifically, the threaded barrel is designed to rotate continuously under the action of the pressing lever. Excess energy is stored as elastic potential energy in the tower spring, which then initiates the threaded barrel’s reverse rotation upon the release of external force. Through systematical optimization of the screw transmission structure and device’s performances, ST-TEHG achieves an energy utilization efficiency that is 70.86 times than the device with conventional contact-separation mode in an operating cycle. The developed ST-TEHG demonstrates promising applications in smart factories for indoor conditions monitoring, such as temperature and humidity, assembly line monitoring, and hazardous zones warning. This screw transmission structure sets a precedent for highly efficient mechanical energy harvesting, propelling the practical advancement of hybrid generators.

A Magneto-Electric Device for Fluid Pipelines with Vibration Damping and Vibration Energy Harvesting.

This study introduces an innovative energy harvesting system designed for industrial applications such as fluid pipelines, air conditioning ducts, sewer systems, and subsea oil pipelines. The system integrates magneto-electric flow coupling and utilizes a dynamic vibration absorber (DVA) to mitigate the vibrations induced by fluid flow while simultaneously harvesting energy through magnetic dipole-dipole interactions in a vibration energy harvester (VEH). The theoretical models, based on Hamilton's Principle and the Biot-Savart Law, were validated through comprehensive experiments. The results indicate the superior performance of the small-magnet system over the large-magnet system in both damping and power generation. The study analyzed the frequency response and energy conversion efficiency across different parameters, including the DVA mass, spring constant, and placement location. The experimental findings demonstrated significant vibration reduction and increased voltage output, validating the theoretical model. This research offers new avenues for energy harvesting systems in pipeline infrastructures, potentially enhancing energy efficiency and structural integrity.

A Comprehensive Review of Strategies toward Efficient Flexible Piezoelectric Polymer Composites Based on BaTiO3 for Next-Generation Energy Harvesting

The increasing need for wearable and portable electronics and the necessity to provide a continuous power supply to these electronics have shifted the focus of scientists toward harvesting energy from ambient sources. Harvesting energy from ambient sources, including solar, wind, and mechanical energies, is a solution to meet rising energy demands. Furthermore, adopting lightweight power source technologies is becoming more decisive in choosing renewable energy technologies to power novel electronic devices. In this regard, piezoelectric nanogenerators (PENGs) based on polymer composites that can convert discrete and low-frequency irregular mechanical energy from their surrounding environment into electricity have attracted keen attention and made considerable progress. This review highlights the latest advancements in this technology. First, the working mechanism of piezoelectricity and the different piezoelectric materials will be detailed. In particular, the focus will be on polymer composites filled with lead-free BaTiO3 piezoceramics to provide environmentally friendly technology. The next section will discuss the strategies adopted to enhance the performance of BaTiO3-based polymer composites. Finally, the potential applications of the developed PENGs will be presented, and the novel trends in the direction of the improvement of PENGs will be detailed.

Recent Progress of Self-Powered Optoelectronic Devices Based on 2D Materials

Harvesting energy through light radiation is an attractive solution for powering wireless devices in the future. In particular, self-driven optoelectronic devices are especially attractive for low-energy devices on the Internet of Things. Two-dimensional (2D) materials at atomic scale thicknesses are very attractive for future self-powered optoelectronic devices due to not only their unique electronic and optical properties, but also the feasibility to fabricate desirable heterostructures, which differ from their bulk counterparts and conventional optoelectronic materials. In this review, we mainly summarized the mechanism and performance of self-powered optoelectronic devices based on 2D materials. The figure of merit and mechanism of self-driving optoelectronic devices including the interface-junction effect, bulk photovoltaic effect, and photothermoelectric effect are discussed in detail. In addition, the recent progress on the performance of self-powered optoelectronic devices based on 2D materials is compared, followed by the perspective of this field. This review is aimed to give a generalized knowledge of 2D self-powered optoelectronic devices, and thus prompt the exploration and development of novel functional devices based on 2D materials.

Potential Power Output from Vehicle Suspension Energy Harvesting Given Bumpy and Random-Surfaced Roads

The energy efficiency of vehicles is a crucial challenge relating to sustainable energy preservation and regeneration methods. Regenerative breaking has proven feasible, and there is interest in whether harvesting energy from a vehicle’s suspension is similarly feasible. We here provide methods for estimating the amount of power that can be regenerated from the suspension for given vehicle and road parameters. We show that a reasonable road model is a generalised Gaussian process known as AR(1). Using this model, we can derive the key equation used in the ISO 8608 standard for measuring road roughness, such that the AR(1) parameters can be related to the measured road roughness data. We find that the road roughness coefficient of ISO 8608 and the diffusion coefficient of the AR(1) road are equal up to a factor. We provide an analytical expression for the maximum amount of power that can be generated for given road and car parameters, derived via Fourier analysis. We further model harvesting from large bumps using Simulink. These results help to estimate the potential power output given the measured road data.

Advantages of a novel truncated cone DE-air generator in energy conversion

Abstract Harvesting energy from ambient environments such as vibrations is a feasible approach to selfpower low powered electric devices. T- he dielectric elastomer generator (DEG) is a type of novel electrostatic generator with superior vibration energy harvesting (EH) performance. On the basis of traditional DEGs, a new concept of dielectric elastomer (DE)-air generator (DEAG), which contains the air layer and the DE membrane (DEM) as a composite dielectric layer, is proposed in this paper for the first time. Inspired by a classical truncated cone DEG (TC-DEG) concept, the novel truncated cone DEAG (TC-DEAG) is designed and comprehensively studied. Compared with the TC-DEG, the proposed TC-DEAG provides the larger capacitance ratio, leading to superior electrical output. The energy conversion mechanisms of both the TC-DEG and the TC-DEAG under a regular linear reciprocating excitation are analyzed theoretically by deducing the deformation condition of the DEM and the electrical outputs. Through measuring the capacitance of the DEM under deformations and testing the output voltage of the fabricated generators, the proposed theoretical models and predictions are verified. Moreover, numerical simulations based on the verified theoretical model are conducted to reveal the influences of some important system parameters on the EH performances of both generators, providing guidelines for the performance improvement of the generators.

Carbon Superstructure‐Supported Half‐Metallic V2O3 Nanospheres for High‐Efficiency Photorechargeable Zinc Ion Batteries

AbstractPhotorechargeable zinc ion batteries (PZIBs), which can directly harvest and store solar energy, are promising technologies for the development of a renewable energy society. However, the incompatibility requirement between narrow band gap and wide coverage has raised severe challenges for high‐efficiency dual‐functional photocathodes. Herein, half‐metallic vanadium (III) oxide (V2O3) was first reported as a dual‐functional photocathode for PZIBs. Theoretical and experimental results revealed its unique photoelectrical and zinc ion storage properties for capturing and storing solar energy. To this end, a synergistic protective etching strategy was developed to construct carbon superstructure‐supported V2O3 nanospheres (V2O3@CSs). The half‐metallic characteristics of V2O3, combined with the three‐dimensional superstructure assembled by ultrathin carbon nanosheets, established rapid charge transfer networks and robust framework for efficient and stable solar‐energy storage. Consequently, the V2O3@CSs photocathode delivered record zinc ion storage properties, including a photo‐assisted discharge capacities of 463 mA ⋅ h ⋅ g−1 at 2.0 A ⋅ g−1 and long‐term cycling stability over 3000 cycles. Notably, the PZIBs assembled using V2O3@CSs photocathodes could be photorecharged without an external circuit, exhibiting a high photo conversion efficiency (0.354 %) and photorecharge voltage (1.0 V). This study offered a promising direction for the direct capture and storage of solar energy.

Carbon Superstructure-Supported Half-Metallic V2O3 Nanospheres for High-Efficiency Photorechargeable Zinc Ion Batteries.

Photorechargeable zinc ion batteries (PZIBs), which can directly harvest and store solar energy, are promising technologies for the development of a renewable energy society. However, the incompatibility requirement between narrow band gap and wide coverage has raised severe challenges for high-efficiency dual-functional photocathodes. Herein, half-metallic vanadium (III) oxide (V2O3) was first reported as a dual-functional photocathode for PZIBs. Theoretical and experimental results revealed its unique photoelectrical and zinc ion storage properties for capturing and storing solar energy. To this end, a synergistic protective etching strategy was developed to construct carbon superstructure-supported V2O3 nanospheres (V2O3@CSs). The half-metallic characteristics of V2O3, combined with the three-dimensional superstructure assembled by ultrathin carbon nanosheets, established rapid charge transfer networks and robust framework for efficient and stable solar-energy storage. Consequently, the V2O3@CSs photocathode delivered record zinc ion storage properties, including a photo-assisted discharge capacities of 463 mA ⋅ h ⋅ g-1 at 2.0 A ⋅ g-1 and long-term cycling stability over 3000 cycles. Notably, the PZIBs assembled using V2O3@CSs photocathodes could be photorecharged without an external circuit, exhibiting a high photo conversion efficiency (0.354 %) and photorecharge voltage (1.0 V). This study offered a promising direction for the direct capture and storage of solar energy.

Designing a Hybrid Energy-Efficient Harvesting System for Head- or Wrist-Worn Healthcare Wearable Devices.

Battery power is crucial for wearable devices as it ensures continuous operation, which is critical for real-time health monitoring and emergency alerts. One solution for long-lasting monitoring is energy harvesting systems. Ensuring a consistent energy supply from variable sources for reliable device performance is a major challenge. Additionally, integrating energy harvesting components without compromising the wearability, comfort, and esthetic design of healthcare devices presents a significant bottleneck. Here, we show that with a meticulous design using small and highly efficient photovoltaic (PV) panels, compact thermoelectric (TEG) modules, and two ultra-low-power BQ25504 DC-DC boost converters, the battery life can increase from 9.31 h to over 18 h. The parallel connection of boost converters at two points of the output allows both energy sources to individually achieve maximum power point tracking (MPPT) during battery charging. We found that under specific conditions such as facing the sun for more than two hours, the device became self-powered. Our results demonstrate the long-term and stable performance of the sensor node with an efficiency of 96%. Given the high-power density of solar cells outdoors, a combination of PV and TEG energy can harvest energy quickly and sufficiently from sunlight and body heat. The small form factor of the harvesting system and the environmental conditions of particular occupations such as the oil and gas industry make it suitable for health monitoring wearables worn on the head, face, or wrist region, targeting outdoor workers.

What Makes a Photobattery Light-Rechargeable?

The demand for autonomous off-grid devices has led to the development of "photobatteries", which integrate light-energy harvesting and electrochemical energy storage in the same architecture. Despite several photobattery chemistries and designs being reported recently, there have been few insights into the physical conditions necessary for charge transfer between the photoelectrode and counter electrode. Here, we use a three-electrode photobattery with a dye-sensitized TiO2 photoelectrode, triiodide (I-/I3 -) catholyte, and anodes with varying intercalation potentials to confirm that photocharging is only feasible when the conduction band quasi-Fermi level (EFc) is positioned above the anode intercalation/plating potential. We also show that parasitic reactions after the battery is fully charged can be accelerated if the voltage of the battery and solar cell are not matched. The integration of multiple anodes in the same photobattery ensures well-controlled measurement conditions, allowing us to demonstrate the physical conditions necessary for charge transfer in photobatteries, which has been a topic of controversy in the field.

Highly Efficient, Flexible, and Self-Healable Moisture-Driven Energy Harvester Based on 2D Vanadium Pentoxide Nanosheets

The ubiquitous source of atmospheric moisture brought about a fascinating research avenue of extracting atmospheric water to generate sustainable electricity. Energy may be extracted from ambient moisture with obvious and substantial advantages. This point-of-use technology provides a decentralized alternative to meet the energy needs in isolated off-grid places. Unlike traditional energy generators which predominantly rely upon fossil fuel, moisture-induced energy generators can extract energy from moisture in a sustainable and eco-friendly way. Herein, we demonstrated a self-healable moist electric generator (MEG) based on vanadium pentoxide (V2O5) 2D nanosheet membranes. Lamellar membranes of V2O5 nanosheets have been shown to be excellent cation conductors and excellent materials for harvesting energy from ambient moisture. Ultra-thin 2D nanosheets of V2O5 was obtained by treatment of bulk V2O5 crystals with hydrogen peroxide. V2O5 nanosheet membrane was fabricated by vacuum-assisted filtration of 2D V2O5 nanosheets dispersion over a PTFE support membrane. The V2O5 membrane was easily peeled off from the support membrane on drying to obtain a flexible and freestanding V2O5 membrane. The V2O5 membrane consisting of percolated nanofluidic channels was sandwiched between a bottom solid copper foil and a perforated copper foil as the bottom electrode. The top electrode is perforated for exposure to atmospheric humidity. As the atmospheric water molecules come in contact with the V2O5 surface, an open-circuit voltage of 0.5 Volts and a short-circuit current of 0.3 microamperes is generated. The generated voltage and current is attributed to the preferential flow of cations through the V2O5 nanochannels. The exposed surface and edges of V2O5 nanosheets have a high negative surface charge which results in the splitting of water molecules into H3O+ and OH- ions. An electrical double layer (EDL) is established at the V2O5/water interface which selectively permits H3O+ ions through the channels. The mobile ions of the EDL transport through the nanofluidic channels creating a gradient between the two electrodes, resulting in a constant potential difference between the top and bottom electrodes which is harvested as electric current. The MEGs can be easily connected in parallel or series to enhance the current and voltage respectively. We demonstrate ten MEGs connected in series to power small electronic devices such as calculators and humidity meters. One of the key features of the V2O5 MEG is its ability to repair any physical damage to the active material owing to the water-assisted healing characteristics V2O5 membrane. Figure 1

Energy harvesting from carbon-based rope driven by capillary flow

Harvesting energy from the natural environment has garnered significant interest due to its eco-friendliness and spontaneity. Here, we present a novel carbon-based rope hydrovoltaic generator, fabricated by a straightforward dip-coating method. Water infiltrates the rope and flows driven by capillary forces, creating a wet/dry interface. An electrical double layer (EDL) forms at the carbon-water interface where wetting occurs, causing protons to accumulate between the wet and dry regions and establishing a substantial potential difference. Under environmental conditions, this setup can induce an open circuit voltage of approximately 0.4 V when a 0.01 mL droplet is applied to the carbon-based rope (with a resistance of 1 MΩ). As a proof of concept, the output performance can be scaled through series and parallel connections, successfully charging a 100 μF capacitor that powers a digital calculator. This simple and flexible hydrovoltaic device provides a new method for clean energy harvesting in practical applications.