Efficient Energy Harvesting Research Articles

Nanostructured Cu12+xSb4S13 tetrahedrites prepared by solvothermal synthesis in 1-(2-aminoethyl)piperazine for efficient thermal energy harvesting

Intrinsically low lattice thermal conductivity and the earth-abundant nature of elements make tetrahedrites very promising sulfur-based materials for thermoelectric applications. Although the thermoelectric performance of lightweight sulfides is usually restricted due to high lattice thermal conductivity, nanoengineering may effectively enhance the energy conversion performance of tetrahedrites by disturbing phonon transport. In this work, we modified our unique solvothermal synthesis method with 1-(2-aminoethyl)piperazine as a solvent and pure elements as reagents to obtain both copper-rich and copper-poor tetrahedrites with nanometric grain sizes ranging from 40 to 300 nm. The powders obtained were densified by the PECS method at T = 573 K and p = 40 MPa. The structural and thermal properties of the fabricated materials were systematically investigated as a function of temperature to revisit the phase evolution of the Cu-Sb-S system in the vicinity of the tetrahedrite compounds. The Seebeck coefficient of the investigated materials changes from 150 µVK−1 up to 400 µVK−1 at 300 K due to the effective tuning of the carrier concentration. In turn, the nanocrystalline nature of the prepared tetrahedrites, which influences the strong phonon scattering at grain boundaries, results in an ultralow lattice thermal conductivity of around 0.25 Wm−1K−1 at 300 K. As a result of the tuned electronic transport and ultralow lattice thermal conductivity, the highest ZT parameter of 0.9 at 596 K was achieved for the nominal composition Cu13Sb4S13. This is one of the best values reported to date for low-cost and environmentally friendly tetrahedrites at this temperature. The resultant nanomaterials can be used as components in novel inorganic and organic-inorganic composites for direct conversion of heat to electricity.

Triboelectric-electromagnetic hybrid nanogenerator for harvesting blue energy and creating an ocean wave warning system.

The abundant water wave energy on Earth stands as one of the most promising renewable blue energy sources, as it exhibits minimal dependence on weather, time and temperature. However, the low fluctuation frequency and extremely irregular nature of the wave energy restrict both the methods and efficiency of energy harvesting. In this study, a packed box-like hybrid nanogenerator was designed, comprising two single-electrode triboelectric nanogenerators (TENGs) and two electromagnetic generators (EMGs). The outputs of both the TENG and EMG were demonstrated under different fluctuation frequencies and swing amplitudes, inspiring the development of a wave warning system. The maximum output voltage, current, and transferred charge of the single TENG, as part of hybrid nanogenerator (HG), reach approximately 110 V, 2.3 μA, and 50 nC, respectively. Its peak power reaches 85.3 μW under a resistance load of 20 MΩ at a frequency of 2 Hz. The EMG component produced maximum output voltages and currents of up to 0.45 V and 1.2 mA, respectively. The peak power is approximately 95.6 μW with a resistance load of 200 Ω. The output performances of the TENG and EMG increase linearly with the increase in the swing angle. Most importantly, a packed box-like hybrid nanogenerator can be conveniently packaged for harvesting energy from water waves. A wave energy collection array floating on the sea is proposed for harvesting blue energy and creating a self-powered ocean wave warning system.

Deciphering the anisotropic energy harvesting responses of an above room temperature molecular ferroelectric copper(II) complex single crystal.

The mechanical/piezoelectric and/or thermal/pyroelectric energy harvesting efficiency is observed to be extremely good in multi-component ferroelectric inorganic oxides in their single-crystal form rather than in their polycrystalline counterparts (pellets and thick/thin films). However, growing such multi-component single crystals is a challenging and cost-intensive process besides the difficulty in tuning their long-range ferroic ordering and the involvement of toxic heavy elements. Instead, discrete inorganic metal complexes can be potential alternatives for which one can overcome these caveats by an appropriate design strategy. Herein, we report a biocompatible and an above room temperature (Tc > 380 K) molecular ferroelectric [Cu2(L-phe)2(bpy)2(H2O)](ClO4)2·2H2O single crystal (1) with profound anisotropic piezo- and pyro-electric responses along different unit cell axes. Energy harvesting data at room temperature reveal that the highest possibility of scavenging mechanical energy (∼30 μW m-2) is preferentially along the b-axis. This is attributed to the large spontaneous polarization (Ps = 2.5 μC cm-2) and piezoelectric coefficient (d33 = 23.5 pm V-1) observed along the b-axis, compared to those along the other two axes. The highest output voltage (7.4 V cm-2) and pyroelectric coefficient (29 μC m-2 K-1) obtained for the single-crystal device are impressively higher than those of most of the reported materials. Such a molecular anisotropic single-crystal piezo-/pyro-electric nanogenerator (SC-PENG) with excellent mechanical and thermal energy harvesting competence is reported for the first time.

Development of low-cost micro-fabrication procedures for planar micro-thermoelectric generators based on thin-film technology for energy harvesting applications.

With the rapid proliferation of portable and wearable electronics, energy autonomy through efficient energy harvesting has become paramount. Thermoelectric generators (TEGs) stand out as promising candidates due to their silent operation, high reliability, and maintenance-free nature. This paper presents the design, fabrication, and analysis of a micro-scale TEG for powering such devices. A planar configuration was employed for its inherent miniaturization advantages. Finite element analysis using ANSYS reveals that a double-layer device under a 50 K temperature gradient generates an impressive open-circuit voltage of 1417 mV and a power output of 2.4 μW, significantly exceeding its single-layer counterpart (226 mV, 0.12 μW). Validation against the analytical model results yields errors within 2.44% and 2.03% for voltage and power, respectively. Furthermore, a single-layer prototype fabricated using paper shadow masks and sputtering deposition exhibits a voltage of 131 mV for a 50 K temperature difference, thus confirming the feasibility of the proposed design. This work establishes a foundation for developing highly efficient micro-TEGs for powering next-generation portable and wearable electronics.

Energy Harvesting from Waste Heat using Thermoelectric Generators

This research examines the synergistic benefits and impact of Thermoelectric Generators (TEGs) in energy harvesting, emphasizing their contribution to improving system efficiency via appropriate integration with energy management systems. The empirical findings indicate a significant 15% enhancement in energy conversion efficiency via enhanced waste heat recovery using TEGs, coupled with an 8% augmentation in total system performance attributable to sophisticated energy management strategies. Furthermore, there is a notable 10% decrease in energy losses, achieved by meticulous management of temperature gradients and regulation of power output. Total Energy Efficiency Metrics indicate a 12.5% enhancement in energy usage, a 2% decrease in system downtime attributable to the improved dependability of TEG units, and a 4°C reduction in average operating temperature, hence assuring increased lifespan of the devices. These findings underscore the practical advantages of integrating TEGs into waste heat recovery systems, enhancing the ongoing discussion on sustainable energy solutions by offering definitive proof of their effectiveness and the collaborative effect they exert on energy harvesting and system efficiency.

Investigation of enhanced geothermal system in the Basal Cambrian Sandstone Unit, Alberta, Canada

Given the climate challenge, society is seeking low greenhouse gas emission energy sources. In jurisdictions such as Alberta, Canada where power is largely generated through the combustion of natural gas, geothermal offers a compelling option but it remains unclear as to its economic and technical viability. Here, we examine the potential for an enhanced geothermal system in the Basal Cambrian Sandstone Unit in Alberta, Canada. Prior to geothermal operation, hydraulic fracturing is conducted to enhance the permeability of the thermal reservoir. This lowers the pressure drop required for circulating fluids through the system. The results show that the open-loop enhanced geothermal system realizes an energy produced to energy invested ratio from 4 to 9 depending on different operating rate. The results also suggest that applying hydraulic fracturing can accelerate energy harvesting and energy efficiency over the early stages of the process but the greater the injection rate, the smaller is this benefit of hydraulic fracturing stimulation.

Efficient Resource Management, Energy Harvesting and Power Consumption in IOT

Internet of Things (IoT) devices are becoming more and more common in today's society, with applications found in a wide range of fields. These gadgets, which come with sensors and communication capabilities, collect and send enormous amounts of data from the real world to digital networks. The need for internet infrastructure has increased significantly due to the exponential expansion in data generation brought about by the proliferation of IoT devices. Energy harvesting in Internet of Things devices can maximize their application, positioning, and functionality, resulting in the ideal synergy. Additionally, because IoT devices do not have direct access to a power source, their power consumption is frequently supplied by a battery. This is frequently brought on by being situated in areas where it is just not feasible to reach the electrical grid. Thus, the research is concentrated on creating strategies to enhance the energy efficiency of Internet of Things devices, look into energy harvesting methods, optimize resource allocation and management, and discover ways to lower power consumption.

Improvement in hot carrier dynamics of all-inorganic halide perovskite CsPbI3 on doping Cu

Hot carrier extraction is crucial for efficient solar energy harvesting, and lead halide perovskite nanocrystals (NCs) are potential candidates for photovoltaic and light-emitting applications. Therefore, swift extraction of hot carriers is an immediate requirement to improve the energy conversion efficiency, which need longer thermalization time. To address this issue, we synthesized nominally Cu-doped CsPbI3 NCs with enhanced structural and optical characteristics compared to undoped CsPbI3 NCs. We investigated the hot carrier dynamics in both the NCs at different fluences using ultrafast transient absorption spectroscopy. Interestingly, we observed very fast thermalization at higher fluences that indicated breaking of the phonon bottleneck. On the contrary, doped NCs preserved the effects and decayed over a longer period of time possibly due to increase in size and introduction of shallow trap states of Cu 3d and Cu 4s electrons in the conduction band, as computed using density functional theory. Notably, as the carrier–carrier interaction increased, we observed a dominating bandgap renormalization in the doped system compared to the undoped system. Overall, our studies improve the understanding of Cu doping in enhancing the hot carrier dynamics in perovskites and open possibilities for further investigation in the quantum phenomenon of these materials.

A mechanically robust spiral fiber with ionic-electronic coupling for multimodal energy harvesting.

Wearable electronics are some of the most promising technologies with the potential to transform many aspects of human life such as smart healthcare and intelligent communication. The design of self-powered fabrics with the ability to efficiently harvest energy from the ambient environment would not only be beneficial for their integration with textiles, but would also reduce the environmental impact of wearable technologies by eliminating their need for disposable batteries. Herein, inspired by classical Archimedean spirals, we report a metastructured fiber fabricated by scrolling followed by cold drawing of a bilayer thin film of an MXene and a solid polymer electrolyte. The obtained composite fibers with a typical spiral metastructure (SMFs) exhibit high efficiency for dispersing external stress, resulting in simultaneously high specific mechanical strength and toughness. Furthermore, the alternating layers of the MXene and polymer electrolyte form a unique, tandem ionic-electronic coupling device, enabling SMFs to generate electricity from diverse environmental parameters, such as mechanical vibrations, moisture gradients, and temperature differences. This work presents a design rule for assembling planar architectures into robust fibrous metastructures, and introduces the concept of ionic-electronic coupling fibers for efficient multimodal energy harvesting, which have great potential in the field of self-powered wearable electronics.

Structurally and surficially activated TiO2 nanomaterials for photochemical reactions.

Renewable fuels and environmental remediation are of paramount importance in today's world due to escalating concerns about climate change, pollution, and the finite nature of fossil fuels. Transitioning to sustainable energy sources and addressing environmental pollution has become an urgent necessity. Photocatalysis, particularly harnessing solar energy to drive chemical reactions for environmental remediation and clean fuel production, holds significant promise among emerging technologies. As a benchmark semiconductor in photocatalysis, TiO2 photocatalyst offers an excellent solution for environmental remediation and serves as a key tool in energy conversion and chemical synthesis. Despite its status as the default photocatalyst, TiO2 suffers from drawbacks such as a high recombination rate of charge carriers, low electrical conductivity, and limited absorption in the visible light spectrum. This review provides an in-depth exploration of the fundamental principles of photocatalytic reactions and presents recent advancements in the development of TiO2 photocatalysts. It specifically focuses on strategic approaches aimed at enhancing the performance of TiO2 photocatalysts, including improving visible light absorption for efficient solar energy harvesting, enhancing charge separation and transportation efficiency, and ensuring stability for robust photocatalysis. Additionally, the review delves into the application of photodegradation and photocatalysis, particularly in critical processes such as water splitting, carbon dioxide reduction, nitrogen fixation, hydrogen peroxide generation, and alcohol oxidation. It also highlights the novel use of TiO2 in plastic polymerization and degradation, showcasing its potential for converting plastic waste into valuable chemicals and fuels, thereby offering sustainable waste management solutions. By addressing these essential areas, the review offers valuable insights into the potential of TiO2 photocatalysis for addressing pressing environmental and energy challenges. Furthermore, the review encompasses the application of TiO2 photochromic systems, expanding its scope to include other innovative research and applications. Finally, it addresses the underlying challenges and provides perspectives on the future development of TiO2 photocatalysts. Through addressing these issues and implementing innovative strategies, TiO2 photocatalysis can continue to evolve and play a pivotal role in sustainable energy and environmental applications.

An octave box inspired energy regularization triboelectric nanogenerator for highly efficient wave energy harvesting

Inspired by the mechanical transmission structure of octave boxes, this work proposes a novel energy regularization triboelectric nanogenerator to effectively convert chaotic wave energy into stable electric output.

Negative space charge modulated ion transport through PEDOT:PSS hydrogels integrating nanofluidic channels for highly efficient osmotic energy harvesting

The exploitation of ion-selective membranes with high power density and low resistance is crucial for harvesting osmotic energy in natural environments.

Numerical Simulation on VIV Energy Harvesting of Four Cylinders in Close Staggered Formation with Different Mass Ratios

Nowadays, the demand for marine renewable and clean energy from fluid flow in the oil and gas industry has made electricity the most sought-after and indispensable source of uncontrollable power worldwide. Vortex-Induced Vibrations (VIV) energy harvesting is a promising technology in harnessing energy from flowing water bodies. This study focuses on numerically investigating the VIV of rigid circular cylinders as a sustainable energy source, utilizing a Vortex-Induced Vibration Aquatic Clean Energy (VIVACE) converter to harvest energy from the ocean. Specifically, the research explores the vibration behavior of closely arranged cylinders with different mass ratios, both at low and high values. The study aims to understand the effects of mass ratios on the VIV converter’s performance with four cylinders in close staggered formation. The power conversion of the VIV energy converter model with varying mass ratios (ranging from 2.36 to 12.96) is thoroughly examined, with simulations conducted at a Reynolds number of 82000. The results demonstrate that the maximum converted power peaks at 7.48 W for a mass ratio of 2.36, whereas a higher mass ratio of 12.96 only yields 4.33 W. This emphasizes the significant impact of lower mass ratios in enhancing the power generation from VIV. Overall, the findings of this research provide essential insights to optimize the layout of VIVACE converters in a close staggered array, facilitating the efficient harvesting of energy from flowing water bodies for sustainable and clean energy resources.

Enhancing Power Generation in Triboelectric Nanogenerators via Integration of Graphene Nanoplatelets and Polyvinyl Alcohol

Triboelectric nanogenerators (TENGs) provide promising power supply solutions by transforming mechanical energy into electrical energy. However, enhancing electrical performance of TENGs is essential for their widespread practical applications and commercialization. In this study, we fabricated TENGs in vertical contact‐separation mode using a tribopositive material—polyvinyl alcohol (PVA) slime—which is biocompatible, flexible, and wearable, decorated with graphene nanoplatelets (GnPs), and paired with tribonegative silicone. We analyzed the correlation between the electrical performance of the TENGs and the inherent triboelectric properties of the constituent material, including the evaluation of surface roughness, the measurement of the contact potential difference (CPD), and the material’s dielectric constant. The incorporation of GnPs increased the dielectric constant of the composite material and its electron‐donating tendency, thus, increasing the contact potential difference. The GnPs concentration of 1 wt% was identified as the optimal value, resulting in a 42% increase in power density. The 1 wt% GnPs@PVA&Silicone TENG exhibited an open‐circuit voltage of 718 V and a peak power density of 15.3 W/m2. This study sheds light on enhancing the energy harvesting efficiency of TENGs through the utilization of biocompatible tribopositive and tribonegative materials.

Structural optimization of laminated leaf-like piezoelectric wind energy harvesters based on topological method

In this paper, a series of leaf-like piezoelectric elements are proposed by using laminated structure of polypropylene (PP) and Polyvinylidene fluoride (PVDF) film to collect wind energy through vortex induced vibration. Topology optimization based on solid isotropic material with penalization method is employed in seeking optimal configurations of the elements. The PP and PVDF layer were set as optimization variables respectively to obtain topological layouts that would be equivalent to maximizes the overall strain energy as the objective function. Four simple shapes of piezoelectric elements with different topological configurations are manufactured and tested in wind tunnel to estimate the energy harvesting capabilities. The experimental results show that the reinforcement optimized long trapezoid model has the highest open-circuit output voltage of 4.01 V and output power of 6.125 μW at the wind speed of 12 m/s. For the optimization of piezoelectric materials, the short trapezoid model can reach the open circuit output voltage of 2.061 V and output power of 1.158 μW. It indicated that the topology optimization can indeed improve the energy harvesting efficiency of the piezoelectric element. However, this method is not universal at present, which means that the external shape of the model will influence the performance of the relevant optimization results.

Bioinspired gradient-structured wood interfaces achieving efficient ion diffusion to generate electricity from natural evaporation

A bioinspired gradient-structured wood-based interfacial evaporative nanogenerator, that overcomes the slow ion diffusion that limits efficient energy harvesting.

Fluorine-free coating-based droplet triboelectric nanogenerators for highly efficient energy harvesting

A new structural droplet-based (D)-TENG is designed with a communal electrode (CE) based on a silicon resin-modified acrylic resin coating for efficiently harvesting water droplet energy and reducing costs.

Improving Photovoltaic System Performance with Artificial Neural Network Control

Photovoltaic systems play a pivotal role in renewable energy initiatives. To enhance the efficiency of solar panels amid changing environmental conditions, effective Maximum Power Point Tracking (MPPT) is essential. This study introduces an innovative control approach based on an Artificial Neural Network (ANN) controller tailored for photovoltaic systems. The aim is to elevate the precision and adaptability of MPPT, thereby improving solar energy harvesting. This research integrated an ANN controller into a photovoltaic system in order dynamically optimize the operating point of solar panels in response to environmental changes. The performance of the ANN controller was compared with traditional MPPT approaches using simulation in Simulink/Matlab. The results of the simulation showed that the ANN controller performed better than the traditional MPPT techniques, highlighting the effectiveness of this method for dynamically changing solar panel performance. The ANN particularly demonstrates higher precision and adaptability when environmental conditions vary. The strategy consistently achieves and maintains the maximum power point, enhancing overall energy harvesting efficiency. The integration of an ANN controller marks a significant advance in solar energy control. The study highlights the superiority of the ANN controller through rigorous simulations, demonstrating increased accuracy and adaptability. This approach not only proves effective, but also has the potential to outperform other MPPT strategies in terms of stability and responsiveness.

Stochastic performance of a torsional-flutter harvester in non-stationary, turbulent thunderstorm outflows

Efficiency of a torsional-flutter energy harvester in thunderstorm-like wind flows is studied. The apparatus has been proposed in recent years as an alternative to other flapping windmills of medium size due to its simple installation and operational mechanism. The paper investigates a rapid change of wind load intensity, induced by a thunderstorm, which may either reduce the output energy conversion or damage the apparatus. Aeroelastic load is replicated through unsteady Wagner’s indicial theory. The study explores the influence of both slowly-varying wind velocity variations, non-stationary turbulence of variable intensity and load perturbations. A stochastic model is derived to investigate both pre-critical and post-critical regimes. Various configurations are considered.

Hand-held rolling magnetic-spring energy harvester: Design, analysis, and experimental verification

Aiming at the random and low-frequency characteristics of human motion, a hand-held rolling magnetic-spring energy harvester is proposed to scavenge energy from handshaking. The harvester applies the rolling movement of a magnetically suspended magnet and possesses the merit of low damping. The dynamic model is established and the open-circuit voltages are predicted by combining Faraday's law of electromagnetic induction and finite element analysis. By calculating magnetic flux through coils, the effect of the coil’s position on energy harvesting efficiency is studied through numerical and experimental approaches. Experimental results under harmonic excitations indicate that the coil positioned directly below the stable equilibrium position of the moving magnet has the best output capability, and a maximum open-circuit voltage of 1.33 V and a half-power bandwidth of 1.61 Hz is achieved at 0.3 g. Under handshaking excitation, an instantaneous peak power of 20.15 mW is achieved, along with a maximum average power of 2.22 mW. The corresponding volume and mass power densities are respectively 26.04 μW/cm3 and 23.28 μW/g. Furthermore, handshaking excitation in 5 s to charge a capacitor of 470 μF could enable the watch, time display, timer, and hygrothermograph to operate for 1100 s, 513 s, 86 s, and 35 s respectively, demonstrating the brilliant application foreground of the proposed harvester.