Large-scale Energy Harvesting Research Articles

Development of an Ocean Wave Energy Harvester using an Array of Flexible Piezoelectric Sensors

The ocean offers vast opportunities for unprecedented energy harvesting where most studies had concentrated on large scale energy harvesting from the ocean waves. However, there were minimal studies on low-scale energy harvesting. This study focuses on ambient, low-scale energy harvesting which theoretically can be used to power low energy consumption electrical appliances. The inherent characteristic of piezoelectric materials which can convert mechanical energy to electrical energy has created an alternative to generate energy from renewable sources including ocean waves. Initially, this study started with preliminary work which consisted of the development and testing of a lab scale piezoelectric energy harvester (PEH-1) which was tested along the beach area of Kuala Nerus, east coast of Malaysia. Results from PEH-1 had shown that the high tide produced more power level compared to low tide experiments. The findings from the first phase of this study served as a foundation study towards the development of an upscaled version of the PEH-1 in relation of mechanical and electronics, which was termed as PEH-2. Testing for PEH-2 was conducted in the coastal area of Pulau Bidong Laut, Kuala Nerus. Results from the second part of the study had shown that approximately almost 80% of the power harvested correlated linearly with wind speed, however after reaching 0.7W the peak dips down which was probably due to the instability of PEH-2 to be used in harsh open seas environment. This study had shown the feasibility of utilizing piezoelectric material to harvest low-scale power, however, several in-house modifications needed to be made for it to be fully functionable.

Stencil-Printed Scalable Radial Thermoelectric Device Using Sustainable Manufacturing Methods

In this study, we used n-chitosan-Bi2Te2.7Se0.3 and p-chitosan-Bi0.5Sb1.5Te3 composite inks to print a circular thermoelectric generator (TEG) device using a low-energy-input curing method. Thermoelectric (TE) composite films were fabricated using varying sizes of thermoelectric particles and a small chitosan binder (0.05 wt. %). The particles and binder were hot pressed at an applied pressure of 200 MPa and cured at 200 °C for 30 min. We achieved ZT of 0.35 for the n-type and 0.7 for the p-type TE composite films measured at room temperature. A radial TEG was fabricated using the best-performing n-type and p-type composite inks and achieved a power output of 87 µW and a power density of 727 µW/cm2 at a temperature difference of 35 K; these are among the best-reported values for printed TEG devices. Using a low-energy-input fabrication method, we eliminated the need for high-temperature and long-duration curing processes to fabricate printing devices. Thus, we envisage that the low-energy-input curing process and cost-effective printable strategy presented in this work pave the way for sustainable manufacturing of large-scale energy harvesting TEG devices.

A droplet-based multi-position and multi-layered triboelectric nanogenerator for large-scale raindrop energy harvesting

The triboelectric nanogenerator (TENG) is an emerging technology proven to have great potential in rainwater energy harvesting. However, most studies have focused only on single-position droplets, and there needs to be more research on multi-position, large-scale rainwater energy. In this work, we develop a multi-position and multi-layered triboelectric nanogenerator (MM-TENG) for large-scale raindrop energy harvesting. The multi-position structure can harvest multiple droplets in the horizontal direction. The water reservoir with multiple holes can convert a large amount of water into droplets, ensuring the output performance of the TENG. The multi-layered structure improves the efficiency of space utilization, as demonstrated by the current integration calculation, where a double-layered structure increases the output by 15.27% and a three-layered structure increases the output by 38.2% at the same height. Finally, we successfully lit up 50 LEDs and drove a commercial calculator with the power generated by the MM-TENG. This work provides a practical guide for collecting large-scale raindrop energy and self-driven sensing of the rainwater environment.

A Noncontact Constant-Voltage Triboelectric Nanogenerator via Charge Excitation

Triboelectric nanogenerators (TENGs) have attracted great attention in the distributed power sources field due to their ability to convert environment mechanical energy into electrical energy. However, the power density, durability, and humidity resistance of TENGs remain to be improved for large-scale application. Here, a noncontact constant-voltage triboelectric nanogenerator via charge excitation (ECV-TENG) is proposed to enhance the output performance, which first applies an adaptive-contact constant-voltage TENG as a charge pump and generates constant-voltage output via an elaborate noncontact phase-shift design. The ECV-TENG achieves an average power of 12.74 W m–3 Hz–2 and exhibits a long service life of over 2,000,000 cycles. Moreover, thanks to the humidity resistance of the constant-voltage pump and noncontact TENG, the ECV-TENG demonstrates a good humidity resistance at humidity up to 90%. This work not only promotes the potential applications of TENGs as a distributed energy supply but also provides new insights toward large-scale energy harvesting by TENGs.

Highly Flexible Triboelectric Nanogenerator Using Porous Carbon Nanotube Composites.

The rapid development of portable and wearable electronic devices has led researchers to actively study triboelectric nanogenerators (TENGs) that can provide self-powering capabilities. In this study, we propose a highly flexible and stretchable sponge-type TENG, named flexible conductive sponge triboelectric nanogenerator (FCS-TENG), which consists of a porous structure manufactured by inserting carbon nanotubes (CNTs) into silicon rubber using sugar particles. Nanocomposite fabrication processes, such as template-directed CVD and ice freeze casting methods for fabricating porous structures, are very complex and costly. However, the nanocomposite manufacturing process of flexible conductive sponge triboelectric nanogenerators is simple and inexpensive. In the tribo-negative CNT/silicone rubber nanocomposite, the CNTs act as electrodes, increasing the contact area between the two triboelectric materials, increasing the charge density, and improving charge transfer between the two phases. Measurements of the performance of flexible conductive sponge triboelectric nanogenerators using an oscilloscope and a linear motor, under a driving force of 2-7 N, show that it generates an output voltage of up to 1120 V and a current of 25.6 µA. In addition, by using different weight percentages of carbon nanotubes (CNTs), it is shown that the output power increases with the weight percentage of carbon nanotubes (CNTs). The flexible conductive sponge triboelectric nanogenerator not only exhibits good performance and mechanical robustness but can also be directly used in light-emitting diodes connected in series. Furthermore, its output remains extremely stable even after 1000 bending cycles in an ambient environment. In sum, the results demonstrate that flexible conductive sponge triboelectric nanogenerators can effectively power small electronics and contribute to large-scale energy harvesting.

Spherical Magnetoelastic Generator for Multidirectional Vibration Energy Harvesting.

Vibration is a common, usually wasted energy, and an attractive target for sustainable electricity generation. In this work, we introduce a new working mechanism to the vibration energy harvesting community by contributing a spherical magnetoelastic generator (S-MEG), which permits multidirectional vibration and is highly adaptable to many natural oscillation frequencies, exhibiting a resonant frequency of 24 Hz and a relatively wide working bandwidth of 15 Hz in the low-frequency range. It also features a low internal impedance of 70 Ω, which can respectively deliver a maximum short-circuit current density of 7.962 A·m-2 and a power density of 15.1 mW·m-2. To demonstrate the capability of S-MEG for ambient vibration energy harvesting, a 220 μF commercial capacitor was successfully charged to 2 V within 25 s, sustainably driving wearable bioelectronics for multiple physiological information monitoring. It could also harvest multidirectional vibration energy from both hand-shaking and bicycle-riding, generating approximately 2.5 mA and 6 mA alternating current from the motions, respectively, even with heavy perspiration or on a rainy day without the need for encapsulation. In summary, this work brings forth an appealing platform technology to the community of vibration energy harvesting, holding a collection of compelling features, including high current density, low inner impedance, intrinsic waterproofness, and scalability for large-scale vibration energy harvesting.

Defect engineering treatment of indium tin oxide significantly enhances the thermoelectric properties of cement-based composites for large-scale energy harvesting

When this cement-based composite with thermoelectric effect is used in roofs or sidewalks, it can capture heat energy through temperature difference and convert it into electrical energy while achieving cooling effect. We propose for the first time the use of indium tin oxide (ITO) powder with very stable thermoelectric properties, which is incorporated into the cement matrix together with expanded graphite (EG) to impart good thermoelectric properties for large-scale energy harvesting. The addition of ITO makes the conductive network of the cement-based composite more complete and increases the electrical conductivity by 1.43 times. The ITO powder was treated with a defect engineering approach to modulate its oxygen vacancy content and significantly increase the carrier concentration, which further brought about a simultaneous increase in the Seebeck coefficient and electrical conductivity, resulting in a 1.60-fold increase in the figure of merit (ZT) value to 1.49 × 10 −5 at 313 K.

Multilayered Helical Spherical Triboelectric Nanogenerator with Charge Shuttling for Water Wave Energy Harvesting.

As an important part of natural resources, islands support the marine economy and build a blue barrier for marine ecological civilization. However, the power supply on these islands is difficult, limiting the development of marine internet of things (IoTs). In order to break the status quo, this work applies triboelectric nanogenerators (TENGs) to island power supply and ecological monitoring. A spherical TENG with two multilayered helical units is designed to harvest water wave energy, in which the space utilization rate reaches 92.5%. Then a charge shuttling mechanism is developed to improve the electrical output. The output current and power of a single TENG without power management reach 200.3µA and 16.2mW respectively, corresponding to a peak power density of 23.2W m-3 . Moreover, a scheme of the power managed TENG is proposed for realizing large-scale wave energy harvesting. The TENG is demonstrated to successfully power a water quality detector, a Bluetooth thermo-hygrometer, and an intelligent wireless alarm system for remote environmental monitoring. This work not only proposes a new type of TENG for water wave energy harvesting with improved performance, but also provides a new strategy for intelligent ocean IoTs, which even contributes to the carbon neutralization.

Toward Large-Scale Energy Harvesting by a UV-Curable Organic-Coating-Based Triboelectric Nanogenerator.

Triboelectric nanogenerators (TENGs) stand out as an attractive form of technology for the efficient harvest of mechanical energy and the powering of wearable devices due to their light weight, simplicity, high power density, and efficient vibration energy scavenging capabilities. However, the requirement for micro/nanostructures and/or complex and expensive instruments hinders their cheap mass production, thus limiting their practical applications. By using a simple, cost-effective, fast spray-coating process, we develop high-performance UV-curable triboelectric coatings for large-scale energy harvesting. The effect of different formulations and coating compositions on the triboelectric output is investigated to design triboelectric coatings with high output performance. The TENG based on a hybrid coating exhibits high output performance of 54.5 μA current, 1228.9 V voltage, 163.6 nC transferred charge and 3.51 mW output power. Moreover, the hybrid coatings show good long-term output stability. All the results indicate that the designed triboelectric coatings show great potential for large-scale energy harvesting with the advantages of cost-effectiveness, fast fabrication, easy mass production and long-term stability.

0.5m Triboelectric Nanogenerator for Efficient Blue Energy Harvesting of All-Sea Areas.

Triboelectric nanogenerators (TENGs) to harvest ocean wave blue energy is flourishing, yet the research horizon has been limited to centimeter-level TENG. Here, for the first time, a TENG shell is advanced for ocean energy harvesting to 0.5m and an excellent frictional areal density of 1.03cm-1 and economies of scale are obtained. The unique structure of the multi-arch shape is adopted to untie the difficulty of fully getting the extensive friction layer contact. An inside steel plate is vertically placed in the center of every TENG block, which can activate the TENG to achieve complete contact even at a tilt angle of 7degrees. The proposed half-meter TENG (HM-TENG) has a broad response band from 0.1 to 2Hz, a total transferred charge quantity up to 67.2µC, and one single TENG can deliver an open-circuit voltage of 368V. Coupled with the self-stabilizing and susceptible features the ellipsoid shell brings, the HM-TENG can readily accommodate itself to the all-weather, all-sea wave energy harvesting. Muchmore, the HM-TENG is also applied to RF signal transmitters. This work takes the first step toward near-meter-scale enclosures and provides a new direction for large-scale wave energy harvesting.

Excellent thermoelectric properties of P-type cement-based composites through a universal defect engineering approach for large-scale energy harvesting

• A new method of preparing cement-based composites by changing the defect content. • The atmosphere treatment is applicable to a wide range of P-type metal oxides. • The combination of metal oxides and EG is a future trend with stable properties. When thermoelectric cement-based composites are used in roads and buildings, they effectively mitigate the urban heat island effect by absorbing heat from the environment and converting it into electricity, while reducing the surface temperature. Achieving large-scale applications requires cement-based composites with good thermoelectric properties. There have been many research efforts to obtain good thermoelectric properties, but the uncertainty of the enhancement effect is largely influenced by the researchers' process. The lack of a universal method to significantly improve the thermoelectric properties of cement-based composites has become a great obstacle for applications. In this paper, we obtained a universal approach by treating three P-type metal oxides Co 3 O 4 , CuO, and NiO in the oxidizing atmosphere. It was found that varying the defect content led to a significant improvement in the thermoelectric properties, obtaining excellent thermoelectric properties of P-type metal oxide cement-based composites, where the ZT values (measure of thermoelectric performance) increase by more than two times. This makes sense for stable large-scale energy harvesting in the future.

Nanoparticle-on-Mirror Metamaterials for Full-Spectrum Selective Solar Energy Harvesting.

Most broadband metamaterial absorbers are realized by patterning periodic arrays of plasmonic nanoparticles (>100 nm) on dielectric/metallic substrates to enable both electric and magnetic resonances. These metamaterials, however, require costly nanolithographic top-down techniques for fabrication. Here, we demonstrate new-concept nanoparticle-on-mirror (NoM) metamaterial absorbers by densely packing plasmonic nanoparticles of much smaller size (∼30 nm) on metal films directly. Such a simple but rational design enables the use of all-solution-based bottom-up processes. Because of the decoupling of electric and magnetic polarizations in these ultrasmall nanoparticles, excellent impedance match and near-perfect light absorption can be achieved in a broad band over the solar spectrum with weak thermal emission. Proof-of-concept large-area NoM metamaterial absorbers that offer a solar absorptance of 94% but a low IR emittance of 2% are experimentally demonstrated. The outstanding performance, bottom-up process, and great compatibility render the design promising for efficient and large-scale solar energy harvesting.

A droplet-based electricity generator for large-scale raindrop energy harvesting

Droplet-based electricity generator (DEG) has been demonstrated as efficient method to harvest energy from the natural environment. However, the complex structure and low output power density are still two barriers to wide applications. To this end, by making full use of the self-capacitance effect of the upper electrode, a droplet-based electricity generator with a simple open structure (SCE-DEG) was proposed in this paper. The working principle of SCE-DEG and the effects of electrode geometry and droplet parameters (volume, conductivity, and dropping frequency) on its output voltage were analyzed. Compared with the DEG, the upper electrode of SCE-DEG does not need to connect to the lower electrode and the ultra-high instantaneous peak output power (765 W/m2) can still be achieved by self-capacitance effect of the upper electrode. This research provides a reference for the large-scale raindrop energy harvesting.

Delay-optimal random access in large-scale energy harvesting IoT networks based on mean field game

With energy harvesting capability, the Internet of things (IoT) devices transmit data depending on their available energy, which leads to a more complicated coupling and brings new technical challenges to delay optimization. In this paper, we study the delay-optimal random access (RA) in large-scale energy harvesting IoT networks. We model a two-dimensional Markov decision process (MDP) to address the coupling between the data and energy queues, and adopt the mean field game (MFG) theory to reveal the coupling among the devices by utilizing the large-scale property. Specifically, to obtain the optimal access strategy for each device, we derive the Hamilton-Jacobi-Bellman (HJB) equation which requires the statistical information of other devices. Moreover, to model the evolution of the states distribution in the system, we derive the Fokker-Planck-Kolmogorov (FPK) equation based on the access strategy of devices. By solving the two coupled equations, we obtain the delay-optimal random access solution in an iterative manner with Lax-Friedrichs method. Finally, the simulation results show that the proposed scheme achieves significant performance gain compared with the conventional schemes.

Boosting the Power Output of a Cement-Based Triboelectric Nanogenerator by Enhancing Dielectric Polarization with Highly Dispersed Carbon Black Nanoparticles toward Large-Scale Energy Harvesting from Human Footsteps

Boosting the Power Output of a Cement-Based Triboelectric Nanogenerator by Enhancing Dielectric Polarization with Highly Dispersed Carbon Black Nanoparticles toward Large-Scale Energy Harvesting from Human Footsteps

A hybrid microwave sintered PZT composite as a flexible piezoelectric nanogenerator.

Interest in piezoelectric nanogenerators has grown extensively due to high piezoelectric coefficients. Piezoelectric ceramic-based devices have dominated research in large-scale energy harvesting. Morphotropic phase boundary PbZr0.52Ti0.48O3 (MPB-PZT) synthesized using Hybrid Microwave Sintering (HMS) at a low temperature (940 °C) for 20 min has emerged as a dense ceramic. The Rietveld refinement studies confirm its dual phase (tetragonal (P4mm) and rhombohedral (R3m)). The PZT ceramic is exploited as a piezoelectric material, which can improve the output piezoelectric potential of a piezoelectric nanogenerator (PENG). Multi-walled carbon nanotubes (MWCNTs) are evenly distributed in the PZT composite to reduce the internal resistance of the PENG. According to the percolation theory, small amounts of MWCNTs dispersed within the composite ink can significantly improve the output voltage of the PENG by acting as conductive bridges between the polymer (polyvinylpyrrolidone (PVP)) and ceramic particles. The concentration of PZT and the amount of MWCNTs are changed to enhance the device's output voltage. As a result, an optimized PENG with a PZT (1.5 g)/MWCNT (0.06 wt%)/PVP (4 g) (PVP - polyvinylpyrrolidone) composite film is obtained. The PENGs are mechanically poled. The optimised output voltage of the PENG is 16 Vpp, which could light up a series of 20 commercial light emitting diodes (LEDs). The PENG is attached to footwear and is noticed to efficiently harvest energy from daily human activities which demonstrate its practical applications.

Evolving from a hydrocarbon-based to a sustainable economy: Starting with a case study for Iran

Environmental and socioeconomic challenges facing many hydrocarbon-rich nations could help them evolve from hydrocarbon-based (black) into renewables-based (green) economies. In this paper, we present a case study for application of this Black Into Green (BIG) method for Iran. We show that with international cooperation Iran could indefinitely meet its energy and freshwater needs by leveraging large-scale renewable energy harvesting systems integrated with seawater pumped storage hydropower, reverse osmosis desalination, and enhanced distribution systems. This BIG transition could be facilitated by allocating a significant portion of Iran’s potential hydrocarbon-based income to acquire, develop, and deploy renewable energy technology that utilizes Iran’s immense solar and wind energy potential. Our analysis shows that developing just 1% of identified sites would provide over 30 TWh of annual renewable electricity generation and storage, and 221 million m3/day of renewably-powered desalination capacity to meet the freshwater needs of over 85% of its population. In addition to providing renewable energy design and manufacturing technology, the international community could also work with Iran to help evolve its nuclear power program toward small modular reactors for baseload power generation. Such an arrangement would contribute to regional and global security, and greatly reduce the Middle East’s carbon emissions of which Iran is the largest emitter. Results from this holistic approach could then serve as a model for the world economy to work with other resource-rich nations to reduce their environmental impact while modernizing their economies and helping them achieve the socioeconomic goals outlined in the UN’s Brundtland report.

Improving performance of triboelectric nanogenerators by dielectric enhancement effect

<h2>Summary</h2> As an emerging energy-harvesting technology, enhancing the output performance of triboelectric nanogenerators (TENGs) is crucial for its practical application. Here, a dielectric enhancement effect is firstly proposed to improve the output performance of TENGs. It is found that the dielectric enhancement layer greatly elevates the triboelectrification effect, and the enhanced performance is verified by all types of TENGs. Thus, the output power of alternative current TENG (AC-TENG) and direct current TENG (DC-TENG) realizes 8.5-fold and 2.6-fold enhancement of normal devices, respectively. Besides this, the dielectric enhancement layer with leakage performance is proven to be necessary for DC-TENG to produce a continuous output. Our work provides a simple and universal strategy for elevating the performance of all types of TENGs, which is beneficial to the promotion of large-scale energy harvesting by TENGs.

Enhanced thermoelectric performance of low carbon cement-based composites by reduced graphene oxide

Cement-based composites with thermoelectric effect have broad application prospects in the fields of urban heat island effect mitigation, winter road snow melting and ice melting and energy harvesting. Although cement-based composites have made great strides in terms of thermoelectric properties, the high carbon content makes their mechanical properties low, this is the main obstacle to further improvement of thermoelectric performance. In this paper, we added reduced graphene oxide (RGO) to cement through a liquid-phase mixing process to make cement particles adhere to RGO flakes, which effectively reduced the degree of mutual agglomeration between the RGO and improves the dispersion effect of RGO in cement-based materials. When the RGO content is 5.0 wt%, it has higher electrical conductivity (2.01 S/cm) compared with the RGO cement-based composite prepared by the ball milling process, achieve the ZTmax value of 0.23 × 10−4, and have good temperature stability with the highest output power of 8.27 × 10−3 mW/m2. This facilitates large-scale energy harvesting using thermoelectric cement-based composites.

Active resonance triboelectric nanogenerator for harvesting omnidirectional water-wave energy

<h2>Summary</h2> Water-wave energy, as one of the important renewable energies, is greatly difficult to efficiently harvest due to its characteristics of low frequency and randomly moving direction. Herein, we report an active resonance triboelectric nanogenerator (AR-TENG) system fabricated by using simple pendulum, tumbler, and flexible ring TENG, which can harvest omnidirectional and frequency varying water-wave energy through excellent structural design and resonance effect. Besides, thanks to the high-frequency damped motion of simple pendulum and tumbler, the high-frequency output generated by the AR-TENG system under the driving condition of low-frequency water wave can greatly improve the efficiency of wave energy harvesting. More importantly, based on the low damping coefficient, resonance effect, and elimination of water screening effect, the output performance of AR-TENG system in the water wave is closest to the simulated test. This work not only can realize the omnidirectional water-wave energy harvesting by TENG but also provide a method for large-scale blue energy harvesting.