Search Results (191)

This study presents a pulley-buoy-accelerated linear wave power generation system and verifies its feasibility and effectiveness through experimental research. Compared with traditional wave power generation systems that rely on three-stage energy conversion, the proposed system eliminates intermediate energy transfer and conversion links, enabling direct extraction of electrical energy from wave-induced motion. Additionally, by incorporating a pulley assembly, the system amplifies the buoy’s motion speed. This enhancement boosts the power output of the linear generator and improves the system’s overall wave energy conversion efficiency. Under laboratory conditions, a small-scale prototype of the system and a swing-type wave generator were constructed. Experimental tests were conducted to examine how three key factors influence the system’s power generation performance: the number of stator coils, wave conditions (wave height and wavelength), and buoy size. The results indicate that three measures can effectively improve both the wave energy conversion efficiency and power generation performance of the pulley-buoy-accelerated system: increasing the number of stator coils, increasing wave height and wavelength, and moderately enlarging the buoy size. These findings offer valuable insights for the practical application and efficient operation of wave power generation systems. Full article

Wave energy is gaining momentum as a viable and environmentally sustainable source of renewable power, with the potential to contribute significantly to the global energy mix. Central to wave energy conversion is the power take-off system, where electromagnetic generators play a crucial role in determining overall system performance, reliability, and efficiency. This paper provides a review of wave energy conversion devices and classifies the main power take-off mechanisms. It evaluates and compares key generator types based on their performance under wave energy conditions. Among these, Permanent Magnet Synchronous Generators have demonstrated strong potential due to their high efficiency, power density, and suitability for low-speed direct drive configurations typical of wave environments. The review presents a detailed analysis of advanced permanent magnet generator topologies, focusing on structural designs, control methods, and wave-specific trade-offs. It also investigates hierarchical control strategies, where high-level decisions are based on wave conditions and low-level control ensures accurate generator operation. The paper aims to provide a broad perspective on the design and control of electromagnetic generators for wave energy systems. Full article

Modeling elementary diffusion processes in nanostructured materials is essential for developing platforms capable of interacting with high-speed physical signals. In this work, the photothermal response of a nano-hydroxyapatite/carbon nanotube (nHAp/CNT) composite was experimentally characterized and modeled through a cellular automaton (CA) framework designed to capture the thermal propagation of the hybrid system. Synthesizing nHAp/CNT composites enables the combination of the biocompatible and piezoelectric nature of nHAp with the enhanced photothermal response introduced by CNTs. UV–Vis reflectance measurements confirmed that CNT incorporation increases the optical absorption of the ceramic matrix, resulting in more efficient photothermal conversion. The composite was irradiated with a nanosecond pulsed laser, and the resulting thermal transients were compared with CA simulations based on a D2Q9 lattice configuration. The model accurately reproduces experiments, achieving R² > 0.991 and NRMSE below 2.4% for all tested laser powers. This strong correspondence validates the CA approach for predicting spatiotemporal heat diffusion in heterogeneous nanostructured composites. Furthermore, the model revealed a sensitive thermal coupling when two heat sources were considered, indicating synergistic enhancement of local temperature fields. These findings demonstrate both the effective integration of CNTs within the nHAp matrix and the capability of CA-based modeling to describe their photothermal behavior. Overall, this study establishes a computational–experimental basis for designing controlled thermal-wave propagation and guiding future multi-frequency or multi-source photothermal mixing experiments. Full article

This study proposes an improved variable-speed control strategy for Wells turbines in floating oscillating water column (OWC) wave energy converters (WECs) to address efficiency loss caused by turbine stalling. By optimizing the $\varphi$ from the conventional critical value from 0.3 to 0.11, the system achieves maximum mechanical power output while avoiding stall effects. A dynamic rotor-speed controller is designed to modulate turbine rotation behavior in response to real-time airflow velocity. This approach is validated using numerical simulations and MATLAB/Simulink R2021b models under both regular and irregular wave conditions. Results show a 124% increase in turbine power compared to uncontrolled operation, with stable DC-link voltage (+0.2%) and reduce torque ripple. The strategy enhances energy conversion efficiency by 51.2% and ensures safe operation under mechanical speed limits (3000 rpm), thus offering a practical solution for offshore WEC systems. Full article

As a critical component of marine renewable energy, wave energy has long remained a focal point in research on development and use. The Sharp Eagle wave energy converter (hereafter, Sharp Eagle WEC) exhibits wave energy capture efficiency-related advantages, which are attributed to the unique structural configuration of its Sharp Eagle wave-absorbing buoy (hereafter, buoy). Operational observations reveal that under severe sea conditions, buoy motion amplitude increases significantly. Consequently, the downstream hydraulic and power generation systems experience excessive power loads, and the converter exceeds displacement limits, causing collisions with end-stop structures, which compromises operational safety. Research findings indicate that the attitude of the buoy directly governs its motion characteristics. We proposed a ballast-and-load-based attitude control method for the buoy. This approach provides safe and efficient operation across all sea conditions. Via scaled model tests, converter operational data covering various ballast configurations were compared and analyzed, focusing on the effects of ballast on the capture width ratio (hereafter, CWR) and piston displacement range of energy conversion hydraulic cylinders. Herein, the feasibility of adjusting capture efficiency and motion displacement by controlling the buoy attitude is validated, providing a technical framework for efficient and safe operation of the WEC under all sea conditions. Full article

The ocean offers abundant wind and wave energy resources. This paper proposes an integrated concept that co-locates a semi-submersible floating wind platform with wave energy converters (WECs) to exploit the geographical consistency of these resources. By sharing the platform foundation and power transmission infrastructure, this integrated system enhances the utilization efficiency of marine space and renewable energy. Inspired by the principles of the Tuned Mass Damper (TMD) and leveraging mature hydraulic technologies from wave energy conversion and offshore drilling heave compensation systems, this study introduces a novel scheme. This scheme integrates a heave plate with a hydraulic Power Take-Off (PTO) system, functionally acting as a wave energy converter, to the floating platform. The primary objective is to mitigate the platform’s motion response while simultaneously generating electricity. The research investigates the motion performance improvement of this integrated platform under South China Sea conditions. The results demonstrate that the proposed WEC–PTO system not only improves the platform’s wave resistance and adaptability to deep-sea environments but also increases the overall efficiency of marine energy equipment deployment. Full article

This paper presents a broadband omnidirectional rectenna combined with a solar cell for hybrid energy harvesting, addressing the daytime-only limitation of solar cells via complementary RF energy harvesting. To avoid mutual interaction in integration, the solar cell is placed above the antenna to receive light/EM waves from different directions. A broadband discone antenna ensures omnidirectional RF reception from 1.56 to 6.63 GHz, while a single-stub matching circuit and voltage doubler enable rectifier operation from 1.4 to 3.6 GHz, with over 50% power conversion efficiency at 5 dBm. The measurement demonstrates that the hybrid system can yield 20.25 mW from combined RF/solar power. This broadband hybrid energy harvesting system shows potential for powering sensors throughout the day by integrating two complementary energy sources with minimal interaction. Full article

We present a single-slab metasurface that converts a normally incidental linearly polarized wave into either right- or left-handed circular polarization (RHCP/LHCP) through a simple ${90}^{\circ }$ mechanical rotation. Each unit cell comprises two L-shaped metallic resonators placed on the opposite faces of a low-permittivity substrate. Operating in transmission mode, the linear-to-circular (LTC) converter does not require any active electronic components. The geometry is optimized by using full-wave simulations to maximize the conversion up to 26% relative bandwidth with polarization conversion efficiency up to 65%, and insertion loss below 1.3 dB. Power balance analysis confirms low-loss, impedance-matched behavior. A scaled prototype fabricated from AWG-25 steel wires validates the model: experimental measurements closely reproduce the simulated bandwidth and demonstrate robust handedness switching. Because the resonance frequency depends primarily on resonator length and unit-cell pitch and thickness, the design can be retuned across the microwave spectrum through straightforward geometrical scaling. These results suggest that mechanical rotation could provide a simple and reliable alternative to electronic tuning in reconfigurable circular polarizers. Full article

The performance of wave energy converters (WECs) in terms of energy capture presents considerable challenges in enhancing conversion efficiency. This research proposes a structural design and operational principle for an omnidirectional oscillating buoy WEC (OOBWEC), featuring six absorbers arranged in a circular configuration. To validate the proposed design and operational principle, experimental investigations were conducted within a wave flume. The experimental findings indicate that the capture width ratio (CWR) peaked at approximately 68.15% when the incident wave period was 1.8 s and the wave height was 80 mm. It was observed that as the wave period increased, the CWR initially rose before gradually declining. Conversely, an increase in wave height corresponded with a gradual decrease in the CWR. Notably, due to the angle of the incoming waves, the power captured by the forward absorber significantly exceeded that of the other absorbers. These results provide a basis for future numerical simulations, and further experimental studies will be conducted to optimize the WEC’s structure and improve its energy conversion efficiency. Full article

An innovative multi-absorber 1 MW wave energy converter (WEC), Nankun, is proposed for efficient wave energy extraction. It comprises a semi-submersible floating platform, a wave energy capture mechanism, a hydraulic energy conversion system, and a mooring system. The WEC operates by converting fluctuating wave power into stable electrical output through a unique sharp eagle-shaped wave absorber coupled with a hydraulic energy conversion module. Scaled model experiments (1:25) demonstrated energy-capture efficiency ranges predominantly between 30% and 50% across 0.8–1.4 s wave periods, with a peak of 56.17%. Analysis of the wave direction effect revealed that the device achieved significantly a higher energy capture at 180 deg compared with 0 deg wave headings, with a relative efficiency ratio of approximately 1.0:0.6~0.8. A full-scale prototype with 10 absorbers was deployed in the South China Sea, achieving grid connection in November 2023. Operational data confirmed viability and generation capacity, with the peak daily output reaching 9850 kWh and a cumulative production of 89,852 kWh over 20 days. Full article

Ultrasonic guided wave interdigital transducers realized with piezoelectric materials are of interest for structural health monitoring systems because of their capability of performing Lamb wave mode selection with respect to single-element transducers. Besides this advantage, the coverage of large areas with a minimum number of elements is an important challenge and the problem of efficient excitation with integrated electronics must be solved. This work proposes an electrical matching network topology made of L and C passive components that can be designed for the trade-off between electrical to mechanical conversion efficiency and bandwidth. The network circuit is analyzed considering the equivalent transducer impedance and the output impedance of the driving electronics. The design rules derived by the transfer function analysis are described and a case study for a piezopolymer IDT is presented. Finally, with the implementation of the integrated matching network with the connector of the IDT, the effect of cable capacitance is minimized. In conclusion this article is a contribution to the study of using IDT efficiently and in a versatile mode for different electronic front-ends that usually operate at low power supply voltage. Full article

Wave energy is a highly concentrated energy resource with five times higher energy density than wind and at least ten times the power density of solar energy. It is expected to make a major contribution to addressing climate change and to help end our dependency on fossil fuels. Many ingenious wave energy conversion methods have been put forward, and a large number of wave energy converters (WECs) have been developed. However, to date, wave energy conversion technology is still in the demonstration application stage. Key issues such as survivability, reliability, and efficient conversion still need to be solved. The major hurdle is the fact that ocean waves provide a slow-moving, high-magnitude force, whereas most electric generators operate at high rotary speed and low torque. Coupling the slow-moving, high-magnitude force of ocean waves normally requires conversion to a high-speed, low-magnitude force as an intermediate step before a rotary generator is applied. This, in general, tends to severely limit the overall efficiency and reliability of the converter and drives the capital cost of the converter well above an acceptable commercial target. Magnetohydrodynamic (MHD) wave energy conversion makes use of MHD generators in which a conducting fluid passes through a very strong magnetic field to produce an electric current. In contrast to alternatives, the relatively slow speed at which the fluid traverses the magnetic field makes it possible to directly couple to ocean waves with a high-magnitude, slowly moving force. The MHD generator provides an excellent match to the mechanical impedance of an ocean wave, and therefore, an MHD WEC has no rotating mechanical parts with high speeds, no complex control process, and has good response to low sea states and high efficiency under all working conditions. This review introduces the system composition, working process, and technical features of WECs based on MHD generators first. Then, the research development, key points, and issues of wave energy conversion technology based on MHD generators are presented in detail. Finally, the problems to be solved and the future research directions of wave energy conversion based on MHD generators are pointed out. Full article

The conventional recycling of spent lithium-ion batteries (LIBs) is hindered by high energy consumption and severe environmental pollution. In this study, a novel method utilizing high-frequency electromagnetic radiation was proposed to process the black mass derived from spent NCM-LIBs, significantly reducing both energy consumption and chemical reagent usage. Conductive carbon black was introduced as an electromagnetic-wave-absorbing additive to improve the electromagnetic energy into thermal energy conversion efficiency during electromagnetic radiation. As a result, the decomposition and reduction of NCM materials can be completed within just 10 min at a microwave power of 500 W. Following electromagnetic irradiation, lithium was efficiently extracted via simple water leaching, achieving an extraction efficiency of 88.24%. Furthermore, a microwave heating device based on traveling-wave propagation was developed. Unlike conventional small-scale microwave systems that employ resonant cavities, this design enables improved heating uniformity, higher efficiency, and greater scalability for industrial microwave-assisted chemical processes. Full article

A hybrid wave energy conversion (WEC) system, integrating a backward bent duct buoy (BBDB) with an oscillating buoy (OB) via a flexible mooring chain, is introduced in this study. Unlike existing hybrid WECs, the proposed system dispenses with rigid mechanical linkages and enables flexible offshore deployment. Flared BBDB and buoy models with spherical, cylindrical, and semi-capsule shapes are designed and tested experimentally in a wave flume using both regular and irregular wave conditions. The effects of nozzle ratio (NR), coupling distance, buoy draft, and buoy geometry are systematically examined to investigate the hydrodynamic performance and energy conversion characteristics. It is found that NR at 110 under unidirectional airflow produces an optimal balance between pressure response, free surface displacement, and energy conversion efficiency. Energy extraction is significantly influenced by the coupling distance, with the hybrid system achieving maximum performance at a specific normalized spacing. The semi-capsule buoy improves power extraction ability and expands effective bandwidth due to asymmetric shape and coupled motion. These findings provide valuable insights into the coupling mechanism and geometric optimization for hybrid WECs. Full article

With the development of wave energy, a promising renewable resource, oscillating water column (OWC) devices, has been extensively studied for its potential in harnessing this energy. However, traditional OWC devices face challenges such as corrosion and damage from prolonged exposure to harsh marine environments, limiting their long-term viability and efficiency. To address these limitations, this paper proposes a novel U-tube type dual chamber OWC wave energy conversion device integrated within a marine vehicle. The research involves the design of a U-tube dual-chamber OWC device, which utilizes the pitch motion of a marine vehicle to drive the oscillation of water columns within the U-tube, generating reciprocating airflow that drives an air turbine. Numerical simulations using computational fluid dynamics (CFD) were conducted to analyze the effects of various structural dimensions, including device length, width, air chamber height, U-tube channel width, and bottom channel height, on the aerodynamic power output. The simulations considered real sea conditions, focusing on low-frequency waves prevalent in China’s sea areas. Simulation results reveal that increasing the device’s length and width substantially boosts aerodynamic power, while air chamber height and U-tube channel width have minor effects. These findings provide valuable insights into the optimal design of U-tube dual-chamber OWC devices for efficient wave energy conversion, laying the foundation for future physical prototype development and experimental validation. Full article