Search Results (90)

Floating tidal platforms provide a flexible solution for offshore tidal–stream energy exploitation, but their wave-induced motions may affect platform stability, turbine operation and power performance. Integrating wave energy converters (WECs) with a floating tidal platform provides a potential approach to absorb wave energy and modify platform motions. However, the dynamic role of a WEC array attached to a floating tidal platform remains insufficiently understood, especially with respect to array layouts, power take-off (PTO)-induced coupling and absorbed power. This study investigates the effects of WEC array layout on the motion response and absorbed power of a catamaran-type floating tidal platform under irregular wave excitation. Three representative WEC array layouts, namely longitudinal, transverse and hybrid arrangements, were compared with a baseline platform without WECs. A coupled numerical model was established by combining frequency-domain radiation-diffraction analysis and time-domain simulations of mooring system and PTO dynamics based on ANSYS AQWA 2023R2. The hydrodynamic model was verified through code-to-code comparisons with OrcaWave 11.6, and the PTO power model was checked against published numerical results. The results show that the WEC array layout has a significant influence on both platform response and power absorption. Among the investigated layouts, the transverse array provides the most effective overall motion suppression, with average reductions of 36.83% in heave responses and 52.62% in pitch responses compared with the baseline platform. Frequency-domain results indicate that pure multi-body hydrodynamic interaction has a limited influence on the platform response amplitude operators (RAOs) and wave-excited forces, whereas time-domain results reveal much stronger layout-dependent responses once PTO coupling was included. The WECs’ absorbed power was strongly affected by the geometric relationship between the PTO rotation plane and the dominant platform motion plane. When these two planes were aligned in coplanarity, platform motion enhances the relative PTO rotation and increases output power. These findings indicate that, for floating tidal platforms with relatively small displacement, WEC arrays should be treated as distributed dynamic subsystems rather than only as energy-harvesting add-ons. The results can provide useful guidance for the layout design and coupled dynamic assessment of floating hybrid tidal–wave energy converters (HTWEC). Full article

A hybrid system combining wave energy converters (WECs) and a floating breakwater presents significant potential for developing commercial-scale wave power operations. The assessment of the hydrodynamic characteristics of a WEC array–floating breakwater system under irregular waves remains in the early stages and requires further investigation. Based on the linear potential theory, a time-domain numerical model is established to evaluate the performance of a hybrid WEC array–floating breakwater system in a target sea area. The interaction between the WECs and the floating breakwater is analyzed. Results show that for the hybrid system with a triangular-baffle-type WEC array under irregular waves, the annual average wave power is 1.16 MW and the annual energy production is 10.16 × 10³ MW·h, representing a 241.2% improvement compared with that of the isolated WEC array. The standard deviations of the mooring forces for the hybrid system with the triangular-baffle-type WEC array are reduced by 13.8% in the surge direction and 26.9% in the pitch direction, while increasing by 90.0% in the heave direction. Similar conclusions are obtained for the motion of the floating breakwater. The findings and data reported in this study provide guidance for the engineering application of a hybrid WEC array–floating breakwater system. Full article

This study examines the hydrodynamic performance and energy conversion mechanisms of a dual-float wave energy converter (WEC) to address the limitations of single-float WECs regarding energy capture efficiency and cost-effectiveness. A three-dimensional numerical wave tank is constructed utilizing computational fluid dynamics (CFDs) technology and STAR-CCM+ to simulate the dynamic response of the dual-float system under specific wave conditions characterized by a height of 0.1 m and a period of 1.5 s. The effects of a front-rear configuration with a quarter-wavelength spacing on the converter’s power output, turbofan rotational characteristics, and heave motion are systematically analyzed. The results indicate that the wave-facing float attains a consistent rotational speed of 4 rad/s, exhibiting significant fluctuations in heave displacement and velocity. Conversely, the downstream float exhibits diminished motion amplitude, a constant rotational velocity of 2.5 rad/s, and curtailed power generation attributable to wave diffraction and energy shielding from the wave-facing float. The mutual hydrodynamic interference between the floats influences the total energy conversion efficiency, as evidenced by the dual-float system’s array impact factor of 0.989. A parametric study covering multiple wave conditions and float spacing is supplemented to reveal the influence law of key parameters on system performance. This paper elucidates the fundamental mechanism of hydrodynamic coupling in dual-float arrays and offers a theoretical foundation and technical guidance for the optimal design and engineering application of arrayed WECs. Full article

This paper focuses on power grid integration of wave energy converter (WEC) arrays that minimize added energy storage for maximizing power capture as well as smoothing the oscillatory power inputs into the grid. In particular, a linear right circular cylinder WEC array that implements complex conjugate control is compared and contrasted to a nonlinear WEC array that implements an hourglass buoy shape while both are integrated into the grid utilizing phase control (i.e., relative spacing of the WEC array) on the input powers to the grid. The Hamiltonians of the two WEC systems are derived, enabling a direct comparison of real and reactive power, with reactive power reflecting the utilization of stored energy. The control systems are simulated in MATLAB/Simulink under both regular wave conditions and irregular seas generated from a Bretschneider spectrum. For the linear right circular cylinder buoy, the proportional-derivative complex conjugate controller requires an external energy storage device to supply reactive power, whereas the nonlinear hourglass buoy inherently provides reactive power through its geometric design. This study demonstrates that: (i) The unique geometry of the hourglass buoy reduces the required energy storage size for the nonlinear system while simultaneously increasing power output. (ii) Phase control of the hexagonal hourglass array further enhances real power capture. Together, these effects substantially decrease the size and demand on the individual buoys and grid integration energy storage requirements. Full article

This study assesses the feasibility and profitability of marine hybrid clusters, combining wave energy converters (WECs) and offshore wind turbines (OWTs) to power households and marine aquaculture. Researchers analyzed two coastal sites: La Serena, Chile, with high and consistent wave energy resources, and Ensenada, Mexico, with moderate and more variable wave power. Two WEC technologies, Wave Dragon (WD) and Pelamis (PEL), were evaluated alongside lithium-ion battery storage and green hydrogen production for surplus energy storage. Results show that La Serena’s high wave power (26.05 kW/m) requires less hybridization than Ensenada’s (13.88 kW/m). The WD device in La Serena achieved the highest energy production, while PEL arrays in Ensenada were more effective. The PEL-OWT cluster proved the most cost-effective in Ensenada, whereas the WD-OWT performed better in La Serena. Supplying electricity for seaweed aquaculture, particularly in La Serena, proves more profitable than for households. Ensenada’s clusters generate more surplus electricity, suitable for the electricity market or hydrogen conversion. This study emphasizes the importance of tailoring emerging WEC systems to local conditions, optimizing hybridization strategies, and integrating consolidated industries, such as aquaculture, to enhance both economic and environmental benefits. Full article

Because of its reliability, large reserves, and high safety standards, wave energy power generation has become an important part of the renewable energy industry. Hybrid-sized wave energy converter arrays consist of floats of different sizes. They have higher output power and stability and are the future development direction of wave power generation. However, the energy-absorbing floats in existing power calculation models are still in a traditional uniform-size configuration and cannot accurately calculate the energy generated by hybrid-sized wave energy converter arrays. In this paper, a time-domain power calculation model of hybrid-sized wave energy converter arrays is proposed. Based on linear wave theory, a frequency-domain hydrodynamic model is constructed and transformed into a time-domain model. The time-domain characteristics and influencing factors of wave energy converters are analyzed. Finally, a time-domain power calculation model of hybrid-sized wave energy converter arrays is established. Based on the irregular model setting and water entry conditions, an experimental verification study on the power calculation model is carried out using the wave energy converter previously developed by the research team. The results show that the average error of the power calculation model proposed in this paper is less than 10%, demonstrating the accuracy of the model. Full article

A novel Dual Bayesian optimization strategy is formed for an array of wave energy converters with adaptive resonance to maximize the annual performance through the energy conversion processes from irregular waves to electricity. A wave energy converter with adaptive resonance changes the natural frequency of power take-off dynamics for varying irregular waves, resulting in the maximum annual energy production. The first step of the two-step Dual Bayesian optimization determines the geometric layout of the array, which maximizes the first energy conversion to the total array excitation for irregular waves occurring annually. The second step optimizes the operational parameters of individual wave energy converters in the optimized array to maximize the power generation in varying sea states through simultaneous conversion to mechanical and electrical energy. The coupled hydrodynamics are solved in the frequency domain, and the power performance is evaluated by solving the Cummins’ equation in the time domain extended for multiple floating bodies, each strongly coupled with nonlinear power take-off dynamics. The proposed method is applied to a surface-riding wave energy converter, already optimized for single unit operation at individual sea states. Investigating two array layouts, linear and random, the optimized arrays after Step 1 increase the excitation spectral area by up to 40% relative to the single unit operation, indicating the synergy enhancing the first energy conversion. Subsequently, the dual-optimized linear layout attained a q-factor up to 1.13 in commonly occurring sea states, achieving improved average power generation in 60% of the evaluated sea states. The performance of the random layout exhibited the average power fluctuating along the wave spectra with a peak q-factor of 1.07. The individual adaptive resonance is confirmed in the optimized arrays, such that each surface-riding wave energy converter of both layouts adaptively resonates with the peak of the wave excitation spectra, maximizing the power generation for the different irregular waves. Full article

This research paper explores an approach to enhancing the economic viability of the heaving wave energy converters (WECs) of both cylinder-shaped and torus-shaped devices, by integrating them with four established, floating offshore wind turbines (FOWTs). Specifically, the approach focused on the wave power performance matrix. This integration of WECs and FOWTs not only offers the potential for shared construction and maintenance costs but also presents synergistic advantages in terms of power generation and platform stability. The study began by conducting a comprehensive review of the current State-of-the-Art in co-locating different types of WECs with various foundation platforms for FOWTs, taking into consideration the semi-submersible, spar and barge platforms commonly employed in the offshore wind industry. The research took a unified approach to investigate more and new WEC arrays, totaling 20 configurations across four distinct FOWTs. The scope of this study’s assumption primarily focused on the hydrodynamic wave power performance matrix, without the inclusion of aerodynamic loads. It then compared their outcomes to determine which array demonstrated superior wave energy under the key metrics of total absorbed power, capture width, and interaction factor. Additionally, the investigation could serve to reinforce the ongoing research and development efforts in the allocation of renewable energy resources. Full article

This paper develops a wave-to-wire model of a vibro-impact wave energy converter array for stand-alone offshore applications. Nonlinear model predictive control is proposed for maximising the wave power capture of the array, and implemented by AC/DC converters and the space vector pulse width modulation technique. A hybrid energy storage system, consisting of batteries and supercapacitors, is placed parallel to the DC bus via buck-boost DC/DC converters to smooth the array power output, and a Lyapunov-based power management strategy is utilised to control the DC/DC converters for stabilising the DC bus voltage. Intensive numerical simulations are conducted; the results show that the proposed wave-to-wire model is capable to evaluate the performance of the vibro-impact wave energy converter array in various scenarios, and the proposed energy maximisation control and power management strategy can enhance wave power capture and stabilise the power output simultaneously. Full article

The capability of the in-house transient wave-multibody computational tool, ITU-WAVE, is extended to predict the wave power absorption with Wave Energy Converters (WECs) arrays placed in front of a vertical breakwater. The hydrodynamic forces are approximated by solving boundary integral equation at each time interval. The reflection of incoming waves due to a vertical wall is predicted with method of images. The constructive or destructive performance of WECs arrays with different array configurations is measured with mean interaction factor. The behaviour of the hydrodynamic forces of each WEC due to a vertical wall effect shows considerable differences than those of WECs arrays without a vertical wall. When the wave power absorption with WECs arrays with and without a vertical wall effect are compared, the numerical results show that WECs placed in front of a vertical wall have much greater effects on wave power absorption. This can be attributed to the hydrodynamic interaction, standing waves, and nearly trapped waves in the gap between a vertical wall and WECs arrays. The analytical and other numerical results are used for the validation of present ITU-WAVE computational results for exciting and radiation forces, and mean interaction factor of WECs arrays which show satisfactory agreements. Full article

We developed a synergistic ocean renewable system where an array of Wave Energy Converters (WEC) with adaptive resonance was collocated with a Floating Offshore Wind Turbine (FOWT) such that the WECs, capturing wave energy through the resonance adapting to varying irregular waves, consequently reduced FOWFT loads and turbine motions. Combining Surface-Riding WECs (SR-WEC) individually designed to feasibly relocate their natural frequency at the peak of the wave excitation spectrum for each sea state, and to obtain the highest capture width ratio at one of the frequent sea states for annual average power in a tens of kilowatts scale with a 15 MW FOWT based on a semi-submersible, Bayesian Optimization is implemented to determine the arrangement of WECs that minimize the annual representation of FOWT’s wave excitation spectra. The time-domain simulation of the system in the optimized arrangement is performed, including two sets of interactions: one set is the wind turbine dynamics, mooring lines, and floating body dynamics for FOWT, and the other set is the nonlinear power-take-off dynamics, linear mooring, and individual WECs’ floating body dynamics. Those two sets of interactions are further coupled through the hydrodynamics of diffraction and radiation. For sea states comprising Annual Energy Production, we investigate the capture width ratio of WECs, wave excitation on FOWT, and nacelle acceleration of the turbine compared to their single unit operations. We find that the optimally arranged SR-WECs reduce the wave excitation spectral area of FOWT by up to 60% and lower the turbine’s peak nacelle acceleration by nearly 44% in highly occurring sea states, while multiple WECs often produce more than the single operation, achieving adaptive resonance with a larger wave excitation spectra for those sea states. The synergistic system improves the total Annual Energy Production (AEP) by 1440 MWh, and we address which costs of Levelized Cost Of Energy (LCOE) can be reduced by the collocation. Full article

Power electronic converters are an enabling technology for the emerging marine energy applications, such as using ocean waves to produce electricity. This paper outlines the power take-off system and its key components used in a wave energy converter offering modularity and scalability to generate power efficiently. The proposed power take-off system was implemented based on a modular multilevel converter and could be deployed to convert any alternating current electrical energy to a different alternating current for interconnection to grid or non-grid applications. Examples of widespread deployment are supplying electricity to coastal communities or producing clean drinking water. The analysis using both the simulation tests and laboratory experiments verified the design objectives and basic functionality of the developed power take-off system. An acceptable response using a field programmable gate array-based controlled laboratory testbench was achieved, complying with guidelines specified in the prevalent industry standards. Seamless operation during steady-state and transients for the studied wave energy converter was achieved as supported by the obtained results. The key findings of this work were experimentally examined under different load conditions, direct current bus voltage fluctuations, and generator speed–torque regulation. The ability of the power take-off system to generate high-power quality of the waveforms, e.g., against adhering to the IEEE 519-2022 standard for total harmonic distortion limits, is also confirmed. Full article

Thermoelectric nanoantennas have been extensively investigated due to their ability to directly convert infrared (IR) radiation into direct current without an additional rectification device. In this study, we introduce a thermoelectric nanoantenna geometry for maximum output voltage (V_oc) and propose an optimal series array configuration with a finite number of antennas to enhance the V_oc. A finite and open-ended SiO₂ substrate, with a thickness of a quarter-effective wavelength at a frequency of 28.3 THz, is used to generate standing waves within the substrate. An array of antennas is then positioned optimally on the substrate to maximize the temperature difference ($∆T$) between hot and cold areas, thereby increasing the average V_oc per antenna element. In numerical simulations, a linearly polarized incident wave with a power density of 1.42 W/cm² is applied to the structure. The results show that a single antenna with the optimum geometry on a substrate measuring 35 µm × 35 µm generates a $∆$T of 64.89 mK, corresponding to a V_oc of 1.75 µV. Finally, a series array of 5 × 6 thermoelectric nanoantennas on a 150 µm × 75 µm substrate including measurement pads achieves an average $∆$T of 49.60 mK with a total V_oc of 40.18 µV, resulting in an average V_oc of 1.34 µV per antenna element and a voltage responsivity (β_v) of 0.77 V/W. This value, achieved solely by optimizing the antenna geometry and open-ended substrate, matches or exceeds the V_oc and β_v of approximately 1 µV and 0.66 V/W, respectively, from suspended thermoelectric antenna arrays over air cavities. Therefore, the proposed thermoelectric nanoantenna array device, characterized by high stability and ease of fabrication, is suitable for manufacturing massive nanoantenna arrays for high-output IR-DC energy harvesters. Full article

This study examines the impact of the spacing parameter on the efficacy of an array of hybrid modules functioning as both floating breakwaters and wave energy converters. The dual functionality is ensured by the ability of the device to autoadjust its submergence. The behavior of multiple 1:40 scaled modules was tested in the wave tank of the University of Campania “Luigi Vanvitelli”. The objective was to assess the hydraulic performance of the array by analyzing transmission, reflection, and dissipation coefficients under different wave conditions. Specifically, the transmission coefficient ranges between 0.85 and 0.51, depending on the relative wavelength and wave steepness, while the reflection and dissipation coefficients vary, respectively, between 0.70–0.20 and 0.55–0.3. In any case, the results underscore the critical importance of the spacing parameter. Full article

Interactions between wave energy converters (WECs) can significantly affect the overall energy-harnessing performance of a wave park. Although large-size wave parks with many WEC units are commonly considered in practical applications, it is challenging to simulate such parks due to huge computational costs. This paper presents a numerical model that uses the boundary element method (BEM) to simulate wave parks. Each wave energy converter (WEC) was modelled as a comprehensive system, including WEC buoys, power take-off, and mooring systems, with hydrodynamic interactions included. Two classical layouts for arranging 16 units were simulated using this numerical model. The energy-harnessing performance of these array layouts was analyzed for both regular waves and a selection of irregular sea state conditions with different wave directions, wave heights, wave periods and water depths. For each layout, three WEC separation distances were studied. An increase of up to 16% in the power performance of the WEC under regular waves was observed, which highlights the importance of interaction effects. Full article