Wave Energy Converter Research Articles

Techno-economic designs of hybrid wind-wave offshore energy systems and comparison with TOPSIS analysis: an Italian case study

This study assesses multiple hybrid wind and wave floating offshore systems, utilizing a preliminary approach for dimensioning and the TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) analysis method for comparison. It aims to provide an initial evaluation of diverse concepts, emphasizing state-of-the-art combinations of Floating offshore Wind Turbine (FOWT) with Wave Energy Converters (WECs). The criteria for evaluation include system cost, power extraction, WEC integration, dynamic and environmental responses, offering a comprehensive view of performance, economic viability, constructability, operational efficiency, and environmental impact. The findings, derived from the application of these methodologies, are informed by an Italian case study, enriching the insights and illustrating the practical implications of the evaluated hybrid systems within the Italian context. Preliminary results suggest a tendency for semi-submersible platforms to be more suitable for combined with WEC devices.

Numerical analysis of a projecting wall type oscillating water column (PW-OWC) wave energy converter in regular waves

Numerical analysis of a projecting wall type oscillating water column (PW-OWC) wave energy converter in regular waves

Evaluating the economic viability of near-future wave energy development along the Galician coast using LCoE analysis for multiple wave energy devices

The economic profitability of future wave energy production along the Galician coast is assessed by analyzing the Levelized Cost of Energy (LCoE) under different Capital Expenditure (CapEx) scenarios and two discounts rates (5% and 10%). Wave resources for the near future under the RCP8.5 scenario are downscaled using SWAN, providing up to 75 m spatial resolution in coastal areas. The study’s goal is to enhance the cost-effectiveness by selecting the most suitable wave energy converter (WEC) for each location. Fourteen WECs operating at different depths are considered. This analysis reveals that the Atargis device boasts the lowest LCoE for 64.2% of the coastal area, mainly in deep waters, with an LCoE of 77 €/MWh. In addition, the Oyster and Wave Dragon devices exhibit the lowest LCoE for 12.4% and 15.0% of the coastal area, respectively, excelling in shallow waters and near the coast, with values of 50 €/MWh and 97 €/MWh. These findings demonstrate the profitability of wave energy production along the Galician coast, even when considering a more conservative CapEx of 3 M€/MW, resulting in a cost of 140 €/MWh. This conclusion takes into account the evolving electricity prices in Spain, which reached 0.2068 €/kWh in the second half of 2023.

Comparing Open-Source BEM solvers for analysing wave energy converters

Comparing Open-Source BEM solvers for analysing wave energy converters

Numerical investigation of the hydrodynamic properties of oscillating water column air chambers

Abstract The oceans occupy nearly 71% of the Earth’s surface area. The ocean is rich in energy, and wave energy is one of its important components. Therefore, the study of wave energy generation devices is an important issue. In this paper, we analyze the effect of the size of the air chamber structure on the OWC (oscillating water column) wave energy conversion device under the action of unidirectional regular waves. To analyze the performance of the OWC device under real sea conditions, the wave climate at Sanmenxia is used as the experimental parameter. The performance and characteristic response with the variation of incident wave height, air chamber width and front wall thickness, are analyzed. The results show that the incident wave height, air chamber width, and front wall draft have significant effects on the performance of OWC. With the increase of incident wave height, the wave nonlinear effect increases. As the air chamber width decreases, the horizontal surface inside the air chamber undulates smoothly and the standing wave phenomenon disappears.

An innovative dry-lab test rig for mechanical-hydraulic power take-off of wave energy conversion system

A dry-lab test rig is a powerful means to reduce costs in the design process of a wave energy conversion system (WECs). A dry-lab test rig technique allows the use of real components inside a simulation of a mathematical model. This paper presents the development of an innovative dry-lab test rig for the mechanicalhydraulic power take-off (MHPTO) unit of WECs. The development of a drylab test rig of MHPTO involves several processes, such as three-dimension (3D) modelling, component purchasing, structure fabrication, component installation, and operational testing. The developed dry-lab test rig consists of two main parts, such as the simulated wave emulator plant and the real MHPTO unit plant. The simulated wave emulator plant was developed in this test rig to replicate the interaction motion between the ocean wave motion and the wave absorber device. The developed dry-lab test rig was tested using five different irregular wave input conditions to ensure it could perform under the five different wave input conditions. The overall results demonstrate that the developed dry-lab test rig was successfully performed in all sea states. From the results, the profile of electrical power produced by the real MHPTO unit can be clearly obtained in each sea state.

A Novel Consequent-Pole Magnetic Lead Screw and its 3-D Analytical Model With Experimental Verification for Wave Energy Conversion

A Novel Consequent-Pole Magnetic Lead Screw and its 3-D Analytical Model With Experimental Verification for Wave Energy Conversion

Electrostatic Wave Energy Conversion: A Review of Devices, Theory, and Hurdles

Electrostatic Wave Energy Conversion: A Review of Devices, Theory, and Hurdles

Experimental Study on Spacing Effect in Arrays of Draft-Varying Floating WEC-Dikes

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.

Optimizing wave energy harvesting through oscillating water columns in semi-submersible energy harvesting platforms: A comprehensive study on enhancing efficiency and competitiveness

In coastal regions with substantial wave energy potential, significant efforts have been dedicated to advancing both the Technology Readiness Level (TRL) and Technology Performance Level (TPL) of Wave Energy Converters (WECs). Despite their promising energy generation capabilities, the widespread adoption of WEC devices faces a notable challenge in the form of their relatively high Levelized Cost of Energy (LCOE). This economic hurdle hampers their competitiveness when compared to conventional fossil fuels and other renewable energy sources. Oscillating Water Columns (OWCs) stand out due to their noteworthy potential, primarily attributed to their low Operations and Maintenance (O&M) costs. To enhance the energy performance of OWC arrays and pave the way for hybrid offshore energy solutions, the integration of a semi-submersible Energy Harvesting Platform (EHP) is proposed. This integration involves configuring the array with specific OWC End-Stop limitations and geometry to establish resonant conditions during the predominant wave, thereby optimizing constructive interactions and desirable OWC motion with the EHP's heave, pitch, and roll. A Genetic Algorithm (GA) is employed for this optimization process. Additionally, a novel parameter, the In Situ Interaction Factor (ISIF) is introduced, to evaluate the EHP's power capture performance. This metric compares the actual energy harvested from the array of WECs on the platform to the cumulative energy harvested by each device in isolation. Notably, ISIF achieved a remarkable value of 1.99, highlighting the highly efficient constructive interaction achieved through the precise positioning of OWCs. This resulted in nearly doubling the power capture compared to 23 OWCs operating in isolation, underscoring the potential of the EHP in harnessing wave energy. Validation of the analytical analysis was conducted using the open-source Boundary Element Method (BEM) tool NEMOH, alongside reference to the experimental studies.

Implementation of machine learning techniques for the analysis of wave energy conversion systems: a comprehensive review

Implementation of machine learning techniques for the analysis of wave energy conversion systems: a comprehensive review

Experimental Validation of the Capture Chamber Model in Mutriku MOWC Wave Power Plant

Wave energy holds the potential to fulfill 15% of the EU's energy demand by 2050, thereby reducing CO2 emissions by 136 million metric tons per megawatt-hour, as outlined in the EU Energy Road Map. Similarly, the Spanish Renewable Energies Plan underscores the significant marine energy potential in Spain, particularly emphasizing wave energy. Within this framework, Oscillating Water Column (OWC) converters currently stand as among the most promising wave energy conversion technologies, offering the capability to harness ocean energy from various on-shore and floating structures. This paper introduces an analytical model of the wave capture chamber parameterized for a specific on-shore OWC wave power plant. The model is specifically adapted and parameterized for the Mutriku Marine Offshore Wave Power Plant located on the coast of the Spanish Basque Country. Subsequently, validation is conducted using both real wave entry data measured on-site and experimental output power data generated in the plant.

Theoretical modeling of a bottom-raised oscillating surge wave energy converter structural loadings and power performances

This study presents theoretical formulations to evaluate the fundamental parameters and performance characteristics of a bottom-raised oscillating surge wave energy converter (OSWEC) device. Employing a flat plate assumption and potential flow formulation in elliptical coordinates, closed-form equations for the added mass, radiation damping, and excitation forces/torques in the relevant pitch-pitch and surge-pitch directions of motion are developed and used to calculate the system's response amplitude operator and the forces and moments acting on the foundation. The model is benchmarked against numerical simulations using WAMIT and WEC-Sim, showcasing excellent agreement. The sensitivity of plate thickness on the analytical hydrodynamic solutions is investigated over several thickness-to-width ratios ranging from 1:80 to 1:10. The results show that as the thickness of the benchmark OSWEC increases, the deviation of the analytical hydrodynamic coefficients from the numerical solutions grows from 3 % to 25 %. Differences in the excitation forces and torques, however, are contained within 12 %. While the flat plate assumption is a limitation of the proposed analytical model, the error is within a reasonable margin for use in the design space exploration phase before a higher-fidelity (and thus more computationally expensive) model is employed. A parametric study demonstrates the ability of the analytical model to quickly sweep over a domain of OSWEC dimensions, illustrating the analytical model's utility in the early phases of design.

Wave energy converter arrays: A methodology to assess performance considering the disturbed wave field

Wave Energy Converters (WECs) often face power fluctuations due to wave variability, making grid integration costly. To mitigate this, placing multiple WECs in an array can reduce both power variability and expenses. Prior research has limited consideration of the impact of individual WECs on the disturbed wave field. Therefore, a novel simulation framework is proposed which is capable of evaluating the disturbed wave field by coupling a time domain hydrodynamics solver (ProteusDS) and a spectral wave field propagation model (Simulating WAves Nearshore (SWAN)).Numerical simulations are conducted for three different WEC archetypes (RM3, RM5, and Triton) under four representative sea states. The framework is compared with two lower-fidelity models to highlight key array effects. Results show that (a) placing WECs in an array significantly improves power quality (e.g., Triton reduces CoV by up to 37%); (b) WECs notably impact the wave field (e.g., RM3 up to 14%, RM5 up to 39%, Triton up to 29% diffraction); (c) Wave refraction, alongside attenuation, is crucial, or array power may be underpredicted (e.g., RM5 by 40% and Triton by 26%); (d) Constructive array effects can be found (e.g., Triton Q-factor up to 1.07) even without optimization, emphasizing the potential for further improvements.

Wave energy converter with mechanical motion rectifier, motion regulator, and energy storage element.

In this work, a novel design of an oscillating body-type Wave Energy Converter (WEC) is proposed with an efficiency of 48.73 %. Innovative features of the new design include the integration of Mechanical Motion Rectifier (MMR), Motion Regulator (MR), Energy Storage Element (ESE), and Electric Generator (EG) with the operation controlled by a microcontroller, limit switches, and linear actuator. Lab experiments conducted with a prototype ensured a peak voltage of 8.1 V and peak power of 4.3 W. Experimental and MATLAB theoretical simulation results demonstrated the average power of 55.2-148.3 mW for a wave height of 50-125 mm. In comparison to the conventional operation, where the electric generator is directly driven by wave motion, the proposed design will ensure higher peak power and better energy utilization characteristics of the generated voltage waveform. Simulation results are presented with the incorporation of non-circular gears that ensure modification of the voltage waveform for better energy utilization.

Impact of Wave Energy Converters and Port Layout on Coastal Dynamics: Case Study of Astara Port

In the face of depleting fossil energy and the imperative of sustainable development, there is a compelling drive towards advancing renewable energies. In this context, sustainable and predictable alternatives, like marine energy, gain prominence. Marine energy presents a cleaner option devoid of the adverse effects associated with fossil fuels, playing a crucial role in environmental sustainability by safeguarding coastlines against erosion. This study focuses on Astara Port in the Caspian Sea, exploring the utilization of wave energy converters (WECs). The originality of this study’s research lies in exploring WECs’ dual role in energy generation and coastal protection. Using MIKE21 software simulations, the impact of number, location, arrangement, and orientation of WECs across various scenarios was investigated, including two WEC number scenarios (11 and 13), three structural placement scenarios (north, front, and south of the port), two structural arrangement scenarios (linear and staggered), two port layout scenarios (original layout and modified layout), and two orientation scenarios for the structures (facing north-east, which is the dominant wave direction, and facing southeast). The results show a remarkable decrease in the significant wave height behind WECs, notably with 13 staggered devices facing dominant waves (from northeast), reducing the significant wave height Hs by 23–25%. This setup also shows the highest wave height reduction, notably 36.26% during a storm event. However, linear WEC setup offers more extensive coastline protection, covering 47.88% of the model boundary during storms. Furthermore, the 11 staggered WECs facing southeast (SE) arrangement had the lowest sediment accumulation at 0.0358 m over one year, showing effective sedimentation mitigation potential. Conversely, the 13 linear WECs facing northeast (NE) had the highest accumulation at 0.1231 m. Finally, the proposed port design redirects high-velocity flow away from the port entrance and removes rotatory flow, reducing sediment accumulation near the harbor entrance.

Finding the best shape of floating wave energy converters for different primary geometries: Experimental and numerical investigations

This research aimed to identify the optimal geometry for maximizing wave energy extraction from wave energy converters (WECs) by employing different primary geometries of floating bodies (specifically, cube, cylinder, and sphere). Laboratory experiments were conducted using a wave tank to generate waves with varying characteristics. The floats were subjected to waves of different wave conditions, including height (4 cm, 6 cm, and 9 cm) and frequency (0.9 Hz and 0.83 Hz). Multiple probes and sensors were used to collect experimental data. The results revealed that when hit by a wave with a height of 9 cm and a frequency of 0.9 Hz, the rectangular cube experienced an average displacement of 12 cm and 14 cm along its length, with the same weight and draft, respectively. Furthermore, comparisons of the experimental data across different scenarios indicated that the rectangular cube, elongated perpendicular to the incident waves, performed well in most of the test cases. The efficiency of primary wave energy conversion was evaluated for all floated bodies and wave conditions, encompassing a range of values from 0.02 to 0.34. Additionally, numerical simulations of wave and float displacement demonstrated good agreement with the experimental observations.

The role of size and inertia on the hydrodynamics of a self-reacting heave single point absorber wave energy converter

We propose a detailed numerical study of a self-reacting floating point absorber, resembling the Ocean Power Technologies device PB3 PowerBuoy, for a possible installation in the Adriatic Sea. A simplified model of the mentioned device, composed of a floater sliding along a reacting body, which supports the floater, is studied, reproducing and analysing the most complex nonlinear phenomena, such as the wave overtopping and the out-of-water motion of the floater. Three different sizes of the device have been simulated, each with three different masses of the floater, deriving the time evolution of the wave in the surrounding of the floater, its frequency dispersion and energy content, the generated exciting force, the wave overtopping over the floater, and the out-of-water motion of the floater. The results highlight that the linear response is favoured by small floater density and optimal floater thickness. Additionally, large-sized devices are characterized by linear, but dissipative, response, while the response of medium-sized devices is only apparently linear.

An optimization approach for geometry design of multi-axis wave energy converter

The current global energy crisis necessitates a shift to renewable energy sources to mitigate climate change impacts. Wave energy emerges as a promising renewable resource to fulfill increasing energy demands. This energy can be extracted using wave energy converters (WECs), with multi-axis WECs (MA-WECs) being more effective than single-axis versions due to their capacity to harness energy from waves in various directions. The challenge lies in determining the ideal geometric design for MA-WECs, that can be tackled through multi-objective optimization (MOO) techniques. This research focuses on evaluating different MOO algorithms for the optimal geometric design of MA-WECs. To assess the structural response of different geometries and sizes, the study utilized the NEMOH boundary element method solver, aiming to maximize power output, lower the levelized cost of energy (LCOE), and optimize the geometry configuration. Findings indicate that the choice of optimization algorithm considerably influences the MA-WEC's optimal design, enhancing power efficiency, reducing device volume, and cutting costs more effectively than the initial design.

Numerical investigation of the response of the hybrid wave energy converter including oscillating water column and horizontal floating cylinder to irregular waves

The main goal of this research is to investigate the effect of some geometrical parameters on an onshore Hybrid Wave Energy Converter (HWEC) including an onshore Oscillating Water Column (OWC) and a Horizontal Floating Cylinder (HFC) under regular and irregular waves. The TMA spectrum is the basis of this study. The wave spectrum is used to generate irregular waves in a numerical wave tank using Ansys-fluent software based on URANS equations. Active wave absorption is used to avoid the effect of reflected waves. Also, the SST k−ω turbulence model and the VOF scheme are used for turbulence modeling and interface tracking, respectively. The results confirm that the efficiency of the HWEC is higher than the efficiency of an OWC and the efficiency of an HFC in both regular and irregular waves. Besides, the efficiency of the HWEC in irregular waves is lower than its efficiency in regular waves. A comparison of the TMA and JONSWAP spectrum on HWEC performance shows that HWEC performance is lower on the JOANSWAP spectrum. This study shows that the use of irregular waves is essential to obtain more realistic results from analyses of the onshore HWEC performance, despite their need for high computational cost.