Wave Farm Research Articles

Theoretical modeling of a co-located system with a floating wind platform and vertical truncated cylinders array

Combined floating offshore wind turbines (FOWTs), wave energy converters (WECs), and floating solar photovoltaics (FPVs) systems have the potential to provide cost-effective solutions for offshore multi-energy complementation and structure protection. In this study, a theoretical model based on the potential flow theory and eigenfunction matching method is utilized to study wave diffraction and radiation by a co-located system, in which the main components of the wind platform and WECs are made of vertical cylindrical floats. Based on the displacement constraint matrix, coupled equations of motion are developed to calculate the kinematic response of the co-located systems. After running the convergence analysis and model validation, the present model is employed to perform a multiparameter impact analysis. Case studies are presented to clarify the effects of the WEC radius, draft, layout, power take-off (PTO) system, and incident wave heading and frequency on the hydrodynamic coefficient, wave energy capture width, and motion response of the wind platform. Our findings highlight that several factors play a crucial role in the performance of the co-located system, more importantly, that the theoretical model developed in this study is capable of effectively predicting the wave-structure interactions in wave fields, making it applicable to future wave farm projects.

Centralized control of a Wave Energy Farm

As long as an increased number of Wave Energy Converters are reaching their prototypal and pre-commercial stage it is fundamental to analyse in detail the issues arising from the grid integration of such devices. Point absorbers are among the most promising Wave Energy Converters. In this paper a point absorbers wave farm, connected to a weak grid, is simulated in order to evaluate how active and reactive power control strategies can help to fulfil the grid codes and to improve the behaviour of the farm as well as the efficiency of the internal grid. The real test case offered by bimep is used to model the internal grid of the farm. Different farm level control strategies, centralized and decentralized, are considered and compared. Both steady-state and dynamic analyses are carried out in order to assess the performance of the farm under its nominal operation and also to underline the detrimental effect of the energy source intermittency. Fault analyses are performed to evaluate the effect of voltage dips on the system operation.

Study on energy conversion efficiency of wave generation in shake plate mode

In recent years, increasing attention has been paid to factors affecting the efficiency of converting wave energy from kinetic energy using shake plates. This research was based on the volume of fluid method to evaluate the energy conversion efficiency of waves generated in the shake plate mode. The effects of different shake plate parameters and water depths on the kinetic energy conversion efficiency were studied, and the results agreed well with experimental data. Results indicated that the angular velocity of the shake plate had the highest influence on kinetic energy conversion efficiency. In the range of ωx to 1.8ωx, the maximum kinetic energy conversion efficiency was 52.1 %. The influence of the oscillation amplitude of the shake plate on the kinetic energy conversion rate was relatively low. As a result, the kinetic energy conversion efficiency remained at approximately 18.10 % even with changes in oscillation amplitude. The kinetic energy conversion efficiency of the shake plate increased with an increase in water depth, with maximum increase 87.39 % seen between 0.15 and 0.2 m. Our research is expected to serve as a reference for the implementation of efficient wave energy generation systems worldwide.

Development of Small-Scale Facilities for Initiating Studies into Sea Wave Energy Generation.

This paper describes the preliminary work carried out within the Civil and Electronics and Electrical Engineering Departments of The University of Glasgow. Two experimental pieces of equipment are described; the first is a piston-type of device suitable for testing small turbines in an oscillating water column system. The second is the conversion of a water flume into a wave tank for use in tests of small wave generator models and wave prediction systems.

Economic viability of floating wave power farms considering the energy generated in the near future

This article aims to analyse the economic viability of floating wave energy farms for the present and the next twenty years. The energy potential of the waves mainly depends on the climate, so the current and near future analysis is crucial to determine the economic viability of wave energy farms in a particular location. Current and near future wave resources were considered to assess the main parameters (Net Present Value (NPV), Internal Rate of Return (IRR) and Levelized Cost of Energy (LCOE)) that allow to know the economic feasibility of wave energy farms. This study takes one step forward in determining the economic evaluation of wave energy farms located in deep waters using their future energy projections. The case of study in this paper is the Atlantic coast of the Iberian Peninsula. Results indicate that the future wave energy reduction principally affects the NPV and LCOE of the wave farm.

Control Strategy Development for an Inverter Controlled Wave Energy Plant.

This paper will introduce the Energetech wave energy conversion system and describe its main elements of structure, turbine, generator, instrumentation and control systems. The concept of a parabolic wall which focuses the wave energy onto an oscillating water column (OWC) will be shown. The OWC converts the wave motion to pneumatic energy and then to kinetic energy in air flows suitable for mechanical conversion by the Energetech variable pitch turbine. The paper will show the main points of the station design which is due to have its first pilot plant commissioned by end 2004, 100km south of Sydney, Australia. The paper will describe the development of a wave to wire simulation used to rapidly test various station configurations and control scenarios. The model described will be shown as the result of several years of rigorous study involving scale systems, tank testing and computational fluid dynamics. Finally, the use of an inverter controlled variable speed drive will be discussed as the means of power take-off for the Energetech turbine. The control strategies developed using this system and their application in wave energy will be presented using the results of the wave to wire simulation.

Research on combined power generation of wave energy and wind energy

Research on combined power generation of wave energy and wind energy

Quantification of the Wave Energy Potential of the Atlantic Coast of Honduras

The growing demand for electricity in Honduras became a critical problem in 2022, evidencing an increase of 3.05%. This situation generated difficulties in the energy supply, and an increase of 10% to 15% in the cost of electricity was projected for the next quarter of 2023. Despite the efforts in renewable energies, the wave energy potential generated by the Atlantic waves is limited due to the lack of research in Honduras. To obtain a wave energy potential, meteorological data was collected on the swell, including wave height and wave interval, taking into account other factors such as density and sea depth. For this process, A variety of available resources were used, such as web scraping programming made in Python, and the data were obtained using the online software Windfinder. These were stored in Microsoft Excel, and mathematical models such as wave energy power and wave power formula were used, which considered parameters such as wave height and wave intervals. In addition, Airy’s theory equation was applied, taking into account the depth; these models allowed calculating the wave energy potential and comparing the results. Preliminary results indicate that the wave energy generation potential varies according to the model used, with the first model, wave energy power, varying 51%, the second, wave power formula, 46%, and Airy’s theory equation. This research was done to quantify the wave energy potential in the country of Honduras, specific to the Atlantic coast on the coasts of the departments of Cortés, Atlántida, Colón, Gracias a Dios, and Islas de la Bahía over a period of 10 weeks and contribute to future research.

The effect of pump diameter and penstock pipe on the electric power of a hybrid generator

Ocean Wave Power Plants (WEC) are divided into 6 types, namely (1) Point Absorber, (2) Oscillating Water Column, (3) Pressure Differential Submerger, (4) Oscillating Wave Surge Converter, (5) Attenuator & Terminator, and ( 6) Removable Devices. The AquabuOY type is a type of Point Absorber type wave power generator. This type uses a long pump connected to a Pelton turbine and was developed by Finavera (Aquaenergy) Company of Canada. The AquabuOY system has a weakness in that the turbine rotation depends on the wave period that occurs. The slower the wave period occurs, the weaker the resulting turbine rotation, therefore it needs to be improved by adding a reservoir unit to obtain pressure. stability and puffiness of the unit so that the rotation produced in the turbine is much greater. With this addition, the generator will spin more quickly and stably. In addition, the addition of wind energy installed at the top of the unit means that the generator to be built will produce more energy, is more flexible, can be placed in shallow, medium or deep seas, does not require complicated foundations, is relatively cheap, is not affected by extreme weather. and can be used in all sea conditions just by attaching it to a ballast. This study examines the effect of pump diameter and outlet pipe diameter on the electrical power generated at a hybrid power plant. pump diameter variations of 8 inches, 10 inches, 12 inches and 14 inches. Variation of outlet pipe diameter 1 inch, 2 inch, 3 inch and 4 inch. In this paper, we will present a simulation of the calculation of electrical energy from wave power with variations in pontoon volume, pump diameter, and outlet pipe diameter to obtain the most optimal system size. while wind energy power generation is presented in a different pape. Calculation simulation results to get the most optimal pump diameter and outlet pipe diameter in the hybrid power plant system built.

Machine learning-based diagnosis in wave power plants for cost reduction using real measured experimental data: Mutriku Wave Power Plant

In comparison to wind farms, the relative scarcity of actual operational data from wave power plants has contributed to a significant research gap in the areas of wave farm forecasting and cost reduction. In this context, this manuscript presents a new Machine Learning-based Power Take-Off (PTO) diagnosis for wave energy generation farms which has the potential to serve as an extensive reference for other wave energy farms and offer substantial benefits to both investors and policymakers involved in the advancement of the emerging wave technologies. The suggested method has been employed at the Mutriku Wave Power Plant (WWP) to facilitate the implementation of predictive maintenance strategies and reduce the Levelized Cost of Energy (LCoE). Hence, the research study considers two main extraction methods, namely, Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA), used to select the most relevant features for OWC diagnosis. In addition, two classification methods have been considered: Support Vector Machine (SVM) and Multi-Layer Perceptron (MLP) Artificial Neural Network (ANN). The obtained data show that, although both methods allow to achieve an effective performance with an excellent degree of accuracy, the ANN-based method presents better results with 98% accuracy against 81% for the SVM when using PCA extraction method. Then, the developed classification-based OWC diagnosis has been used for the development of a predictive maintenance strategy at the Mutriku WPP, analyzing its impact on the economic indicators. The results indicate that, using the proposed predictive maintenance strategy, the OpEx may be decreased down to 17%, downtime may be decreased down to 55% and plant availability may be better up to 95%, leading to a 5% LCoE reduction.

Techno-economic assessment of offshore wind and hybrid wind–wave farms with energy storage systems

Ocean renewables (such as offshore wind and wave) are abundant and essential energy resources for supporting future emission-free targets. However, their energy intermittency and high cost have hindered commercialization and wide-scale implementations of these ocean energy technologies. This paper focuses on both issues and aims to increase the dispatchability of ocean energy farms by investigating the potential of a hybrid wind and wave energy platform with energy storage systems (ESS). This research introduces an innovative method to assess the necessary ESS capacity for offshore renewable energy farms, ensuring energy dispatchability to the local demand. In addition, the key criteria and the economic feasibility of deploying ESS in offshore energy farms are also discussed. A life-cycle cost model is presented that quantitatively compares different farm configurations, specifically a standalone offshore wind farm and a hybrid configuration incorporating both wind and wave generation systems. The results indicate that the combined wind and wave energy farm significantly reduces the ESS requirement and provides competitive lifecycle costs compared to the stand-alone wind energy farm, though the amount of these benefits vary on the local resource characteristics. The quantitative assessment presented in this study also provides realistic and practical justifications for combined energy farms that complement statistical conclusions derived from variability indexes in previous studies.

Cost-Effective Optimization of an Array of Wave Energy Converters in Front of a Vertical Seawall

The present paper focuses on investigating the cost-effective configuration of an array of wave energy converters (WECs) composed of vertical cylinders situated in front of a vertical seawall in irregular waves. First, the hydrodynamic calculations are performed using a WAMIT commercial code based on linear potential theory, where the influence of the vertical wall is incorporated using the method of image. The viscous damping experienced by the oscillating cylinder is considered through CFD simulations of a free decay test. A variety of parameters, including WEC diameter, number of WECs, and the spacing between them, are considered to determine an economically efficient WEC configuration. The design of the WEC configuration is aided by a cost indicator, defined as the ratio of the total submerged volume of the WEC to overall power capture. The cost-effective configuration of WECs is achieved when WECs are positioned in front of a vertical wall and the distance between them is kept short. It can be explained that the trapped waves formed between adjacent WECs as well as the standing waves in front of a seawall significantly intensify wave fields around WECs and consequently amplify the heave motion of each WEC. A cost-effective design strategy of WEC deployment enhances the wave energy greatly and, consequently, contributes to constructing the wave energy farm.

Future electricity production at Mutriku Wave Energy Plant estimated from CMIP6 wave climate projections (2015–2100)

Renewable marine energy sources are rapidly developing worldwide. With numerous operational marine power plants in existence, it is becoming increasingly important to explore their potential. Hence, this study aims to examine the impact of climate change on the future potential of wave energy. The case study was centred on the Mutriku Wave Energy Plant, situated in the Bay of Biscay in the northern region of the Iberian Peninsula.To accomplish this, this study investigated changes in wave energy from 2015 to 2100 by employing ERA5 data and an ensemble of CSIRO wave projections driven by six distinct models derived from CMIP6 model runs. Two were associated with the SSP1-2.6 pathway while the other four corresponded to the SSP5-8.5 pathway. The unidimensional wave variables were bias-corrected using the Quantile Matching (QM) technique, whereas the bidimensional variables were corrected using the Multivariate Bias Correction N-pdf (MBC N-pdf) technique. Subsequently, a self-organising map (SOM) technique was employed to classify daily sea type frequencies and power. Additionally, the Smirnov test was employed to determine whether the probability density functions derived from different datasets exhibited significant differences at a significance level of 0.05.The conclusions obtained indicate that energy production in the Bay of Biscay will remain stable in the late 21st Century. The daily frequencies of the sea type and power did not change significantly. This stability ensures consistent power generation, enabling the location to provide a reliable and consistent source of energy both currently and in the future.

An advanced geospatial assessment of the Levelised cost of energy (LCOE) for wave farms in Irish and western UK waters

With the climate crisis becoming an ever-growing concern, Europe is striving to reduce its energy related greenhouse gas emissions. On the western edge of this continent, wave energy is a logical future clean energy consideration for Ireland and the U.K. to help realise ambitious targets recently being set in policy. Yet to reach commercialisation, there is still much uncertainty surrounding the financial feasibility of wave farms in the region of interest, and where exactly the most feasible locations are likely to be. The Levelised Cost of Energy (LCOE) is the most commonly used metric in determining the financial feasibility of an energy project, and it is very much site dependant when it comes to wave energy, varying considerably from one location to the next. This study uses the geographic approach to address this and estimate the LCOE of wave energy farms in the region, considering different technology types and the geospatially variable inputs at play. The results reveal areas of high project feasibility in the Atlantic Ocean (off the west coast of Ireland), the Celtic Sea and the Inner Seas off the West Coast of Scotland (ISWCS), with LCOE values below 110€/MWh along the coasts of these areas.

Optimal array arrangement of oscillating wave surge converters: An analysis based on three devices

Wave farms consist of arrays of wave energy converters. However, ocean waves perturbed by one device will interact with its neighbouring devices, which can lead to more or less power yielded than operating the devices in isolation. Therefore, it is of significant interest to study the optimal layout and spacing to deploy multiple devices. In this work, a validated high-fidelity computational approach is used to study the optimal arrays of three oscillating wave surge converters by systematically varying the array arrangement in different wave conditions. The simulations demonstrate the wave interaction with multiple dynamic bodies and how this affects the overall power output. Furthermore, novel empirical rules are derived to design the optimal constructive layout for three devices in a given wave condition, and this can be extended to cases of numerous devices.

Scattering of water waves by multiple rows of vertical thin barriers

The reflection and transmission of waves by a periodic array of thin fixed identical vertical barriers extending uniformly through the depth of the fluid is considered. The water wave problem, which also has analogues in acoustics and electromagnetics, involves scattering by a large finite number of equally spaced rows, each consisting of an array of barriers with a linear periodic arrangement extending to infinity. The main purpose of the work is to compare the results of two approximate methods of solution based on homogenisation techniques with exact results allowing us to determine when the results can be expected to be in good agreement. When no approximation is made, a method of solution (Discrete Model) describing the propagation of incident waves through the exact barrier arrangement is derived using Floquet–Bloch eigensolutions for the corresponding infinite periodic array. It is shown how the solution can be reduced to a simple pair of integral equations which results only from matching the region containing barrier arrays to the two exterior domains. Numerical solutions are, nevertheless, relatively complicated and two approximate models are developed which considerably simplify the numerical effort required. In one approximation (Continuum Model I) it is assumed only that the spacing between two adjacent rows of barriers is small and is complementary to the commonly-used wide-spacing approximation. The complication of the geometry is removed by replacing the governing equations and boundary conditions with an effective continuous medium and a simplified pair of integral equations now govern the solutions. In a second approximation (Continuum Model II), a low-frequency homogenisation approach based on a long-wave assumption is invoked and matching now leads to closed-form expressions for the reflection and transmission coefficients. Results concentrate on the comparison between different methods which allows us to assess the validity of each continuum model. This understanding will be important in developing approximate models that describe the operation of wave energy farms consisting of large arrays of oscillating flaps designed to absorb energy.

Short-term wave power forecasting with hybrid multivariate variational mode decomposition model integrated with cascaded feedforward neural networks

Wave power is an emerging renewable energy technology that has not reached its full potential. For wave power plants, a reliable forecast system is crucial to managing intermittency. We propose a novel robust short-term wave power (Pw) forecasting method, MVMD-CFNN, based on a multivariate variational mode decomposition hybridized with cascaded feedforward neural networks. By using cross-correlation, we were able to determine the significant input predictor lags. To overcome the non-linearity and non-stationarity issues, the proposed MVMD method is then used to demarcate the significant lags into intrinsic mode functions (IMFs). To forecast the short-term PW, the MVMD-CFNN model incorporated the IMFs into cascaded feedforward neural networks. Validation and benchmarking of the MVMD-CFNN model at two stations in Queensland, Australia has been conducted against standalone cascaded feedforward neural networks, boosted regression trees, extreme learning machines, and hybrid models, MVMD-BRT and MVMD-ELM. According to the results, the MVMD-CFNN predicts PW accurately against the benchmark models. The outcomes of this research can contribute to the application and implementation of clean energy worldwide for sustainable energy generation.

Assessment of Wave Energy Converters Based on Historical Data from a Given Point in the Sea

The assessment of wave energy converters is a key issue for planning and managing the economic feasibility wave power plants. However, obtaining reliable assessments is a difficult goal due to the strong stochastic component of wave behaviour. This paper proposes a simple and straightforward assessment method based on empirical data to estimate not only the expected values of converted power, but also their confidence limits. The method combines Gaussian mixed models with the Monte Carlo method. The proposed approach was validated by assessing five converters with data obtained from two different buoys. The daily converted power values agree with the measured wave parameter patterns. Furthermore, all the observed values of monthly generated energy in the three years after the evaluation fell within the forecast intervals, supporting the validity of the proposed approach.

Consistent mapping of marine structures with an autonomous surface vehicle using motion compensation and submap-based filtering

Inspection and maintenance of marine energy farms are becoming increasingly important as more farms are developed and constructed. In this study, structural monitoring system using an autonomous surface vehicle (ASV) has been proposed to enable the inspection of an offshore power plant under harsh ocean disturbances. In particular, the ASV uses guidance and control laws to minimize the deviation from the desired path in waypoint tracking. The ASV was also equipped with multi-modal sensors – sonar and light detection and ranging (LiDAR) – for mapping underwater and surface structures. By utilizing the navigation sensors, the motion of the ASV in ocean disturbances was accurately estimated and incorporated into the mapping process to produce consistent multi-modal maps. Furthermore, dedicated outlier removal methods were proposed to improve the performance over conventional approaches in real offshore data. We considered the sparsity of the sonar and LiDAR data in their respective modality during acquisition and designed novel submap-based filtering to remove the outliers. To validate the proposed system, a field test was conducted on an offshore wave farm structure. It was verified that the ASV can cope with ocean disturbances in its waypoint tracking, and the resulting multi-modal maps are consistent and outlier-free.

Parametric Design of a New Float-Type Wave Energy Generator and Numerical Simulation of Its Hydrodynamic Performance

A novel float-type device for wave energy power generation, designed specifically for offshore wave environments, is introduced as an innovative technology in wave energy utilization. Herein, we present the design concept, structural composition, and energy conversion process of the device, and conduct mathematical modeling and theoretical research on its kinematic and dynamic characteristics. At the same time, we use a numerical wave pool based on the STAR-CCM+ boundary wave making method and damping dissipation method to analyze the motion response and output power of the wave energy generator in a five-order Stokes wave environment within one wave cycle and the entire operating cycle. Finally, in order to develop the best design strategy, we study the effect of changing the structural parameters of the power generation device on the hydrodynamic performance of the device.